Contracepção espermicida

What is a spermicide?

Spermicidal agents are defined as drugs that have the ability to immobilise or kill the sperm upon contact. An ideal spermicide should immediately and irreversibly produce immobilisation of the sperm, non-irritating to the vaginal and penile mucosa, not have adverse effects on the developing fetus, free from long-term topical and systemic toxicity and should not be systemically absorbed.¹

Available spermicidal contraceptives

Nonoxinol-9 is the most commonly used spermicidal agent and is the active component in the only prescribable spermicide available in the UK. Spermicidal contraceptives are useful additional safeguards but have low contraceptive efficacy if used alone.²

High frequency use of the spermicide nonoxinol ‘9’ has been associated with genital lesions, which may increase the risk of acquiring these infections.³

Spermicidal contraceptives are available as:

• Aerosol foam.

• Jelly.

• Creme.

• Film.

• Sponge.

• Pessary.

In the UK, however, the only currently prescribable form is Gygel® contraceptive gel. ³

When should spermicidal contraception be used? (Indication)^{3 4}

Spermicidal contraceptives are suitable for use with barrier methods, such as diaphragms or caps, but are not recommended for use with condoms, as there is no evidence of any additional protection compared with non-spermicidal lubricants.

Spermicidal contraceptives are also not suitable for use in those with or at high risk of infecções sexualmente transmissíveis (including HIV).

How well does spermicidal contraception work? (Efficacy)²

Because of poor trial quality, how well spermicides work in preventing pregnancy is unclear.⁵ However, it is known that gel with the smallest amount of nonoxinol-9 is less effective in preventing pregnancy than products containing more of the same ingredient.

Overall efficacy is poor in comparison to other contraceptive options, with a Cochrane review showing pregnancy rates within six months in trials ranging from 14-22%. Trials had a high discontinuation rate, or participants were lost to follow-up; the conclusion was that interpretation of the results was limited.

Cochrane reviews have found the contraceptive diaphragm with spermicide to be more effective than use with a contraceptive sponge.⁶

Modo de ação¹

Diaphragms and caps are barrier methods of contraception and therefore prevent fertilisation. They cover the cervix, acting as a barrier blocking the cervix as well as providing a reservoir for spermicide. Spermicide should be reapplied if the cap or diaphragm has been in situ for longer than three hours. Spermicide works by:

• Altering the integrity of the sperm cell membrane.

• Altering the vaginal pH, causing a hostile environment for sperm.

The advantages of a spermicide include additional lubrication and possibly improved efficacy.

The disadvantages are:

• It must be inserted prior to intercourse and reapplied if intercourse takes place more than three hours later.

• Some may find it messy, or smelly, or that it has an unpleasant taste.

• It may cause irritation and subsequent increased risk of transmission of infections.

• Occasionally it may induce an allergic reaction.