Methamphetamine (N-methyl-1-phenyl-propan-2-amine), also known as meth, crystal, chalk, and ice, is a psychoactive substance that stimulates the central nervous system when ingested. It belongs to a drug class called “psychomotor stimulants,” as it produces increased energy and attention.¹ It is infrequently prescribed by clinicians to treat the symptoms of attention deficit hyperactivity disorder (ADHD), but is known to be used recreationally.¹ Methamphetamine is a schedule II-controlled substance, meaning that its unprescribed use, trafficking, and distribution is illegal in the United States. Because this compound is not naturally produced by the body, it is considered a “drug,” and has a significant effect on the body when administered in small doses^.2  It can be ingested in the form of a pill, smoked in a pipe, or injected with a needle.¹  When administered intravenously, typically using a needle to enter the veins, the drug has the quickest onset and shortest duration of action.¹ This is because the drug is immediately delivered to the bloodstream and reaches the brain with fewer barriers. A drug must have certain properties, such as being molecularly small, to be able to cross the brain’s protective lining and take action in the brain’s circuitry.²

Methamphetamine has a high addictive liability because it produces instant euphoria, causing feelings of joy and elation, that lasts for only a short period of time.³ This can lead a user to take the drug many times in order to maintain this high. When used repeatedly, the user will gradually build a tolerance to the drug effect, meaning that a higher dosage is required to experience the original effect or feeling. Tolerance occurs as the body makes adjustments to compensate for bodily changes caused by drug use and is sometimes irreversible.⁴

Effects on the Brain

Methamphetamine stimulates the release of dopamine. Dopamine is a chemical produced naturally in the brain.⁵ Dopamine normally affects pleasure, movement, attention, and learning. It also plays a role in motivation and reward and is implicated in many compounds that are subject to substance use disorders.² The euphoric effect experienced after methamphetamine ingestion will diminish with frequent use, so a user will have to incrementally increase their dosage in subsequent drug uses to feel the same magnitude of euphoria.⁴ This property, accompanied by a compensatory downregulation of the user’s endogenous dopamine release, reinforces continuous drug use. The high experienced when the drug reaches the brain occurs because methamphetamine stimulates a large increase in dopamine release in reward regions of the brain, causing the euphoric feeling and a motivational association with drug taking.¹ It does this through two mechanisms of action. The first involves disrupting the gradient that allows for intracellular storage of dopamine, causing neurons to release excesses of dopamine. The other involves blocking reuptake; normally dopamine is removed from its site of action after producing its intended effect, but methamphetamine prevents this reuptake, resulting in prolonged action at dopamine receptors and enhanced feelings of motivation, energy, and attention.⁵ Prolonged alterations in neurotransmission often lead to unintended side effects, or effects that the drug has on the body in addition to the intended psychological effects. In order to compensate for the artificial increase in dopamine signaling, the body downregulates endogenous dopamine production when methamphetamine is used repeatedly. This change, combined with the user’s sensitization or tolerance to certain drug effects, often leads a person to use meth in larger doses and more frequently with continuous, repeated use.⁴

Knowledge about specific drug effects and their individual tendencies to develop either tolerance or sensitization can help users to exercise caution and look for signs of drug dependence. For methamphetamine, tolerance occurs to the cardiovascular, appetite-suppressing, and subjective effects, mainly characterized by euphoria. In addition to long-term tolerance in the euphoric drug effect, this drug effect is also subject to “acute tolerance,” which means that users stop perceiving the euphoric state about an hour after administration, despite having a high concentration of the drug in the body for about eleven hours. Acute tolerance occurs within a singular use, and does not require repeated, continuous usage to occur.⁴ Because a user may think that they are no longer under the influence, they may take another dosage or substance to feel the effects again, which can lead to overdose because the drug concentration increases from an already high level. Signs of methamphetamine toxicity include:

• dilated pupils
• bradycardia (slowed heart rate) or tachycardia (quickened heart rate)
• arrhythmia (irregular heart rate)
• chest pains
• shortness of breath
• higher than normal body temperature
• hypertension
• heart attack
• kidney damage
• altered mental status and psychosis
• gastrointestinal distress.

