chapter 10 Intramuscular Sedation
The intramuscular (IM) route of drug administration is a parenteral technique in which the drug enters the cardiovascular system without first passing through the gastrointestinal (GI) tract. Parenteral techniques possess an advantage over enteral techniques (oral, rectal) in that the drug does not first have to pass through the enterohepatic circulation before entering the systemic circulation. This eliminates several disadvantages of enteral routes, including a possible hepatic first-pass effect, presence of food in the stomach, and delayed gastric emptying. The advantages and disadvantages of the IM route were discussed in Chapter 3 and are summarized in Box 10-1.
Advantages/Disadvantages of Intramuscular Drug Administration
Probably the most significant negative aspect of using the IM route is an inability to titrate the drug to a desired clinical effect. The dentist is unable to consistently predict the proper dose to administer in any given patient, leading to the use of an “educated guesstimate” based on a number of factors to be discussed shortly. Although the dose is often appropriate, situations occur in which the calculated dose proves ineffective, leading to an inability to treat the patient. More significant, however, are those occasions when the calculated dose has proven too great for the patient, leading to possibly dire consequences for both the patient and the dentist.1–4
The IM route of drug administration is indicated for use in almost any patient; however, several factors must be considered in determining the depth of sedation that can (and should) safely be sought via this route. As mentioned, inability to titrate is a prime negative consideration, as is the inability to rapidly reverse the actions of the drug.
The last factor, the administration of emergency drugs, is the reason I believe that all dental personnel should be trained to administer drugs intramuscularly. Although IV drug administration is more rapidly effective, in an emergency situation, the IM route may be the only practical route immediately available.
The level of central nervous system (CNS) depression sought via the IM route will vary considerably, from lighter levels of anxiolysis (minimal sedation), in a frightened but otherwise healthy adult, to deeper levels of sedation (in the unmanageable child or adult or patient with a disability in whom the only alternative to IM sedation is general anesthesia). It must be stated here (as it is repeatedly throughout this text) that the dentist administering drugs to a patient must know his or her limitations in drug usage. Important factors in deciding the depth of sedation to which a patient may safely be brought include (1) the physical status of the patient, (2) the training of the dentist and staff, and (3) the availability of trained personnel and equipment for the prompt and effective management of any emergency situation that might conceivably arise as a result of the use of a drug or coincident with its use, the concept of “rescue” from a more profound level of CNS depression than that sought. Deep sedation must not be employed by a dentist who is not well versed in the art and science of anesthesiology and in the management of the unconscious airway.
All 50 states in the United States require a dentist employing parenteral (IM/IN/IV) sedation to obtain a special permit from the state board of dental examiners. State requirements for parenteral sedation permits vary, but take into account the degree of education in the technique, preparedness for emergencies, and demonstrated clinical proficiency.5
In the healthy adult, there are few indications for IM sedation. Most adults, although not “liking it,” will tolerate an IM injection of a drug. If the patient can psychologically tolerate this traumatic event (the “sticking of a needle into the skin”), the IV route of administration is preferred. The IV route is more controllable than is the IM route. If a needle is to be inserted into a patient’s body for the purpose of administering a CNS-depressant drug, it is much preferred, for reasons of safety and effectiveness, to administer such drugs intravenously. IV administration offers immensely more control over the drug’s actions, and in many cases, unwanted reactions to the drug can be quickly reversed (e.g., with the IV administration of naloxone or flumazenil). In the absence of superficial veins, elective venipuncture and IV moderate sedation are contraindicated; the inability to breathe through the nose or adverse clinical experience in the past with inhalation sedation contraindicates nitrous oxide-oxygen (N2O-O2). In these situations, IM moderate sedation in an adult patient should receive serious consideration.
In the child, the IM route is more frequently indicated. Both IV and inhalation moderate sedation require a degree of patient cooperation to be successful. The overtly disruptive child will neither permit a venipuncture nor allow a nasal hood to be placed and maintained over his or her nose, thereby dooming these two valuable techniques to failure. In such a situation, the IM route may be the only sedative route with any likelihood of success. Failure of the IM technique most likely means that the patient will have to receive dental care under general anesthesia.
