Barbiturates Monoamine oxidase inhibitors

Monoamine Oxidase inhibitors (MAOis). Developed in the 1950s, the MAOIs were the first class of antidepressants. Subsequently, in the 1960s, the MAOis were also found to be effective anxiolytics. Unlike benzodiazepines and barbiturates, the MAOis are not addictive however, their onset of action is delayed not by minutes or hours but by 3 weeks or more. 

Drug withdrawal reactions - tricyclic antidepressants, monoamine oxidase inhibitors, benzodiazepines, barbiturates, alcohol, opioids. 

Morphine and other opioids exhibit intense sedative effects and increased respiratory depression when combined with other sedatives, such as alcohol or barbiturates. Increased sedation and toxicity are observed when morphine is administered in combination with the psychotropic drugs, such as chlorpromazine and monoamine oxidase inhibitors, or the anxiolytics, such as diazepam. 

Chlorazepate potentiates the CNS-depressant effects of phenothiazines, narcotics, barbiturates, alcohol, antihistamines, monoamine oxidase inhibitors, general anesthetics, and antidepressants. Concomitant use with cimetidine and possibly disulfiram causes diminished hepatic metabolism of chlorazepate, which increases its plasma concentration. 

Some of the monoamine oxidase inhibitors prolong the hexobarbitone sleeping time in mice, probably because they inhibit barbiturate breakdown by the liver microsomes . An anticonvulsive action has also been reported . The fact that the hydrazine derivatives interact with pyridoxal phosphate and can thus inhibit GABA formation may explain why some of the inhibitors of this type sometimes have a convulsive action also. 

Drug Interactions Barbiturates combine with other CNS depressants to cause severe depression ethanol is the most frequent offender, and interactions with first-generation antihistamines also are common. Isoniazid, methylphenidate, and monoamine oxidase inhibitors also increase the CNS-depressant effects. Other prominent drag interactions occin as a result of the induction of hepatic drug-metabolizing enzymes by barbiturates see above). 

The most frequent side effect for diazepam is somnolence dizziness, ataxia, headache, nervousness, euphoria, and rash occur iess frequently. Excessive use of rectai diazepam may produce rebound seizures (63). Intravenous administration may produce infrequent respiratory depression and hypotension. Other sedative drugs, such as barbiturates, valproate, narcotics, phenothiazines, monoamine oxidase inhibitors, and antidepressants, can potentiate the effects of diazepam. 

Often a single drug will have many metabolites including some which have effects similar to the parent (cyclosporin, chlorpromazine). Microsomal drug metabolism can be stimulated by medications such as the barbiturate phenobarbital or by cigarette smoke. Metabolism may be slowed by medications such as the monoamine oxidase inhibitors which are used in treatment of psychiatric disease. There are genetic and sex-related differences as well as age-related effects which may affect an individual patient s metabolism. 

ASA = aspirin NSAIDs = non-steroidal anti-inflammatory drugs, such as ibuprofen, naproxen, and diclofenac CNS stimulants include drugs such as pseudoephedrine, dextroamphetamine, theophylline, and caffeine MAO = monoamine oxidase CNS depressants include drugs such as benzodiazepines, barbiturates, and ethanol SSRIs = selective serotonin reuptake inhibitors, such as fluoxetine, sertraline, and paroxetine. Antidiabetic agents include drugs such as insulin, glipizide, glyburide, and metformin. 

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