Psychostimulants: This group includes amphetamine, congeners of amphetamine and cocaine. They have no clinical utility. They are only drugs of abuse.
Psychostimulants cause: (1) elevation of mood (euphoria); (2) a sense of increased self- esteem; (3) physical and mental well-being; (4) decreased appetite, and (5) sleep.
Chronic use of Psychostimulants drugs may lead to reversible psychosis. These drugs also unmask psychotic symptoms in latent schizophrenia. These drugs produce their effects by augmenting central noradrenergic and dopaminergic activity. Amphetamine acts as a dopamine receptor agonist. It also induces neuronal release of dopamine and nor- adrenaline. Cocaine inhibits the neuronal reuptake of dopamine and noradrenaline. So these drugs cause marked increase in the sympathetic activity.
Psychostimulants drugs produce tolerance, and physical dependence. However, abstinence symptoms are not severe.
As Psychostimulants drugs are capable of producing psychosis-like symptoms, they are also called psychotomimetic drugs. They are also known as hallucinogenic agents because of their ability to cause hallucinations. These drugs produce alteration in mood, depersonalization, and a variety of effects on memory and learned behavior.
Following hallucinogenic or Psychostimulants agents are commonly abused:
1. Cannabis sativa (marijuana, hashish, ganja, bhang, charas)
2. Lysergic acid diethylamide (LSD)
5. Psilocybin and psilocin
7. Tryptamine derivatives.
Cannabis is obtained from the hemp plants, cannabis sativa and cannabis indica. The resinous exudate of the tops of the female plant contains the active ingredient, i.e. tetrahydrocannabinol. The resin is known as hashish or charas. Bhang is prepared from the dried leaves and the flowering shoots. Ganja is the resinous mass which is obtained from the small leaves and brackets of inflorescence.
Cannabis induces euphoria, calmness and drowsiness. The individual becomes more sensitive to external stimuli and colour looks more vivid and brighter. The psychostimulants causes depersonalization and difficulty in concentration and thinking. Other acute pharmacological effects are bronchodilatation, tachycardia, hypotension, conjunctival vascular congestion, and decrease in intraocular pressure, antiemetic, analgesic and anticonvulsant effects. Cannabis produces psychological dependence with mild abstinence symptoms (nausea, insomnia, sweating, and tremors).
Potential therapeutic uses of this psychostimulants: Cannabis, tetrahydrocanabinol (THC) or its synthetic derivative, nabilone have potential use in cancer patients on cytotoxic drug therapy due to their antiemetic, analgesic and euphoria actions. Other possible uses are in glaucoma, bronchial asthma and as an anticonvulsant.
Lysergic Acid Diethylamide (LSD) and other Hallucinogens
These Psychostimulants induce a qualitatively similar behavioral profile of actions. They have a disintegrating effect on both inborn and learned behaviour. These drugs cause marked changes in mood with emotional outbursts. Individuals my laugh or cry on slightest provocation. Motivation is impaired. Many subjects experience a fear of disintegration of self. All these drugs may have some sympathomimetic actions such as mydriasis, piloerection, tachycardia, tremor and hyperglycemia.
Phencycidine is related to ketamine. Initially it was introduced to produce dissociative anaesthesia. But now it is a popular drug of abuse because of low cost and easy synthesis.
Tolerance to all hallucinogens occurs quickly. Cross-tolerance is seen between LSD, mescaline and psilocybin but is not present between LSD and phencyclidine. These Psychostimulants produce psychological dependence because the withdrawal symptoms (nausea, diarrhea, sleep disturbances, and tremors) are minor.
They are a new class of psycho therapeutic agents. They facilitate the acquisition of learning and enhance memory retention. Cognition is defined as the process of acquiring, storing artd utilizing intellectual knowledge. These Psychostimulants can overcome or retard cognitive decline which occurs in old age and in some diseased conditions. The disruption of the process of memory consolidation by hypoxia, trauma, seizures, hypoglycaemia and other aversive factors can also be preserved by these drugs. Some neotropic drugs are piracetam, aniracetam, oxiracetam, hydergine, vincamine, meclofenoxate, pentoxiflylline, pyritinol, cyclandate, nicergoline.
Mechanism of Action of Psychostimulants
Pentoxifylline, pyritinol, cyclandate and nicergoline may act as cerebral protectors by improving cerebral circulation and microcirculation. Other drugs may induce neurotransmitter environment conducive to learning, acquisition and memory retention by causing an increase in central cholinergic, noradrenergic and dopaminergic activity with concomitant reduction in serotonin function.
Piracetam is a cydlized derivative of GABA. It was the first nootropic agent to be introduced. It is believed to augment energy utilization and resistance to adverse cellular changes induced by anoxia. It also alters the central neurotransmitter as mentioned above. It is shown to improve mental performance in children and aging individuals with memory deficit. It is devoid of autonomic, motor or behavioral effects.
Dose: 2—3 gm daily in divided doses.
Therapeutic Uses of Psychostimulants
1. Cognitive deficits seen in Alzheimer’s disease and during aging.
2. Learning and attention deficit in children.
3. Coexisting memory deficits in neurological and psychiatric illness.
4. Amnesia following cerebral trauma, drug abuse including alcoholism, seizures, etc.