Some patients with physical or mental disabilities, both pediatric and adult, are unable to tolerate dental care in the usual manner and are therefore candidates for sedative techniques. Although many of these patients are manageable with oral, inhalation, or IV moderate sedation, disruptive patients with disabilities may require IM drug administration as a means of calming them before the use of other, more controllable sedation techniques.
Another use of the IM route in dentistry is the administration of nonsedative drugs. These drugs may also be administered orally or rectally; however, because of the greatly increased reliability of absorption and greater efficacy noted with the IM route, this technique should be considered when these drugs are used. Drugs commonly administered via this route are the anticholinergics (atropine, scopolamine, glycopyrrolate) and the antiemetics (ondansetron [Zofran], promethazine). These drugs are discussed later in this chapter. The suggested uses of IM drug administration in dentistry are presented in Box 10-2.
Recommended Use of the Intramuscular Route
A variation on IM drug administration called submucosal (SM) administration has been used in pediatric dentistry.6 In the SM technique, a CNS-depressant drug is injected into the mucous membrane in either the maxillary or mandibular buccal fold. An advantage of SM administration over IM administration is a slightly more rapid onset of clinical action.7,8 However, this same rapid onset of action may also be associated with a more rapid appearance of undesirable drug actions, such as respiratory depression. As originally developed, the SM route was used for the administration of opioid agonists (OAs), such as alphaprodine.9 The technique has fallen into disrepute because of a significant number of serious adverse reactions that were noted in conjunction with the SM administration of alphaprodine.1–36 The SM route is discussed in greater detail in Chapter 35.
Four sites are available for IM drug administration.10–12 Proper site selection varies from patient to patient and is an important factor in the safety of this technique. The sites most commonly chosen for the administration of IM drugs are the following:
The upper outer quadrant of the gluteal region is the most commonly used site for IM drug administration in adults.13 The gluteus maximus is the muscle most commonly injected.
The gluteal region extends superiorly to the anterior superior iliac spine (Figure 10-1). With this as a landmark, the region is divided into quadrants. The upper outer quadrant is the most anatomically safe because it is distant from the sciatic nerve and the superior gluteal artery.14 The lower inner aspect of the upper outer quadrant is the preferred site within this quadrant.
Figure 10-1 Gluteal region, divided into quadrants. The upper outer quadrant is the recommended site for IM injection. Lines A and A’ represent boundaries in classic IM technique. Line B demonstrates the ease with which a landmark may be displaced, increasing the risk of sciatic nerve injury.
The gluteal region in the adult can accept 4 to 8 ml of solution.11,14 In addition, the skin of this region is relatively thin and is more easily penetrated by the needle.
The upper inner quadrant is unacceptable as an IM injection site because it contains the roots of the sacral plexus. The lower inner quadrant contains the sciatic nerve. Ceravolo et al13 report a nerve injury rate of up to 8% following IM injection into the gluteal region.
For injection into the upper outer quadrant, the patient should be lying face down on a bed or examining table with the toes in and arms hanging off the table.15 This permits maximal relaxation. Although this site is also used with the patient standing, it is not as highly recommended because the muscles do not relax as well in this position. Muscle tissue that is contracted does not accommodate the injected fluid, forcing it upward into the subcutaneous tissues, where absorption is less reliable and slower and where certain chemicals are more likely to produce tissue irritation and damage. In addition, the administration of IM drugs into contracted muscle is thought to be more uncomfortable than IM injection into relaxed muscle.12
Of the four available IM injection sites, the gluteal region is the least well perfused, having 20% lower perfusion than the deltoid.16 Because perfusion is the rate-limiting step in the absorption of IM drugs, the rate of onset of action of drugs administered in the gluteal region is somewhat slower than when alternative sites are used.11,14
The gluteal region requires a degree of patient disrobing for the injection to be properly administered. This may, in some instances, limit the utility of the gluteal region in the adult patient within the dental office; however, with assistance from the parent or guardian, this site may readily be employed in the pediatric patient with little or no loss of modesty.
The site is located among three bony landmarks that are usually quite readily palpated. These are the anterior superior iliac spine, the iliac crest, and the greater trochanter of the femur. Anatomically, this region lies at some distance from the sciatic nerve and other anatomically important structures.15
For this site to be properly used, the anterior superior iliac spine is located with the tip of the index finger (Figure 10-2). The left hand is pressed onto the hip with the palm of the hand over the greater trochanter and the fingers pointed toward the patient’s head. The index and middle fingers are spread as far as possible, forming a V, with the tip of the ventrally placed finger pressed down on the soft tissue over the anterior superior iliac spine, preventing movement of the skin. The needle puncture is made between these fingers and aimed just below the iliac crest.
Figure 10-2 Ventrogluteal region. Index finger locates anterior iliac spine; index and middle fingers spread apart forming a V. Needle puncture occurs between fingers (X) and is aimed toward the iliac crest.
The ventrogluteal region in an adult is capable of managing 4 to 8 ml of solution. This site is rarely used in the typical dental office situation. Where bedridden patients are treated, this IM site warrants consideration.
The anterior aspect of the thigh is probably the safest region in which to deposit IM drugs. Although not of consequence in the typical dental situation, the vastus lateralis can accommodate volumes of solution up to 15 ml, whereas the gluteal and ventrogluteal can accommodate approximately 4 to 8 ml each before muscle distortion and dissection occur, leading to increased pain during and after injection.
The site for injection in the vastus lateralis muscle is a narrow rectangular band running along the anterior lateral aspect of the thigh (Figure 10-3). The region begins approximately one handbreadth above the knee and runs to the same distance below the greater trochanter of the femur.15
Anatomically the vastus lateralis site contains no structures of importance (Figure 10-4). Overly deep penetration of the needle may strike the femur, resulting in discomfort and possible needle breakage. All significant anatomic structures are located on the medial and posterior aspects of the thigh (the femoral artery and vein and the sciatic nerve).
This site is strongly recommended for use in small children.11 Injection in the gluteal muscles is contraindicated in children who have not yet begun to walk because of the lack of maturity and development of their gluteal musculature. The gluteal region ought not to be chosen until at least 1 full year after the child has begun to walk.17
Some degree of disrobing is required when the vastus lateralis site is used. The site is more readily accessible in the woman wearing a skirt or dress, but it is of absolute importance that a female assistant be present with the dentist in the treatment room throughout the time that the injection is given. In any patient wearing pants or slacks, a greater degree of disrobing is required, a fact that might discourage use of this site. In the pediatric patient, the vastus lateralis may readily be employed with assistance from the patient’s parent or guardian.
In adult or larger pediatric patients who are unmanageable (e.g., combative) and when IM drug administration is considered mandatory, IM injection into the vastus lateralis muscle through the patient’s clothing is appropriate. Although sterile technique cannot be maintained in this situation, it is unlikely that complications will be noted. This consideration is of special importance when a life-threatening situation develops (e.g., anaphylaxis) and immediate drug therapy is warranted (e.g., epinephrine).
The vastus lateralis muscle is capable of receiving 8 to 15 ml of injected drug (in adults) without distortion or dissection of muscle fibers. This represents the largest available reservoir for IM drugs in the adult body.
The deltoid muscle is easily accessible in the upper third of the arm. The injection is given between the upper and lower portions of the deltoid muscle (Figure 10-5), thereby avoiding the radial nerve.
The boundaries of the deltoid region form a rectangle. The superior border is formed by the lower edge of the acromion (the outward extension of the spine of the scapula). The inferior boundary lies opposite the axilla or armpit. The side boundaries are two lines drawn parallel to the arm, about one third to two thirds of the way around the lateral aspect of the upper arm.