People experiencing methamphetamine toxicity often present with an altered psychological state, which may include delusions, hallucinations, and paranoia. If it is possible that you’re experiencing methamphetamine toxicity, you should seek emergency medical attention immediately, as this state can result in suicidal ideation, seizures, and coma in some cases.¹

The body adjusts to different drug effects uniquely, and in addition to tolerance, the body may sensitize to drug effects, meaning that it experiences the effect in an increased magnitude despite taking the same dosage. For methamphetamine, sensitization occurs with the drug effects of paranoia and psychosis, which may not be experienced with initial uses but potentiate with repeated or continuous drug usage. This means that people who frequently use methamphetamine are at a higher risk of experiencing an episode of drug-induced psychosis with each usage.⁴

While repeated methamphetamine use does not cause vegetative dependence ⁶, it may produce an emotional and psychological addiction in which the user persistently craves the drug and may forgo social, occupational, or recreational activities to spend more time obtaining and ingesting the drug. This behavior, when causing distress to the user’s health and wellness, may be classified as a substance use disorder.⁷ We at SexInfo are not medical professionals, and recommend asking a healthcare or mental health professional for advice on seeking treatment for substance use disorders.

Effects on the Body

In addition to the euphoric psychological effects experienced by users, methamphetamine can have severe drug effects on the physiology of the body and brain. Chronic users may display symptoms such as insomnia, increased movement, appetite suppression, rapid breathing and heartbeat, and high blood pressure.¹ Long-term use may also result in weight loss, dental problems, and sores on the skin caused by scratching. ¹ Users should be mindful of the previously mentioned acute tolerance effect, monitoring for signs and symptoms of methamphetamine toxicity that are listed above.

A growing body of evidence demonstrates that methamphetamine use may worsen the progression of HIV/AIDS in people who are positive. According to a study examining the concentration of metabolites in the brain matter of HIV positive methamphetamine users, the injurious effects of HIV/AIDS and chronic methamphetamine use are consistent with an additive model. This suggests that neural damage is significantly more pronounced when these two factors are combined.⁸ While further research is necessary to outline the specific implications of this damage, some evidence suggests consequential cognitive and motor deficits. Further, those taking antiretroviral medications, commonly prescribed for HIV-positive people, should exercise extreme caution when taking methamphetamine, as the medication may disrupt drug metabolism and result in exaggerated and prolonged drug effects.

Methamphetamine and Sex

More research is needed on the implications of methamphetamine use and sexual function and behavior, as the literature greatly lacks updated findings using representative samples. For example, a majority of the research focuses on the effects of methamphetamine use on people with penises, whereas more research is needed on the sexual and physiological impacts on users with vulvas or uteruses. Strict governmental regulation of the drug presents a significant barrier to conducting research on methamphetamine. In addition, much of the research literature investigating methamphetamine use, and sexual behavior is littered with stigmatized and inaccurate language, contributing negatively to the shame surrounding same-sex sexual behavior and HIV/AIDS. 

Methamphetamine has a significant effect on the chemistry of the brain, and therefore can alter many aspects of one’s behavior and cognition, including judgment, impulsivity, motivation, and perception.^1,2 Due to these changes, users may be less likely to engage in safer sex behaviors, such as remembering to use contraceptive methods and asking their partner about recent screening for sexually transmitted infections.⁹ Users may share needles while injecting drugs, increasing their risk of contracting serologically (body fluids such as blood) transmitted diseases such as HIV (Human Immunodeficiency Virus) or Hepatitis B and C.1 Additionally, users suffering from substance use disorders may engage in dangerous methods of obtaining the substance, such as exchanging unwanted sexual favors for methamphetamine or money.⁹ Crucially, someone under the influence of methamphetamine may not be able to give consent due to the psychologically altering properties of the drug. Thus, one should not engage in sexual behaviors with a partner under the influence of methamphetamine if there is any question of intoxication. Further, effective communication and boundaries should be established in a sober state before engaging in sexual practices while taking a drug. Even with prior establishment of boundaries, it is imperative for partners to remember that consent is revocable at any moment.

