AMPHETAMINES

Classification

amp_structure Amphetamine and methamphetamine are Schedule II drugs included in a group of chemicals called sympathomimetic amines. Amphetamine is widely prescribed for Attention Deficit Hyperactivity Disorder (ADHD). Sympathomimetic amines mimic the effects of endogenous neurotransmitters such as epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine. Also included in this group are various over-the-counter drugs such as phenylpropanolamine, pseudoephedrine, ephedrine as well as the Schedule I drug methylenedioxymethamphetamine (MDMA or Ecstasy). The amphetamines are powerful central nervous system stimulants and can be ingested, injected, snorted, or smoked. Methamphetamine is one of the most commonly abused drugs in the United States. It is readily synthesized, with ephedrine being used as the primary precursor.

Metabolism

Amphetamines are rapidly absorbed from the gastrointestinal tract and are either deactivated by the liver or excreted unchanged in the urine. Methamphetamine is excreted primarily unchanged and a low percentage of the drug is metabolized and excreted as amphetamine. Amphetamine is also excreted largely unchanged. The elimination rate of amphetamines varies with the pH of the urine. At low pH the excretion of unchanged drug increases, while at high pH the excretion of unchanged drug decreases. Amphetamines appear in the urine within a few hours after administration, and can typically be detected for up to 72-96 hours.

Abuse

Amphetamines, particularly methamphetamine, are among the most popular drugs of abuse. Common street names include speed, crank, crystal, meth, and ice. Methamphetamine is frequently smoked in a glass pipe as it is easily volatilized into a gas that is inhaled. Methamphetamine varies in its purity, with highly pure forms gaining notoriety for their rapid, intense, and longer duration effects. The signs and symptoms associated with the abuse of methamphetamine depend upon the amount used and the duration of use. With infrequent or low dose use, a person may experience euphoria, lowered anxiety, talkativeness, decreased appetite, increased sexual arousal, increased alertness, and decreased fatigue. Physiologically there can be increased heart rate and blood pressure. With increased dose or prolonged abuse (either binge or chronic), an individual may experience a set of secondary effects that may include increased anxiety, irritability, aggressiveness, paranoia and hypersexuality. Physiological effects can include dilated pupils, dry mouth, increased body temperature, and tachycardia. In overdose situations, a person may experience hallucinations, coma or death. Crash symptoms typically follow binge abuse of methamphetamine. This phase is marked by extreme fatigue, depression, mental exhaustion and prolonged periods of sleep.

Laboratory drug testing: Methods of Analysis

Immunoassays are common methods for detecting amphetamines in urine. Enzyme immunoassay (EIA) is the most common and detects both methamphetamine and amphetamine to varying degrees of sensitivity and specificity. However, EIA will cross-react with several over-the-counter cold and diet preparations which indicates the importance of confirmatory testing for samples screened presumptively positive by immunoassay tests. Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are reliably sensitive and specific confirmatory methods.

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Drug information data is not definitive and should be used for reference guidelines only.