Amphetamine & Sex

1 Introduction

1.1 Amphetamine was widely prescribed until the mid 1960s as a stimulant and appetite-suppressant, until the dependence-potential of amphetamine (and other stimulants) led to a falling out of favour among the medical profession. Amphetamine, although a controlled drugs, is still prescribable for certain conditions (e.g. narcolepsy)[i], and appears in Schedule 2 of the Misuse of Drug Regulations 1985, meaning that it can be prescribed for medical treatment subject to proper monitoring and reporting criteria.

1.2 Amphetamine is a powerful central nervous system stimulant drug, used recreationally for the euphoriant effects, as well as "functionally" to ward off fatigue and increase energy and capacity for physical activity. The effects of amphetamine are similar to those of cocaine, both affecting the same neural systems, amphetamine stimulates catecholamine release, and cocaine reduces reuptake - expressed simply, if the level of alertness were to be represented by the water level in a bath, amphetamine would act by turning on the taps, whereas cocaine would act by putting in the plug.

1.3 The effects of amphetamine have been studied for over a century, although since it became a controlled drug in most countries of the world, opportunities for research on the effects on humans have been limited.

2 Human Studies

2.1 There have been several studies of heterosexual and homosexual behaviour, including high HIV-risk practices, among chronic amphetamine users, with conflicting results. In a clinical review, Miczek & Tidey[ii] found "Most often... amphetamines disrupt social, sexual, maternal, and aggressive behavior patterns in a dose-dependent manner; neither tolerance nor sensitization appears to develop to these disruptive effects".

2.2 Our own IDMU surveys have found enhancement of sex by amphetamine to be a commonly reported "best drug experience". However these results have yet to be analysed in detail and, as open ended questions, provide qualitative rather than quantitative data, and are of the nature of anecdotal reports.

2.3 In a study of 200 injecting drug users in Sweden, Kall[iii] reported "Amphetamine injectors, who constitute the majority of drug injectors in Stockholm, reported a higher frequency of intercourse on drugs with regular partners than did the heroin users", from the same study, Kall & Nilsonne[iv] found "Sexual activity was reported as the preferred activity on amphetamine by 51% of the male and 20% of the female amphetamine injectors", and concluded "preferring sex on amphetamine may be viewed as a marker of high risk behaviour, both sexually and with needles, for HIV among male but not among female amphetamine injectors". Kall"s pilot study[v] had earlier found "Of the 29 men, 27 had experience of sexual activity while using amphetamine. Of these, 23 reported that they became more sexually excited when on amphetamine, 21 reported intensified orgasms, and 23 reported that the drug prolonged intercourse. All 29 men had been sexually active, but only 6 of the amphetamine users had had more than 10 partners during the last 3 years. Condom use was very low; it was reported by only 3 men during their last intercourse with a causal partner."

2.4 In a study of female intravenous drug users in the UK, Klee[vi] reported "Marked differences were observed in sexual behaviour, amphetamine injectors reporting greater interest in sex and greater frequency of intercourse. However, more of them perceived their personal risk to infection through unprotected sex as negligible." In Hawaii, Laidler & Morgan[vii] quote one woman: "God what sex we had, Go! Go! Go!... It gave me more courage, it made me braver" In Switzerland, Muller[viii] reported "The influence of drug abuse on sexuality is usually felt to be negative (decline in libidinal energy, impotence), and often brings about a decrease in sexual contacts. This is equally true of both opiates and stimulants (cocaine, amphetamine). Promiscuous behaviour is rare as such and does not occur with any greater frequency than among the average population". In Australia, Hando & Hall[ix] found "Sexual risk-taking was not related to needle-sharing or amphetamine use."

2.5 In the USA studying methamphetamine users, Morgan & Beck[x] found a range of opinions and experiences, suggesting sexual energy and released inhibitions common among gay men "I was running around trying to have sex with everybody", heterosexual users reported sexual pleasure from the drug rush itself "when a woman does a bit of crank she comes, climaxes", others reported extremely heightened and prolonged sexual activity á a 30 year old woman was quoted "I had no idea it was two weeks! It was a lot of sex, listen to the stereo, more sex, do dope, talk, more sex, for two weeks. I could a went for more, my kids missed me, days turned into nights and nights into days" Worm & Steentoft[xi] studied drug-positive arrestees in Denmark, and found "In 194 of the amphetamine-positive cases where relevant information was available, 56% were cases of violation of the traffic laws, 17% were cases of violence, 3% were cases of sexual offence and 9% were cases of robbery." Greaves[xii] reported "sexual disturbances" among chronic amphetamine users.