Methamphetamine use may also increase one’s sex drive, which, when compounded with altered mental state, may increase one’s likelihood of foregoing safer sex practices in order to more quickly begin sex.¹⁰ Some methamphetamine users report feelings of heightened sexual sensations, perceiving sensations as significantly more intense than sensory experiences without prior drug taking. One study demonstrated that some users of methamphetamine engage in a practice known as a sex “marathon,” which is defined as prolonged engagement in sexual practices over hours or days. During sex marathons on methamphetamine, users may utilize  drug-induced increased sex drive, ability to orgasm multiple times, and delayed ejaculation that often occur as side effects of methamphetamine use.⁹ Increased energy for sexual behavior and sex drive appear to be motivators to continue drug use, as evidenced by a study assessing methamphetamine use and sexual behavior for twenty-five HIV-positive MSM (men who have sex with men). While the majority stated that their motivation to begin methamphetamine use was “to experiment” (40%) and “to party” (35%), participant motivations changed to “to enhance sexual pleasure” (88%) and “to get high” (84%) as they engaged in repeated drug usage.¹¹  Because methamphetamine also alters bodily secretions, it may cause the skin to become dry and more easily lesioned during intercourse. STIs and HIV may be transmitted through skin-to-skin contact and the exchange of bodily fluids (such as semen, vaginal fluid, blood, and breast milk), and even small tears in the delicate tissue of the anal and genital skin create a pathway for bacteria and virus particles to more easily enter the body.⁹ Methamphetamine has also been used to increase the intensity of sexual intercourse. For some users with penises, a prolonged erection is accompanied by delayed ejaculation. This property has made methamphetamine a drug sometimes implicated in sex work.⁹ However, methamphetamine can also cause erectile dysfunction (ED), which may prevent a user with a penis achieving a full erection, a condition known colloquially as “crystal dick.” ⁹ Because methamphetamine use also dries out the skin of the penis, vagina, and anus, further increasing the likelihood  of contamination with virus or bacteria, the use of artificial lubrication is recommended to avoid microtears.⁹  Methamphetamine users adopt a greater chance of contracting HIV due to the unreliability to obtain the pure drug and the use of needles for administration.¹⁰

Methamphetamine and Pregnancy

There is limited research on the impacts of methamphetamine use on pregnancy, as most studies have been conducted on small samples and did not account for co-occurring substance use with other drugs. However, some evidence supports health and developmental risks posed to fetus when exposed to methamphetamine. There is concrete evidence that demonstrates if a pregnant person contracts an STI and does not seek treatment, the infection may be transmitted to the developing fetus.  Infants born to parents on methamphetamine may be more likely to be born preterm, have low birth weight, have heart defects, or be subject to other birth complications, such as cesarean deliveries or even infant mortality.¹² This data cannot be interpreted as causal evidence, however, because the populations in the sample also experience increased rates of other factors correlated with high-risk pregnancies, such as domestic violence, other substance abuse, and poor prenatal care. These experiences may be associated with other health complications that were observed in the infants born to methamphetamine users, such as hypertension, placental abruption, and maternal and neonatal intensive care unit admission.¹² Due to the resultant cardiovascular strain, methamphetamine use is associated with a heightened risk of acute death. Animal studies have shown that methamphetamine can cross the placenta and drug levels are detectable in the fetus’s heart and brain. An increasing body of evidence supports morphological brain impairments with consequential cognitive deficits as a result of prenatal exposure to methamphetamine.¹² A longitudinal study funded by the National Institute on Drug Abuse (NIDA) traced a population of children exposed to methamphetamine during gestation. The results indicated decreased arousal, increased stress, and poor quality of movement in infancy. In the following one to two years, delayed motor development was observed. In the same study, preschool aged children exposed to methamphetamine during fetal development had significant attentional difficulties and cognitive and behavioral issues in school, mostly related to issues of executive function and self-control.³ 

