These have temporary stimulant and euphoriant effects that are followed by depression, anxiety and irritability. Psychological rather than true physical dependence is the rule. In addition to restlessness, over-talkativeness and overactivity, amphetamines can produce a paranoid psychosis indistinguishable from acute paranoid schizophrenia. Ecstasy is another amphetamine derivative (see below).
Cocaine is a eNS stimulant (with similar effects to amphetamines) derived from Erythroxylon coca trees grown in the Andes. In purified form it may be taken by mouth, sniffed or injected. If cocaine hydrochloride is converted to its base (crack) it can be smoked. This is an effective way of obtaining an intense stimulating effect and free-basing has become common. Compulsive use and dependence are thought to occur more frequently amongst users who are free-basing. Dependent users take large doses and alternate between the withdrawal phenomena of depression, tremor and muscle pains, and the hyperarousal produced by increasing doses. Prolonged use of high doses produces irritability, restlessness, paranoid ideation and occasionally convulsions. Persistent sniffing of the drug can cause perforation of the nasal septum.
Hallucinogenic drugs such as lysergic acid diethylamide (LSD), cannabis and mescaline produce distortions and intensifications of sensory perceptions as well as frank hallucinations.
A widely used drug in some subcultures is cannabis, derived from the plant Cannabis sativa. It is not thought to cause physical dependence. The drug, when smoked, seems to exaggerate the pre-existing mood, be it depression, euphoria or anxiety. There is no definite withdrawal syndrome or tolerance. There is disagreement over whether it can produce a psychosis.
‘Ecstasy’ is the street name for 3,4-methylenedioxymethamphetamine (MDMA), a psychoactive phenylisopropylamine, synthesized in Germany early in this century. It is a psychodelic drug which is often used as a ‘dance’ drug. It has a brief duration of action (4-6 hours) and is usually ingested in a dose of 75-150 mg orally. There is anxiety concerning the possibility of MDMA causing permanent brain damage and deaths have been reported from hyperpyrexia, collapse, acute renal and liver failure.
Other drugs of dependence include barbiturates and benzodiazepines. Discontinuing treatment with benzodiazepines may cause withdrawal symptoms such as anxiety, restlessness, tachycardia and sensory disturbances for this reason, withdrawal should be supervised and gradual.
Physical dependence occurs with morphine, heroin and codeine as well as with synthetic and semi-synthetic narcotic analgesics such as methadone and pethidine. These substances display cross-tolerance-the withdrawal effects of one are reduced by administration of one of the others. The psychological effect of such substances is of a calm, slightly euphoric mood associated with freedom from physical discomfort and a flattening of emotional response. This is believed to be due to the attachment of morphine and its analogues to receptor sites in the eNS normally occupied by endorphins. Tolerance to this group of drugs is rapidly developed and marked. Following abstinence it is rapidly lost. The abstinence syndrome consists of a constellation of signs and symptoms that reach peak intensity on the second or third day after the last dose of the opiate. These rapidly subside over the next 7 days. Withdrawal is dangerous in patients with heart disease, tuberculosis or other chronic debilitating conditions.
Narcotic addicts are reported to have a high mortality rate due to acute illness associated with drug abuse. Heart disease (including infective endocarditis), tuberculosis and glomerulonephritis are common causes of death, while tetanus, malaria and acute viral hepatitis B are also causally related to addiction.
The treatment of a narcotic drug overdose requires immediate action. If opioid overdose is suspected, naloxone given intravenously (see p.755) can be lifesaving and diagnostic. There should be an immediate recovery of consciousness or a lightening of the comatose state if the offending agent is an opioid. Care must be taken, however, as opiate antagonists can precipitate violent abstinence symptoms. A constant infusion of naloxone hydrochloride may be required in methadone overdose.
The treatment of chronic dependence is usually directed towards helping the addict to live without drugs. Some who cannot manage such a regimen may be maintained on oral methadone. In the UK, only specially licensed doctors may legally prescribe heroin and cocaine to an addict for maintenance treatment of addiction.
Causes of drug dependence
There is no single cause of drug dependence. Three factors appear important:
1 Availability of drugs
2 A vulnerable personality
3 Social, particularly peer, pressures
Once regular drug taking is established, pharmacological factors are particularly important in determining dependence.