The effects of methamphetamine are nearly identical to other amphetamines.[30] In low to moderate and therapeutic doses (5-25mg orally)[26], methamphetamine produces typical SNDRA effects and may elevate mood, increase alertness, concentration, and energy, reduce appetite, and promote weight loss. In overdose or during extended binges, it may induce psychosis, breakdown of skeletal muscle, seizures, and bleeding in the brain. Chronic high-dose use can precipitate unpredictable and rapid mood swings, stimulant psychosis (e.g., paranoia, hallucinations, delirium, and delusions), and violent behavior. Recreationally, methamphetamine’s ability to increase energy has been reported to lift mood and increase sexual desire to such an extent that users are able to engage in sexual activity continuously for several days while binging the drug.[31] Methamphetamine is known to possess a high abuse liability (a high likelihood that extratherapeutic use will lead to compulsive drug use) and high psychological dependence liability (a high likelihood that withdrawal symptoms will occur when methamphetamine use ceases). Discontinuing methamphetamine after heavy use may lead to a post-acute-withdrawal syndrome, which can persist for months beyond the typical withdrawal period. At high doses, like other amphetamines, methamphetamine is neurotoxic to human midbrain dopaminergic neurons and, to a lesser extent, serotonergic neurons.[32][33][30] Methamphetamine neurotoxicity causes adverse changes in brain structure and function, such as reductions in grey matter volume in several brain regions, as well as adverse changes in markers of metabolic integrity.[33]
Contraindications
Methamphetamine is contraindicated in individuals with a history of substance use disorder, heart disease, or severe agitation or anxiety, or in individuals currently experiencing arteriosclerosis, glaucoma, hyperthyroidism, or severe hypertension.[26] The FDA states that individuals who have experienced hypersensitivity reactions to other stimulants in the past or are currently taking monoamine oxidase inhibitors should not take methamphetamine.[26] The FDA also advises individuals with bipolar disorder, depression, elevated blood pressure, liver or kidney problems, mania, psychosis, Raynaud’s phenomenon, seizures, thyroid problems, tics, or Tourette syndrome to monitor their symptoms while taking methamphetamine.[26] Owing to the potential for stunted growth, the FDA advises monitoring the height and weight of growing children and adolescents during treatment
Other physical effects
The effects can also include loss of appetite, hyperactivity, dilated pupils, flushed skin, excessive sweating, increased movement, dry mouth and teeth grinding (potentially leading to condition informally known as meth mouth), headache, rapid breathing, high body temperature, diarrhea, constipation, blurred vision, dizziness, twitching, numbness, tremors, dry skin, acne, and pale appearance.[26][45] Long-term meth users may have sores on their skin;[46][47] these may be caused by scratching due to itchiness or the belief that insects are crawling under their skin,[46] and the damage is compounded by poor diet and hygiene.[47] Numerous deaths related to methamphetamine overdoses have been reported.[48][49] Additionally, “[p]ostmortem examinations of human tissues have linked use of the drug to diseases associated with aging, such as coronary atherosclerosis and pulmonary fibrosis”,[50] which may be caused “by a considerable rise in the formation of ceramides, pro-inflammatory molecules that can foster cell aging and death.


