Drug Classification: Drug dependence

Methadone

UNDER REVIEW (September 2016)

Mechanism of Action:

Methadone is a synthetic opioid analgesic with similar mechanism of action to that of morphine (mu opioid receptor agonist). Because of its slow metabolism and very high lipid solubility, methadone is longer lasting than morphine-based drugs. Methadone has a typical half life of 24 hours or more, permitting administration only once a day in heroin detoxification and maintenance programs. Methadone is almost as effective when administered orally as by injection. Tolerance and dependence may develop, and withdrawal symptoms, though they develop more slowly and are less acutely severe than those of morphine and heroin, are more prolonged.

 

Nicotine

UNDER REVIEW (September 2016)

Mechanism of Action:

Nicotine mimics the affects of acetylcholine at nicotinic AChRs in the autonomic nervous system, and within the CNS. Nicotine can cause heart palpitations, lowered blood pressure, nausea, and dizziness. A person who smokes inhales approximately 3 mg from one cigarette. This amount increases the heart rate, constricts the blood vessels, and acts on the central nervous system, imparting a feeling of alertness and well-being. Although not considered carcinogenic, nicotine probably contributes to the increased incidence of heart disease seen in smokers and may enhance the growth of tumors caused by carcinogens. People who use tobacco products develop a physiological addiction to nicotine. Research has shown that nicotine increases the flow of the neurotransmitter dopamine in the brain, creating pleasurable feelings and a craving to keep in the bloodstream levels of nicotine that will maintain these feelings. Lack of nicotine causes withdrawal symptoms (heart rate and blood pressure changes, sleeping problems, brain wave disturbances, and anxiety) in smokers. Nicotine replacement therapy is used to reduce these withdrawal symptoms

Lecture and CAL materials:

Disulfiram

UNDER REVIEW (September 2016)

Mechanism of Action:

Disulfiram blocks the enzyme acetaldehyde dehydrogenase which is involved in the metabolism of alcohol. Under normal metabolism, alcohol is broken down in the liver by the enzyme alcohol dehydrogenase to acetaldehyde, which is then converted by the enzyme acetaldehyde dehydrogenase to the harmless acetic acid. Disulfiram blocks this reaction at the intermediate stage leading to the build up of acetaldehyde.

Lecture and CAL materials: