• P A F Jansen.
• Universitair Medisch Centrum Utrecht, afd. Geriatrie, Postbus 85.500, 3508 GA Utrecht. jansen@azu.nl
• Ned Tijdschr Geneeskd. 2003 Mar 29;147(13):595-9.

AbstractAbout 15% of hospital admissions of elderly patients in the Netherlands are caused by adverse effects of drugs. With polypharmacy there is an increased chance of adverse effects occurring. It is not always possible to reduce polypharmacy in the elderly. Polypharmacy is often associated with drug interactions which result in an increased or decreased effect, or the occurrence of adverse effects. Due to changes in the pharmacokinetic and pharmacodynamic properties of drugs in the elderly, the effect of interactions is more clinically relevant. Pharmacokinetic interactions influence absorption, liver metabolism or excretion by the kidneys. In particular, interactions with drugs that have a narrow pharmacotherapeutic spectrum can result in serious adverse effects: anticonvulsives, anti-Parkinson drugs, antipsychotics, coumarin derivates, digitalis preparations, lithium salts, opiates, sulphonylurea derivates, tricyclic antidepressants and verapamil. The most important pharmacodynamic changes in the elderly concern an increased sensitivity of the target organ. This is particularly the case for substances which have an effect on the central nervous system, such as antidepressants and antipsychotics, but also applies to benzodiazepines, coumarin derivatives and digoxin. When an unexpected adverse effect occurs in a patient or a previously effective therapy suddenly fails, it is wise to consider drug interaction as a possible cause.

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