2.6 In Thailand, Melbye et al[xiii] reported "Several STDs were associated with amphetamine use: gonorrhea (OR 2.3) and genital warts (OR 2.4), and any STD (OR 1.9). In multivariate analysis, use of heroin (OR 3.1), soft drugs (OR 4.9), and a history of gonorrhea (OR 2.0) were independently associated with amphetamine use in northern Thai men." Von et al[xiv] reported clients using methamphetamine "to enhance sexual experience". In a study of amphetamine use among youths infected with HIV, Rotheram-Borus et al found "Compared with those who have never used (never-users), users... had more sexual partners and more sexual encounters." In a comparative study of heroin and methamphetamine injectors, Zule et al[xv] noted "Of methamphetamine users, 71% had more than one sex partner, compared to 39% of heroin users."

2.7 Gay Men: In a study of gay and bisexual US males, McNall & Remafedi[xvi] noted "Significant univariate associations were found between drug use before or during sex and unprotected anal intercourse for the following substances: alcohol, marijuana, cocaine, amphetamines, barbiturates, heroin, LSD, volatile nitrites, tranquilizers, and methaqualone. In multivariate analyses, however, only cocaine use predicted failure to use condoms during anal intercourse." Stone et al[xvii] found heavy amphetamine and alcohol use was associated with higher rates of condom use, and condom failure, in insertive and receptive anal sex. Semple et al[xviii] noted "Previous research has documented an association between methamphetamine (meth) use and high-risk sex among HIV- men who have sex with men", finding that "meth use was associated with high rates of anal sex, low rates of condom use, multiple sex partners, sexual marathons, and anonymous sex. Personal motivations associated with meth use included: sexual enhancement". Shoptaw et al[xix] noted "Methamphetamine, a drug used at alarming rates among gay/bisexual males in the West, is often combined with sexual activities, thereby increasing HIV-related risks in an already high-risk group". Halkitis et al[xx] reported "Methamphetamine is often used by gay men to initiate, enhance, and prolong sexual encounters. Use of the drug is, therefore, associated with particular environments where sexual contact among gay men is promoted, such as sex clubs and large "circuit" parties. Research with gay and bisexual men indicates that methamphetamine use is strongly associated with risky sexual behaviors that may transmit HIV. This relationship, coupled with emerging evidence that methamphetamine use is on the rise among gay men, suggests that the drug could exacerbate the HIV/AIDS epidemic among this community."

2.8 Other stimulant drugs: McBride et al[xxi] found crack cocaine use to be associated with a significantly higher number of sexual partners. In Ethiopia, Taffa et al[xxii] found "alcohol use and khat (amphetamine-like substance) consumption predicted the likelihood of engagement in sexual activity." In a reviewarticle Schiorring[xxiii] noted that stimulant drugs "prolonged sexual intercourse without ejaculation"

3 Animal Studies

3.1 In rats with cerebral cortex lesions, Agmo et al[xxiv] found amphetamine reduced mounting latencies, but had no effect in healthy (intact) animals. They earlier noted[xxv] that "(inexperienced) male (rats) are critically dependent on stimuli from the female in order to initiate sexual behavior, and catecholamines are known to modulate interactions with environmental stimuli. It was found that D-amphetamine, 0.5 and 1 mg/kg... reduced mount and intromission latencies.". In female rats, Nance et al[xxvi] found an increased level of lordosis (sexual display/behaviour) in rats with septal lesions, but found "amphetamine was found to reduce the high levels of lordosis behavior of septal lesioned female rats to control levels". Nojcar et al[xxvii] noted "Appetitive behavior for drug and sexual reward is enhanced in animals with a history of amphetamine-experience."

