| Contraceptive prototypes for
men use one of two mechanisms of action: some suppress sperm production, either through
hormonal or non-hormonal means; others inhibit the ability of sperm to fertilize the ovum,
usually by disrupting a key step necessary for conception. |
| Agent |
How it Works |
Research Status |
| Hormonal Suppression of Sperm Production |
| Gonadotropin hormone- releasing
hormone (GnRH) coupled with protein |
- Stimulates immune system to inactivate the body's natural GnRH, suppressing sperm
production
- Annual injection
|
Two-year safety trial of gonadotropin
hormone-releasing hormone (GnRH) combined with tetanus toxoid protein recently begun in 20
men. |
| 7-alpha
methyl-19-nortestosterone (MENT) |
- Suppresses sperm production
- Annual implant
|
Efficacy trials of MENT implant under way;
long-term toxicology testing not yet conducted. |
| Testosterone buciclate (TB) |
- Suppresses GnRH secretion and thus sperm production
- Three-month injection
|
TB injectable tested in a WHO-supported
study indicates stronger dosage necessary for reliable contraception. Trials of TB
injectable and progestogen may begin in 1998. |
| Testosterone undecanoate (TU) |
- Suppresses GnRH secretion and thus sperm production
- One or two-month injection
|
Studies among men under way in China of TU
injectable; studies of two-month TU injection with a progestogen planned. |
| Testosterone enanthate (TE) |
- Suppresses GnRH secretion and thus sperm production
- Weekly injection
|
Provided effective contraception in 98
percent of 399 men in a two-year WHO trial, but not considered desirable for general use
because weekly injections are required. |
| TE/progestogen combination |
- Suppresses GnRH secretion and thus sperm production
- Weekly injection of TE, daily progestogen pill
|
Combination of TE and progestogen achieved
initial contraception sooner than TE alone, but not considered desirable for general use
because weekly injections are required. |
| Non-hormonal Suppression of Sperm Production |
| Gossypol |
- Suppresses sperm production
- Daily pill
- Irreversible in some men
|
Recent pilot study of low-dose gossypol
pill indicates effective contraception without dangerous potassium depletion. Larger
efficacy study of 320 men planned. |
| Inhibition of Fertilizing Ability of Sperm |
| Nifedipine |
- May prevent sperm enzyme action needed for fertilization
- Daily pill
|
Research planned to find variations of this
drug that may specifically target sperm without producing systemic side effects. |
| Mifepristone (RU 486) |
- Makes sperm temporarily immotile
- Daily pill
|
Research is seeking chemically-similar
compounds that may target sperm without producing mifepristone's undesirable side effects. |
| Sperm surface protein |
- Antibodies attached to sperm block fertilization
- Vaccine
|
Immunization of male guinea pigs with sperm
surface protein has demonstrated reversible contraception. Other animal studies planned. |
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