General Information About Psychopharmacology in the Medically Ill

There several aspects of psychopharmacology that become especially important when treating a medically ill. In particular, one must be aware of pharmacokinetics especially in light of alterations because of disease states or other medications. absorption can be markedly affected by alterations for gastrointestinal tract's and hepatic disease can affect first pass metabolism. Drug excretion can be influenced by a variety of factors as well, including decreased renal blood flow and hepatic disease. Drug distribution is influenced by a variety of factors including serum pH, protein binding, lipid solubility, and blood flow. Because many drugs our protein bound, hypoalbuminemia can markedly lower the volume of distribution. There are many illnesses that can affect albumin levels, including cirrhosis pneumonia pancreatitis etc. ★ It's a point to remember that acidic drugs (e.g. valproic acid) are largely bound to albumin, whereas more basic drugs (e.g., tricyclic antidepressants, benzodiazepines) tend to bind the globulin.

Because other specialties may not appreciate the extent to which psychiatric medications interact with P450 system, it is important to be aware of significant interactions through major enzyme systems. For this reason, it is generally preferable to choose medications that have minimal impact on the P450 system. conversely, removing a medication under the conditions of polypharmacy can also lead to interactions by the resultant lack of inhibition or induction of an enzyme.

This section is not a substitute for a psychopharmacology course, but will cover aspects that are particularly important in medical psychiatry. An excellent reference book is Clinical Handbook of Psychotropic Drugs .