Alkaloids as Drugs of Addiction

Addiction may be defined as a state of intoxication, harmful to the individual and to society, produced by repeated administration of a drug and leading to a compulsion to continue taking it in increasing dosage and to a state of physical or psychic dependence on its effects. Nowadays the term drug dependence is frequently used instead of addiction.  

The causes of addiction are many and complex, but at least two factors must be present—a personality defect in the addict and availability of the drug. In addition to these there is frequently some precipitating factor such as an emotional crisis this is usually something that would be considered trivial by a normal person. 

Addiction to drugs may be associated with any or all of three phenomena (i) tolerance in order to obtain the same effect the dose must be continually increased (ii) physical dependence on the drug, due to the physiological changes which are produced by its continued administration, and which are responsible for the unpleasant withdrawal symptoms when it is withheld (iii) habituation or psychological dependence on the drug, a condition probably arising from the euphoria which it produces (263, 264). 

New drugs are tested for their addictive action by investigation of their ability (i) to cause addiction, (ii) to prevent the onset of withdrawal symptoms in a subject habituated to morphine, and (iii) to give rise to such symptoms when suddenly stopped or challenged by a dose of a narcotic antagonist (265). 

Drugs of addiction may be divided into three classes the narcotic analgesics (e.g., morphine and heroin) the stimulants or psychoenergetics (e.g., cocaine and amphetamine) and the hallucinogens (e.g., mescaline and LSD25). 

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