Advantages of the deltoid region include easy access in most patients. It is important that the patient not be permitted to simply roll up the shirt sleeve to expose the injection site because if the sleeve is tight, it may not permit visualization of the entire site, in which case the injection might be administered inferior to the desired area and in too close proximity to the radial nerve. The patient should be required to remove the shirt or blouse to expose the entire injection site. A female assistant must be with the dentist (male or female) if the patient is female. Another positive factor in the deltoid region is more rapid absorption of the injected drug into the cardiovascular system than is seen with any of the other IM injection sites. Perfusion is 20% greater in the deltoid region than in the gluteal region.14 The deltoid region is not recommended for use in the infant or child who has not yet begun to walk.11
The degree of disrobing required to visualize the injection site is not usually of significance in the deltoid region, making this the most easily used IM injection site in dentistry. This site may be used with the patient lying down, sitting, or standing.
Probably the only negative feature of this site, other than the anatomy, is its lack of size; it is able to accommodate only up to 4 ml of solution (adult). However, this is not of significance in dentistry because it is rare to ever administer more than 3 ml intramuscularly. Giovannitti and Trapp18 suggest the deltoid muscle as the preferred site for IM sedation in the dental environment.
Selection of the site for IM injection in dentistry is predicated on several factors, including the size (age) of the patient, degree of patient cooperation, and volume of solution to be injected. In the younger (smaller) pediatric patient, the preferred site for IM injection is the vastus lateralis, whereas in older children the vastus lateralis and the deltoid regions are recommended. In the adult, the preferred sites for IM injection are the deltoid region, vastus lateralis, and both gluteal injection sites. Table 10-1 compares the four IM injection sites.
There is a very real concern for self-inflicted puncture injuries among health care professionals with possible infection with either human immunodeficiency virus (HIV) or hepatitis.19–22 Syringes and other devices (e.g., the “sharps” container) have been developed to permit IM drug administration with a minimal risk of needlestick injury.23–25 These “safe syringes” prevent accidental needlestick following drug administration through a self-locking sheath that covers the exposed (and now contaminated) needle.
The appropriate injection site for the IM injection must be selected. After disrobing the patient, if necessary, the dentist must carefully palpate the site on every patient to determine the precise anatomic landmarks. Visual examination alone should never be relied on to determine landmarks. From the point of view of propriety (and medicolegally), it is important that the dentist have another staff member present in the treatment room during the injection, especially if the patient is of the opposite sex from the dentist. The following are step-by-step instructions for the administration of an IM injection11,15,26:
The needle itself is capable of producing injury to structures through which it passes. Nerve damage, consisting of paralysis (usually of the sciatic nerve in gluteal injection), hyperesthesia, or paresthesia, has been reported after IM injection. In addition, inadvertent IV and intraarterial (IA) drug administration have occurred, as well as air embolism, periostitis, and hematoma. Many of these complications have potentially serious consequences and, of course, steps should be taken to prevent their occurrence. Knowledge of anatomy and proper injection technique will minimize these complications.
The drugs that are administered intramuscularly are, in some cases, capable of producing injury to the tissues into which they are deposited. Injuries such as abscess, cyst and scar formation, and necrosis and sloughing of skin at the injection site may occur. Although these are potential complications with all drugs, there are a few drugs that, because of their pH or viscosity, are more apt to produce these problems. These drugs include diazepam and hydroxyzine. Improper injection technique, specifically when the drug has not been injected deep into the muscle or when the tissue is kept taut following the injection of the drug with leakage of the drug into the subcutaneous tissues as the needle is withdrawn, is a common cause of this problem.
Nerve injury of any type is managed conservatively. In many cases, the injury may not be noted by the patient for several days following the IM injection or, in the case of a younger patient or a patient with a disability, possibly for several months, thus emphasizing the importance of precise recordkeeping. The site of injection should always be recorded when an IM drug is given. When injury is detected, the patient should return to the office so that the nature and extent of the injury may be noted on the chart. Unless the injury is severe, the management of choice for most nerve injury is “tincture of time.” Most minor traumatic nerve injuries resolve with time. In most instances, normal function returns within 6 months. The patient should be advised of this time factor at the onset. A few cases of nerve injury do not resolve completely within 6 months and require additional time (an unknown duration) or may never return completely to normal function. Periodic examination of the patient during this time span (e.g., once every month) is recommended to keep the dentist informed of any progress and to keep the patient aware of the dentist’s concern.