3.2 Becker et al[xxviii] found significant sex differences in the behavioural responses of male and female rats to amphetamine, and in female rats, Diaz-Veliz et al[xxix] found differences in behavioural responses to amphetamine at different times within the oestrus cycle, with reduced effect in the dioestrus (post-ovulation ) phase.

3.3 In hamsters, Bradley & Meisel[xxx] found "sexually experienced animals responded sooner to amphetamine than did sexually naive animals. These data indicate that female sexual behavior can activate neurons in the nucleus accumbens and that sexual experience can cross-sensitize neuronal responses to amphetamine." Studying the effect of amphetamine withdrawal on sexual behaviour of male rats, Barr et al found[xxxi] "Withdrawal from the drug was associated with decrements in several motivational components of sexual behavior, including decreased anticipatory locomotor and increased postejaculatory intervals, while consummatory measures remained largely unaffected. This pattern of sexual deficits resembles those seen in human depressive disorders"

3.4 Fiorino & Phillips[xxxii] reported "After a 3-week post-drug period, d-amphetamine-treated rats exhibited facilitated sexual behavior, as indicated by shorter latencies to mount and intromit, and a greater percentage of rats copulating. These rats also exhibited a general increase in the amount of copulation. Furthermore, sensitized rats displayed a facilitated acquisition of sexual behavior (i.e. mount and intromission latency <300 s for 3 consecutive days). After repeated sexual experience, rats pre-treated with d-amphetamine also showed an augmented increase in level changes made in anticipation of the presentation of a receptive female. Finally, enhanced sexual behavior was independent of the environment in which repeated administration of d-amphetamine occurred, indicating that facilitation was not a consequence of conditioned associations between drug and test environment." Carter et al[xxxiii] reported "amphetamine (2.5 mg/kg) did not potentiate lordosis in ovariectomized hamsters after either 2 or 6 days of EB priming... Lordosis in the female rat is more readily elicited both by drugs and estrogen. It is proposed with regard to female sexual behavior that species differences in estrogen sensitivity may underlie apparent differences in drug sensitivity", having earlier noted[xxxiv] "Amphetamine did not interrupt either male or female sexual behavior". Dallo et al[xxxv] found "Amphetamine (2 mg/kg) (exerts a moderate aphrodisiac effect in sexually sluggish rats) with a... rapid onset and offset of the effect." Saito et al[xxxvi] concluded "methamphetamine inhibits the intromitting and ejaculating behavior in male rats"

3.5 In male macaque monkeys, Bellarosa et al[xxxvii] found "d-Amphetamine increased vocalization, self-grooming, playing (low doses), social grooming (low doses), and aggression (low doses). At higher doses most forms of social interaction (playing, social grooming) were greatly decreased. Presenting behavior was increased by all doses under both treatment conditions. Mounting was increased to a much lesser extent and only after concurrent dosing. The increased presenting and mounting may be a result of sexual stimulation or perhaps more likely, an indication of increased submissive behavior directed toward more dominant animals."

 

4 Summary- Amphetamine and Sexuality

4.1 There are a large number of human studies finding an association between chronic or heavy amphetamine use and increased sexual activity and/or high-risk sexual behaviours, and use of amphetamines is considered a high-risk factor for HIV infection. However none of these studies have resolved the issue of whether amphetamine use causes such behaviour, or whether such behaviour and amphetamine use are both symptoms of an underlying risk-taking or sensation-seeking personality.

4.2 Animal studies provide conflicting and confusing evidence, some finding amphetamine to "normalise" sexual behaviour in lesioned animals, others to find a reduction, and others an increase in sexual behaviour following administration of or pre-treatment with amphetamine.

4.3 There is some evidence from animal studies that sensitivity of females to the effects of amphetamine may vary over the menstrual cycle, with enhanced sensitivity in the pre-ovulatory period and reduced sensitivity in the post-ovulatory period.

4.4 The evidence suggests that chronic amphetamine users may be more likely to engage in sexual activity than users of other drugs (e.g. opiates). Although the effects of amphetamine on the libido of a na•ve user are unclear, the evidence suggests that enhanced energy, stamina and appreciation of sex are commonly sought by users of amphetamine.