Amphetamines are a class of central nervous system (CNS) stimulants. These compounds were recognized early for their ability to suppress appetite, leading to their use in weight management. While many early formulations were removed due to safety concerns, certain amphetamine-related compounds remain in use today as restricted, short-term appetite suppressants. They function by altering brain chemistry to reduce hunger and are typically used only when obesity poses significant health risks.
How These Stimulants Affect the Body
Amphetamines and their chemical cousins exert their primary effects by increasing the concentration of specific signaling molecules in the brain. The core mechanism involves the neurotransmitters dopamine and norepinephrine. The medication forces the release of these molecules from storage vesicles within nerve cells and inhibits their reuptake, dramatically increasing their presence in the synaptic cleft.
This surge stimulates the central nervous system, producing a two-pronged effect relevant to weight loss. First, stimulating the hypothalamus, the brain’s appetite control center, suppresses hunger and reduces food cravings (an anorectic effect). Second, the sympathomimetic action—mimicking the sympathetic nervous system—can slightly increase energy expenditure and metabolic rate. The overall weight loss effect is primarily driven by the reduction in caloric intake due to decreased appetite.
Current Therapeutic Use in Weight Management
The current use of these stimulants for obesity is limited to certain chemical analogs of amphetamine. For example, drugs like phentermine, diethylpropion, benzphetamine, and phendimetrazine are specifically approved for weight loss. These compounds are categorized as Schedule III or Schedule IV controlled substances, reflecting a lower potential for abuse compared to classic amphetamine, which is a Schedule II substance.
These medications are reserved for people with a Body Mass Index (BMI) of 30 or greater, or a BMI of 27 or greater combined with weight-related health conditions, such as high blood pressure or diabetes. The treatment duration is strictly short-term, generally limited to a period of 12 weeks or less to mitigate the risk of developing tolerance and dependency.
Acute Physical and Mental Side Effects
Taking amphetamine-like drugs can result in a range of adverse reactions. Due to their stimulant nature, these medications affect the cardiovascular system, often causing an increase in heart rate (tachycardia) and elevated blood pressure. Patients may experience palpitations, which necessitates careful monitoring, especially in those with pre-existing heart conditions.
Common physical discomforts include dry mouth, which can lead to dental problems, and gastrointestinal issues such as nausea, constipation, or abdominal pain. Insomnia and restlessness are also frequent complaints, as the central nervous system stimulation can interfere with normal sleep patterns. Other physical effects may include blurred vision, headaches, and tremors.
The psychological effects can be equally disruptive, impacting mood and cognitive function. Patients may experience nervousness, agitation, and increased anxiety or irritability. In rare cases, particularly with higher doses or misuse, more severe mental health issues can arise, including psychosis, characterized by hallucinations, delusions, and paranoia.
Developing Tolerance and Dependency
A significant long-term concern with these stimulants is the body’s adaptation to the drug, which leads to reduced effectiveness over time. Tolerance is the physiological process where a person requires progressively larger doses of the medication to achieve the original therapeutic effect of appetite suppression. This necessity for dose escalation increases the risk of adverse physical and mental side effects.
Continued use can lead to physical or psychological dependence, meaning the body needs the drug to function normally and cessation results in a withdrawal syndrome. When the medication is abruptly stopped, the acute withdrawal phase can bring on symptoms like fatigue, depression, and an intense craving for the drug. A common physiological rebound effect is a dramatic increase in appetite, which often leads to significant weight regain, negating the drug’s original benefit.