Discomfort secondary to the injury should be manageable with milder analgesics, such as aspirin, acetaminophen, or another nonsteroidal antiinflammatory drug (NSAID). If more potent analgesics are required, consultation with a physician is recommended because this might indicate a greater degree of injury.
If the injury appears more severe at the onset, the patient should be referred to a physician, preferably a neurologist, for examination. Medical management usually is consistent with that described. Referral to a physician should also be given serious consideration if the patient appears to be dissatisfied with the progress of his or her recovery or with the management of the injury by the “dental doctor.” Before referral of the patient to the physician, a telephone call from the dentist explaining the circumstances surrounding the case is appropriate.
Although legal action following nerve injury does occur, the number of such cases is extremely small. A patient who is satisfied with their treatment is less likely to initiate a legal action than the patient who believes that the care rendered is below the usual standard.
Inadvertent IV or IA drug administration ought to never occur. Proper IM technique recommends aspiration before injection of the drug. The presence of blood in the syringe indicates a positive aspiration. The dentist should remove the syringe from the injection site, apply pressure to the site to prevent hematoma, and reinject the patient at a different location.
Because the drugs administered for sedation are CNS depressants, clinical signs and symptoms attending this complication (accidental IV or IA administration) are related to the degree of CNS depression that develops. This may range from a slightly oversedated patient—one who is conscious but sedated to a degree beyond which the dentist feels comfortable—to the patient who may be unconscious but breathing (requiring airway management), to the unconscious patient whose breathing is quite depressed or who may be apneic. This latter patient requires “rescue”: airway management with controlled ventilation. The pharmacology and the cerebral blood level of the drug(s) injected determine the severity of the reaction that develops. Some antianxiety drugs, such as benzodiazepines (e.g., midazolam) and hydroxyzine, although capable of producing significant CNS depression, are less likely to than barbiturates and opioids.
Management (rescue) of an oversedated patient consists primarily of airway maintenance (A, airway) and, when necessary, assisted or controlled ventilation (B, breathing). In addition, some drugs, such as the opioids and benzodiazepines, have pharmacologic antagonists that may be administered in these circumstances. Their use and a more detailed discussion of the management of the oversedated patient are found in Chapters 27 and 34.
Air embolisms have been reported after IM drug administration. With proper technique in loading a drug into a syringe, there ought not to be any air remaining in its barrel. In addition, avoidance of inadvertent intravascular injection (see previous discussion) will prevent this occurrence.
Periostitis is an inflammation of the periosteum. If acute, it may be associated with severe pain and suppuration. It occurs frequently secondary to infection. The condition usually becomes chronic in nature and is characterized by tenderness and swelling of the tissues overlying the bone. It may also be produced by the inadvertent striking of the needle against the periosteum during insertion. Proper technique involves grasping the tissue being injected between the fingers, pulling it away from the bone, and inserting the needle to the proper depth (varying from patient to patient and from site to site). This technique minimizes the development of periostitis.
If the patient complains of soreness, tenderness, and swelling at the site of an IM injection 2 days or more following injection, the complaint should be evaluated by bringing the patient to the office, examining the area, and, if necessary, seeking a medical consultation. Management of milder degrees of periostitis involves “tincture of time” and the maintenance of good relations with the patient. If signs of suppuration and swelling appear, antibiotics are indicated (usually penicillin). Medical consultation should be sought in this situation.
Hematoma is, by definition, a tumor consisting of effused blood. It develops following puncture of a blood vessel, either an artery or a vein. Clinically a small but gradually enlarging swelling, bluish in color, will be observed at the site of needle insertion, either during injection or, more commonly, after withdrawal of the needle from the tissues. Management consists of pressure applied directly to the site of bleeding for a minimum of 2 to 5 minutes. If the site subsequently becomes sore, heat can be applied to it (but not less than 4 hours after the bleeding ceases) and mild analgesics administered. The effused blood is gradually resorbed into the cardiovascular system, a process requiring 7 to 10 days. Heat should not be applied to the site of a hematoma within the first few hours because heat produces vasodilation, which may restart the bleeding.
