10. Amphetamines

In the past, amphetamines have been used to treat a number of medical conditions such as epilepsy, obesity, narcolepsy, depression and hyperkinetic children. Since amphetamines were prescribed and promoted quite readily after World War II, people assumed that these drugs were less harmful, if harmful at all. Recent studies, however, have shown amphetamines to be both potentially addictive and quite toxic. Another concern are the recent signs of increased availability and use, and the knowledge that amphetamines can be bought quite cheaply.

The best known members of this group of stimulants in Australia, in decreasing order of potency, are dexamphetamine (eg dexedrine), methamphetamine (eg methedrine) and the amphetamines (eg benzedrine).

Amphetamines are potent sympathomimetic amines of a simple structure with a multiplicity of biological effects that include hyperthermic, anorectic, cardiovascular and central nervous system stimulant actions. The stimulant action of amphetamines is similar to the naturally occurring hormone adrenalin and is thought to work by stimulating and exciting all areas of the nervous system, including the brain.

Since a major action of amphetamines is to inhibit sleep and fatigue, a present concern is the self medication of amphetamines by truck drivers, students and businessmen, who use amphetamines to stave off normal fatigue and enable them to work for days with little sleep or food.

• Young males
• Those who frequent nightclubs – an effect of amphetamine use is that it facilitates energy and activation allowing users to dance all night
  
• Students, particularly at exam time
• Truck drivers – it allows them to drive for long periods without rest and make more trips per week
  
• Those people who are prescribed amphetamines for medical purposes and who develop a dependence for them eg diet pills (Duromine)
• The drug has a reputation of facilitating social and sexual interactions:
  
  • implications for HIV transmission, ie if enhanced sexuality is not accompanied by safer sexual practices
    
  • amphetamines are often used in a casual fashion accompanied by alcohol. The setting is not conducive to the use of clean needles and amphetamine use is an independent risk factor for HIV infection.
• Injecting drug user are increasingly emerging as a polydrug abusing group and as amphetamines are cheaper than heroin on the street more IDUs are including amphetamines in their repertoire of drug use.

• Sensations of euphoria
• Enhanced self awareness and self confidence
  
• Increased visual awareness
• Heightened alertness
  
• Increased capacity for concentration
• Greater energy
  
• Users become hyperactive, talkative, excited, irritable and restless
• Reduction of appetite
  
• Increased breathing and heart rate
• Raised blood pressure
  
• Dilation of the pupils.

• Violent aggressive behaviour
• The use of amphetamines by drivers of heavy road transport vehicles causing serious road vehicle accidents
  
• Spread of HIV and other infections through the use of non-sterile injecting equipment (sharing)
• Belief of users that amphetamines are not harmful and therefore those dependent on amphetamines are unlikely to contact drug services
  
• Amphetamine use by adolescents may affect psychosexual development
• Misdiagnosis of amphetamine psychosis as paranoid schizophrenia
  
• Use can result in criminal activity
• When used to treat hyperkinetic children some children may show an exaggeration of original symptoms as well as experience the side effects associated with amphetamine use.

Tolerance develops to many of the actions of amphetamines. These include euphoria, anorexia, hyperthermia, tachycardia, hypertension and increased excretion of noradrenaline.

Little tolerance seems to develop to the anti-sleep actions of these drugs

Psychostimulant withdrawal is generally described in three phases – crash, withdrawal and extinction. The characteristics of these phases are as follows:

1. Crash – the initial period which classically follows a 'run' of use. The most common effects experienced include fatigue and exhaustion. Effects may last several hours to several days.
2. Withdrawal – this phase may last for a number of weeks or even months and is typically characterised by:
   • lethargy/fatigue
     
   • long but disturbed sleep
     
   • irritability
     
   • strong hunger
     
   • deep depression that may lead to attempted suicide
     
   • fits of violent action
     
   • anxiety attacks
     
   • psychic disruption and loss of self-control which may result in aggression
     
   • headaches
     
   • trouble breathing
     
   • sweating
     
   • muscle cramps
     
   • gastrointestinal cramps
     
   • severe secondary reactions ie influenza, pneumonia.
3. Extinction – normal mood and behaviour is interrupted by episodic craving often in response to conditioned cues. These cravings may last minutes or hours and may continue to occur months or years after cessation of amphetamine use.

   The most florid symptoms usually dissipate within a few days or weeks of cessation of use of amphetamines. Often, a significant improvement in mood, energy, and paranoid thinking occurs within days.

Other symptoms such as normal sleep patterns, memory loss, confusion and paranoid thinking and perceptual abnormalities may persist for perhaps six to twelve months.

After that time, residual symptoms, if present, are generally slight and not disabling, and are noticed primarily by the user.

Abstinence is probably the most important therapeutic device, however, some crises may yield to phenothiazine tranquillisers as first aid despite its risk of lowering seizure threshold. Currently there is a trend for using tricyclic antidepressants as part of the management of psychostimulant dependence.