Amphetamine
Introduction
Amphetamine is a potent central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity. It is also used recreationally and as a performance enhancer. The compound is known for its ability to increase wakefulness and focus, as well as to decrease fatigue and appetite. Chemically, amphetamine is a member of the phenethylamine class and is closely related to methamphetamine, a more potent stimulant.
Chemical Structure and Properties
Amphetamine, chemically known as alpha-methylphenethylamine, has the molecular formula C9H13N. It exists as two enantiomers: levoamphetamine and dextroamphetamine. The latter is the more pharmacologically active form and is often used in medications. The compound is a colorless liquid at room temperature and has a characteristic amine odor. It is soluble in water and organic solvents, making it versatile for various pharmaceutical formulations.
Mechanism of Action
Amphetamine exerts its effects primarily by increasing the concentration of monoamines—dopamine, norepinephrine, and serotonin—in the synaptic cleft. It achieves this through several mechanisms:
1. **Inhibition of Monoamine Transporters:** Amphetamine inhibits the reuptake of dopamine, norepinephrine, and serotonin by binding to their respective transporters. This leads to an increased concentration of these neurotransmitters in the synaptic cleft.
2. **Release of Monoamines:** Amphetamine induces the release of dopamine and norepinephrine from presynaptic neurons by reversing the direction of the transporters.
3. **Inhibition of Monoamine Oxidase (MAO):** At higher concentrations, amphetamine inhibits the activity of MAO, an enzyme responsible for the breakdown of monoamines, thereby prolonging their action.
Pharmacokinetics
Amphetamine is typically administered orally, although it can also be taken via other routes such as intranasal, intravenous, or inhalation. After administration, it is rapidly absorbed from the gastrointestinal tract and distributed throughout the body. The drug has a half-life ranging from 9 to 14 hours, depending on the individual's metabolic rate and urinary pH. Amphetamine is metabolized primarily in the liver by the enzyme CYP2D6, producing several metabolites, including 4-hydroxyamphetamine and norephedrine. These metabolites are excreted in the urine.
Medical Uses
Amphetamine is approved for several medical conditions:
Attention Deficit Hyperactivity Disorder (ADHD)
Amphetamine is one of the most commonly prescribed medications for ADHD. It helps increase attention and decrease impulsiveness and hyperactivity in patients. The drug is available in various formulations, including immediate-release and extended-release tablets and capsules.
Narcolepsy
Amphetamine is used to treat narcolepsy, a condition characterized by excessive daytime sleepiness and sudden sleep attacks. The stimulant properties of amphetamine help to promote wakefulness and reduce the frequency of sleep attacks.
Obesity
Amphetamine has been used as an appetite suppressant in the treatment of obesity. However, due to its potential for abuse and adverse effects, its use for this purpose has declined in favor of other medications.
Recreational Use and Abuse
Amphetamine is also used recreationally for its euphoric and stimulant effects. It is often referred to by street names such as "speed" or "uppers." Recreational use can lead to addiction, characterized by compulsive drug-seeking behavior and use despite harmful consequences. Chronic use can result in severe psychological and physical health issues, including cardiovascular problems, psychosis, and cognitive deficits.
Adverse Effects
The use of amphetamine can lead to a range of adverse effects, which can be categorized into acute and chronic effects:
Acute Effects
- Increased heart rate and blood pressure
- Hyperthermia
- Insomnia
- Anxiety and agitation
- Euphoria
- Decreased appetite
Chronic Effects
- Cardiovascular issues such as hypertension and arrhythmias
- Psychological issues including paranoia, hallucinations, and aggressive behavior
- Cognitive deficits, particularly in memory and executive function
- Weight loss and malnutrition
Legal Status
The legal status of amphetamine varies by country. In the United States, it is classified as a Schedule II controlled substance under the Controlled Substances Act, indicating a high potential for abuse but also recognized medical uses. In other countries, such as the United Kingdom, it is classified as a Class B drug under the Misuse of Drugs Act.
Conclusion
Amphetamine is a powerful CNS stimulant with both therapeutic and recreational uses. While it is effective in treating conditions like ADHD and narcolepsy, its potential for abuse and adverse effects necessitates careful medical supervision. Understanding its pharmacology, therapeutic applications, and risks is crucial for both healthcare providers and patients.