An abscess may occur after IM injection if either the needle or the solution injected was contaminated. Management consists of antibiotics (penicillin) and immediate medical consultation. Prevention consists of sterile technique in handling both drugs and equipment.
Cyst formation, scarring, and necrosis and sloughing of tissues may also occur. Although several factors may be responsible for these, many are produced by the tissues’ reaction to the injected drug. Drugs that are irritating to the tissues are more commonly involved in these complications. Superficial injection of drugs is another possible cause of this problem. Management should consist of referral to a physician, preferably a dermatologist. Complications of IM injections are listed in Box 10-3.
The factors that influence the way in which a drug acts in a given patient were discussed in Chapters 3 and 7. With IM administration of CNS depressants, the influence of these various factors becomes quite important. How can the informed clinician safely determine the appropriate IM dose of the drug or drugs that are to be administered to a patient for intraoperative sedation?
Most IM drugs have their dosages determined, in large part, by the body weight of the patient. Although this is far from an absolute guarantee of proper dosage, in most cases, a therapeutically effective result will occur. Other factors that must be considered in determining dosage include the degree of anxiety, the level of sedation desired, the patient’s age and health status, prior response of the patient to CNS-depressant drugs, and the education and experience of the drug’s administrator.
For the adult patient, dosages for the drugs discussed are based primarily on body weight, expressed in milligrams per kilogram (mg/kg) or milligrams per pound (mg/lb). From this calculated dose, the dentist will decrease or increase the actual dosage administered as determined from the other factors mentioned. For example, a patient weighing 70 kg is to receive a drug, the recommended dose of which is 1.0 mg/kg. The calculated dose of this drug for the patient is therefore 70 mg. If the patient were a healthy individual (American Society of Anesthesiologists [ASA] 1), this dose would be appropriate; however, if this patient is older, has a history of cardiovascular or other serious systemic disorders, or has a history of overreaction to average drug dosages (is a hyperresponder), a smaller dose (e.g., 50 mg) might be administered. The level to which the drug dosage is decreased is left to the clinical judgment of the dentist administering it. Conversely an ASA 1 patient demonstrating high levels of anxiety, with a history of hyporesponding to CNS-depressant drugs, might be administered a dose somewhat greater than that determined strictly by body weight.
In the pediatric patient, the same factors must be considered in determining drug dosage. The patient’s age is often considered in determining the dosage of a drug. For example, for a given drug, the dose for a 3-year-old patient may be 12.5 mg, whereas the dose for a 4-year-old is 25 mg. Dosages based solely on the patient’s age are apt to lead to inaccuracies because patients of the same age will vary considerably in physical stature and body weight. The patient’s age should not be the primary factor by which the dose of a drug is determined.
Several rules have been used for years in the determination of pediatric drug dosages. Clark’s rule takes the weight of the child in pounds and divides it by 150 (the weight of the average adult in pounds). The resultant fraction is multiplied by the adult dosage of the drug.
A factor that has proven even more accurate in determining effective pediatric dosages is the body surface area of the patient. Table 10-2 permits a determination of the approximate surface area of the patient. The pediatric dosage is determined as a percentage of the usual adult dosage, based on the average adult surface area of 1.73 m2.
Most of the drugs discussed in this chapter have their dosages presented on a milligram per kilogram or pound of body weight basis. Although not the most accurate method available, this remains the most frequently employed method of determining IM drug dosage. The reader may employ the surface area method of determining pediatric dosages for any drug listed in this book by simply referring to Table 10-2.
Dosages based on body weight (e.g., 1 mg/kg or 0.5 mg/lb) are determined by the middle of the “bell-shaped” curve (see Figure 7-1). Approximately 70% of patients respond appropriately to this dose, with 15% undersedated. Unfortunately, another 15% respond in an exaggerated manner—oversedation.
