Psychotropic Drug Interactions

Appendix 1 Some Important Psychotropic Drug Interactions... 

DeVane CL, Nemeroff CB. 2000 Guide to psychotropic drug interactions. Primary Psychiatry 2000 7 40-68. 

Watsky, E. J., and C. Salzman. 1991. Psychotropic drug interactions. Hospital and Community Psychiatry 42 247-56. 

Nayak R, Pandurangi A, Bhogale G, Patil N, Chate S. Asterixis (flapping tremors) as an outcome of complex psychotropic drug interaction. J Neuropsychiatry din Neurosci 2012 24(l) E26-7. 

Sandson NB, Armstrong SC, Cozza KL. An overview of psychotropic drug-drug interactions. Psychosomatics 2005 46 464M94. 

Ensuring that other drugs or treatments are not administered which may interact with the psychotropic drug under investigation (e.g. lithium, electroconvulsive therapy). 

A summary of the main classes of psychotropic drugs metabolized by the P450 enzymes, together with some of the drugs of other classes with which they may interact, is given in Table 3.3. 

Hopefully these few examples will serve to emphasize the importance of a knowledge of the pharmacokinetic features of psychotropic drugs in order to avoid the potentially serious side effects that can result from drug interactions. 

Despite the limited value of measuring plasma psychotropic drug concentrations to assess clinical response, a knowledge of the pharmacokinetics of such a drug can be of value in predicting drug interactions. 

The decision to use a psychotropic drug must take into account the potential risks and benefits. This should be discussed with the patient and/ or carer. Before prescribing, a full evaluation of the symptoms should be made and the diagnosis confirmed. Polypharmacy should be avoided. If a drug combination is necessary, the pharmacod)mamic and pharmacokinetic interactions should be considered. 

Gex-Fabry, M., Balant-Gorgia, A.E., and Balant, L.P. (1997) Therapeutic drug monitoring databases for postmarketing surveillance of drug-drug interactions evaluation of a paired approach for psychotropic medication. Ther Drug Monit 19 1-10. 

Any attempt to memorize hundreds of potential drug interactions to prevent dangerous interactions is unproductive. Rather, a child psychiatrist should have a basic understanding of the types and timing of possible drug interactions and then develop prevention strategies in prescribing psychotropics. These may include... 

For most child psychiatrists, the drug interactions most frequently encountered are interactions with other psychotropics. Fluoxetine inhibits the CYP3A isozymes and thus increase the plasma concentration of the tria-zolobenzodiazepines (alprazolam, midazolam, and triazolam), causing increased psychomotor effects (Shader and Greenblatt, 1995). To avoid unwanted psychomotor effects, the dosage of alprazolam should be decreased when it is coadministered with fluoxetine (Chouinard et ah, 1999). Nefazadone has also been shown to increase the pharmacodynamic effects of triazolam and, to a lesser extent, alprazolam (Chouinard et ah, 1999). 

Drug interactions Proleukin may affect central nervous system function. Therefore interactions could occur following concomitant administration of psychotropic drugs. Concurrent administration of drugs possessing nephrotoxic, myelotoxic, cardiotoxic, or hepatotoxic effects with Proleukin may increase toxicity in these organ systems. Reduced kidney and liver function secondary to Proleukin treatment may delay elimination of concomitant medications and increase the risk of adverse events from those drugs. Beta-blockers and other antihypertensives may potentiate the hypotension seen with Proleukin. 

As with any other medication prescribing there must be awareness of drug interactions, with important ones for methadone relating to antivirals, psychotropics, anticonvulsants and antibiotics. 

Weller R, Preskorn SH. Psychotropic drugs and alcohol pharmacokinetic and pharmacodynamic interactions. Psychosomatics 1984 25 301-309. 

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