Contraceptive injections, implants and patches

Progestogen injections are available as two types: Depo-Provera (medroxyprogesterone), which protects from pregnancy for 12 weeks, and Noristerat (norethisterone), which protects for 8 weeks. They act by inhibiting ovulation, thickening cervical mucus, inhibiting the progress of sperm and thinning the endometrium.

A progestogen implant is a small flexible rod placed under the skin in the upper left arm. It works for up to 3 years. It contains etonorgestrel (Implanon). Some medicines render an implant less effective; these include drugs to treat HIV, epilepsy and tuberculosis, and St John’s wort.

Contraceptive patches (Evra) provide progestogens and oestrogens, and work for about 1 week, so new patches are used each week for 3 weeks, followed by a week’s break – just like the OCP.

Dental aspects of contraception

OCPs can interact with anticoagulants to disturb anticoagulant control and can impair the effect of tricyclic antidepressants. The significance of drug interactions for dental antibiotics with the OCP is probably low.

The predisposition to thromboembolic disease and hypertension theoretically necessitates precautions for operations under general anaesthesia (GA). However, if the patient is otherwise well, GA – in hospital of course – is not contraindicated. Despite the risk of thromboembolism, the disadvantages of discontinuing OCPs before GA outweigh any advantages.

OCPs may worsen gingivitis and possibly periodontitis and may increase the risk of dry sockets; jaw radio-opacities or altered trabecular patterns may appear.

Condoms

Male and female latex rubber condoms are available; they are inexpensive, have a high success rate approaching 100%, have virtually no side-effects and also protect against SSIs.

Other contraception that is more than 90% effective

Unreliable Forms of Contraception

Sexually Shared Infections Seen Worldwide

Sexually shared infections (SSIs), or sexually transmitted diseases (STDs) or infections (STIs), include bacterial, viral and fungal infections, and infestations (Table 32.4); they were formerly termed venereal diseases (VDs). Non-specific urethritis (NSU) and Chlamydia are probably the most common. There can be infection with more than one SSI, and SSIs generally increase the liability to transmission of viruses such as HIV, especially if there is mucosal or cutaneous ulceration. The group of the most common serious SSIs has been given the acronym SHAG (syphilis, herpes, anogenital warts and gonorrhoea).

Young people (age 16–24 years) now account for half of all SSI cases, and the incidence of virtually all of these infections is increasing. In the UK in 2008, nearly half a million people attended clinics for SSIs. Sexually promiscuous people can be the source of transmission to literally hundreds of others (Fig. 32.1). The risk of infection is highest in sex workers.

Prevention

SSIs are passed from person to person by direct contact, mainly via the external genitals, vagina, anus or rectum, or on the lips and in the mouth. Transmission of the microorganism occurs during vaginal, anal or oral sex. Pregnant women can sometimes pass infection to the fetus.

Oral, anal, vaginal or penile ulcers or other lesions make it easier to transmit and acquire SSIs. However, because SSI lesions can be hidden in the vagina or anus, under the foreskin or in the mouth, it may not be obvious that a sex partner is infected. Unless a person knows that their sex partners have been tested and treated, they may be at risk of reinfection from an untreated sex partner.

Since SSIs are passed from person to person through unsafe sexual practices, the risk of infection can be reduced by avoiding casual and unprotected sexual intercourse via:

The surest way to avoid transmission of SSIs is to abstain from sexual intercourse, or to be in a long-term mutually monogamous relationship with an uninfected partner who remains so. A man should always use a condom during sexual intercourse, each time, from start to finish, and a woman should make sure that her partner uses one. A woman can also protect herself from SSIs by using a female condom. Dental dams have been advocated for protection against transmission of SSIs during cunnilingus or oroanal contacts.

Although any person can be at risk of contracting SSIs, members of certain groups can be at especially high risk; some sell sex to underpin their drug habits (Box 32.1 and Fig. 32.2). Close contact is essential to SSI transmission; they cannot be spread through social contact or via toilet seats, doorknobs, swimming pools, hot tubs, bathtubs, shared clothing or eating utensils.