The degree of education and experience of the drug administrator has a significant bearing on the level of CNS depression to which the patient may safely be taken, which will obviously influence the dosage of drug administered. Doctors who have completed residency training in anesthesiology will be better able to administer larger doses of drugs to patients in a safe manner than those who have completed a short postgraduate program (e.g., continuing education). All dental personnel involved in patient management should be adept in monitoring vital signs and in recognizing and managing life-threatening emergencies, including the ability to rescue the patient from an unintended lapse into a deeper level of CNS depression (e.g., perform basic life support).
A myriad of drugs are available for the management of anxiety via IM administration. The level of sedation may vary from lighter levels (minimal to moderate sedation) to levels approaching unconsciousness (deep sedation). Although certain drugs are more apt to produce more profound sedation than others, any of the following drugs listed can produce overly deep sedation. When IM drug dosage is determined, it must always be remembered that the administrator cannot control the drug’s action, and that titration is not possible via this route. Care and prudence must be exercised whenever IM drugs are administered to all patients, but especially to pediatric, geriatric, or medically compromised patients. Box 10-4 lists drugs that are commonly given via IM administration in dentistry. As will be noted with specific drugs, different levels of training are recommended for their safe use. In some situations, the dentist should have received training in general anesthesia and be capable of managing the unconscious airway before ever considering the use of the drug in question.
Frequently Used Drugs Via Intramuscular Administration for Sedation
In this group of drugs—antianxiety and sedative-hypnotics—I have included the benzodiazepines and histamine blockers, drugs commonly used for minimal to moderate levels of sedation when given as solo agents. However, it is not uncommon to combine one of the drugs in this category with an opioid analgesic to provide deeper levels of sedation. When this is done, it is necessary for the dentist and all staff members to have been thoroughly trained in general anesthesia and patient monitoring. The barbiturates have been excluded from the discussion of IM drugs in this fifth edition. Negatives associated with their IM administration outweigh, in my mind, any benefit gained from their administration. Primary among these is the degree of respiratory depression seen at therapeutic levels of barbiturates. The reader is referred to previous editions of this textbook for discussion of IM barbiturates.
Chlordiazepoxide (Librium) is one of a number of benzodiazepines available for parenteral administration. Patients receiving chlordiazepoxide parenterally should be cautioned against the operation of a car or other potentially hazardous machinery for the remainder of the day.
Because the parenteral preparation of chlordiazepoxide is not very stable, it is prepared for use immediately before its administration. Two milliliters of an IM diluent (provided with the drug) is injected into the ampule of chlordiazepoxide powder (100 mg). The solution is agitated slowly and gently until the powder is completely dissolved. This provides a solution of chlordiazepoxide at 50 mg/ml.
Chlordiazepoxide should be administered deep into muscle to minimize discomfort and to optimize absorption. It is recommended that the drug be deposited slowly into the upper outer quadrant of the gluteus muscle.29 Any unused drug should be discarded. Following parenteral administration deep into muscle, the onset of action will be approximately 15 minutes. Maximal clinical effect arises 30 minutes following injection, with a gradual decrease in clinical action over the next 3 to 5 hours.30
Because of the necessity to prepare chlordiazepoxide immediately before injection, it is rarely employed in dentistry for IM sedation. Other benzodiazepines are more readily available for parenteral administration.
The usual adult dose for preoperative sedation is 50 to 100 mg 1 hour before treatment. The usual dose for elderly or debilitated patients is 25 to 50 mg 1 hour before treatment. Chlordiazepoxide injectable is not recommended in patients younger than 12 years.
Librium (Roche): 5-ml dry-filled ampule containing 100 mg chlordiazepoxide hydrochloride in dry crystalline form; 2-ml ampule of Special Intramuscular Diluent containing 1.5% benzyl alcohol, 4% polysorbate 80, 20% propylene glycol, 1.6% maleic acid, and sodium hydroxide (to adjust pH to 3.0). When prepared for injection, the concentration of the chlordiazepoxide is 50 mg/ml. Chlordiazepoxide is classified as a Schedule IV drug.
Before the introduction of midazolam, diazepam (Valium) was commonly administered via the IM route in preoperative anxiety control in the hospital setting. It may also be given in dentistry via this route, but because of the availability of the IV route and the advantages of IM midazolam, diazepam is only rarely used IM in dentistry.