Concluding Remarks

Methamphetamine is an illegal drug with effects of increasing energy, attention, and a temporary euphoric “high” that can be highly addictive.¹ It also has effects on sexual function, such as increased libido, more sensitive sensations, and stimulation of the pleasure centers of the brain due to a large increase in dopamine release.⁹ Methamphetamine’s euphoric effect develops tolerance with repeated use, and its psychotic and paranoia effects develop sensitization.⁵ Methamphetamine users should exercise caution and monitor for the symptoms of methamphetamine toxicity, such as changes in heart rate, chest pain, altered mental status, and gastrointestinal issues. Due to the drug’s resultant impairments in cognitive function, motivation, and attention, users may not be as likely to practice safer sex practices such as using contraception or asking a partner about recent STI screening.⁹ It is possible to develop a substance use disorder involving methamphetamine, which may cause those affected to undergo dangerous methods to obtain the drug.⁷ Additionally, evidence suggests that methamphetamine use may worsen the neurological damage that results from HIV.⁸ Methamphetamine may have negative effects on pregnancy and delivery, such as lower infant weight, preterm birth, and acute death, although more research is needed to substantiate this claim.¹² 

References

1. Yasaei, R., & Saadabadi, A. (2021). Methamphetamine. In StatPearls. StatPearls Publishing.
2. Author Pamela DeCarlo, Robert Guzman. (2006, September). Methamphetamine. Retrieved February 15, 2022, from https://prevention.ucsf.edu/research-project/methamphetamine
3. NIDA. 2019, May 16. Methamphetamine DrugFacts. Retrieved from https://nida.nih.gov/publications/drugfacts/methamphetamine on 2022, February 15.
4. Cruickshank CC, Dyer KR. A review of the clinical pharmacology of methamphetamine. Addiction. 2009 Jul;104(7):1085-99. Epub 2009 Apr 29. PMID: 19426289.
5. Xie, Z., & Miller, G. M. (2009). A receptor mechanism for methamphetamine action in dopamine transporter regulation in brain. The Journal of pharmacology and experimental therapeutics, 330(1), 316–325.
6. Phillips KA, Epstein DH, Preston KL. Psychostimulant addiction treatment. Neuropharmacology. 2014;87:150-160.
7. Stimulant Use Disorder. (2022, January 06). Retrieved February 15, 2022, from https://www.psychdb.com/addictions/stimulants/1-use-disorder
8. Chang L, Ernst T, Speck O, Grob CS. Additive effects of HIV and chronic methamphetamine use on brain metabolite abnormalities. Am J Psychiatry. 2005;162(2):361-369.
9. Semple, Zians, J., Strathdee, S. A., & Patterson, T. L. (2008). Sexual Marathons and Methamphetamine Use among HIV-Positive Men Who Have Sex with Men. Archives of Sexual Behavior, 37(6), 990–990.
10. CW Henderson. (2009). Study findings on HIV/AIDS are outlined in reports from University of California (Sexual Marathons and Methamphetamine Use among HIV-Positive Men Who Have Sex with Men). AIDS Weekly, a11–.
11. Semple, Patterson, T. L., & Grant, I. (2002). Motivations associated with methamphetamine use among HIV men who have sex with men. Journal of Substance Abuse Treatment, 22(3), 149–156.
12. Good, Solt, I., Acuna, J. G., Rotmensch, S., & Kim, M. J. (2010). Methamphetamine Use During Pregnancy: Maternal and Neonatal Implications. Obstetrics and Gynecology (New York. 1953), 116(2, Part 1), 330–334.

Last Updated: March 3, 2022