Another reason for the infrequent use of diazepam IM was the results of early studies on the absorption of diazepam from IM injection sites. Diazepam injectable is an extremely lipophilic drug, and early studies on absorption of IM diazepam were conflicting.31–34 Peak plasma levels were noted 60 minutes after oral dosing, whereas IM dosing required 90 minutes.34 Absorption of diazepam from IM injection sites may be slow or incomplete or both because of its lipophilic nature. However, a more recent report indicates that IM diazepam absorption appears to be more rapid when the drug is injected into the deltoid rather than the gluteal or vastus lateralis muscle groups.35 The most likely explanation is the higher blood flow per gram of tissue in the deltoid muscle group.33 In the gluteal area, the depth of injection may be a factor in the completeness of absorption of diazepam. Given equal doses of diazepam via the oral and IM routes, the oral dose will be absorbed more completely than the IM dose, and in many cases, the rate of onset will be shorter via the oral route than with the IM route.34 However, diazepam deposited deeply into muscle (preferably the deltoid) can produce satisfactory sedation in most patients.
Parenteral diazepam should be avoided in patients with known hypersensitivities to it or other benzodiazepines, in patients with acute narrow-angle glaucoma, and in patients with narrow-angle glaucoma unless they are receiving appropriate therapy.
When used in combination with other CNS depressants, particularly opioid analgesics, the dosage of the opioid should be decreased by approximately one third to minimize the occurrence of oversedation or of other more serious complications.
Diazepam should not be given during the first trimester of pregnancy because an increased risk of congenital malformations has been observed. Diazepam crosses the placental barrier, potentially producing depression of the fetus. Its use in pregnancy is not recommended.
Injectable diazepam doses should be decreased when patients are receiving other CNS depressants, such as barbiturates, phenothiazines, opioids, and alcohol. Elderly and debilitated patients usually require decreased doses of diazepam to achieve a desired clinical effect.
The usual adult dose for preoperative sedation is 10 mg 30 minutes to 1 hour before treatment. The preferred injection site for diazepam is the deltoid muscle. Regardless of the IM injection site, diazepam should be deposited deep into muscle to prevent discomfort and provide more reliable absorption. The dose for elderly or debilitated patients is 2 to 5 mg 30 minutes to 1 hour before treatment. The dose of parenteral diazepam for children should not exceed 0.25 mg/kg of body weight, administered deep into the gluteal or deltoid regions. For example, a child weighing 20 kg (44 lb) will receive a dose of 5 mg IM diazepam. Since the introduction of midazolam, the IM use of diazepam has greatly diminished.
Valium (Roche): 5 mg/ml in 2-ml ampules and 10-ml vials; 5 mg/ml in 2-ml preloaded syringes. Injectable diazepam also contains 40% propylene glycol, 10% ethyl alcohol, 5% sodium benzoate, benzoic acid, and 1.5% benzyl alcohol. Diazepam is classified as a Schedule IV drug.
Lorazepam (Ativan) is another benzodiazepine available for parenteral administration. Its action following parenteral administration is primarily that of sedation rather than anxiolysis. A potential benefit of IM lorazepam is that it frequently provides a degree of amnesia. This lack of recall is maximal within 2 hours of IM injection.
Because the agent is virtually insoluble in water, its onset of action may prove to be prolonged in some patients, although, as with diazepam, the onset of action will be about 15 minutes in most patients. Peak plasma levels of lorazepam are seen in 60 to 90 minutes.36 The duration of action of lorazepam following IM administration is approximately 6 to 8 hours. The major side effect is excessive sleepiness and a prolonged amnesic period.
Odugbesan and Magbagbeola37 recommend that the IV route be preferred to IM for administration of lorazepam, providing a somewhat more rapid onset of activity. Patients receiving lorazepam IM must not be permitted to leave the dental office unescorted and must be advised of the possibly enhanced CNS-depressant actions of other agents, such as opioids, alcohol, and barbiturates. Because of the prolonged duration of action of lorazepam, it is seldom used in the outpatient practice of dentistry.