Algorithms for determining drug-drug interactions are described. They handle all the generic drugs in the British National Formulary (BNF) (Number 5, British Medical Association and Pharmaceutical Society of Great Britain, 1984) and allow these drugs to be identified by generic or trade name. They also accept and identify interactions for compound drugs prescribed by a single trade name. The algorithms can be implemented on any microcomputer and in a number of languages. The choice of algorithm and number of drugs handled depend on size and disk storage of the microcomputer. It was tested in collaboration with the Department of Geriatric Medicine, Liverpool University, and is used in a prescribing monitoring system operational in some wards of the Royal Liverpool Hospital. The drug data are stored in the form given in the BNF and can be easily updated from this publication. The algorithms can also handle drug allergies and cross-sensitivities. Q 1987 Academic press, Inc.
A drug interaction occurs when a patient takes two or more drugs at the same time, and one drug modifies the action of other. The result of the interaction may be to increase the effect of one of the drugs, potentiation, or to decrease the effect of one of the drugs, antagonism. Occasionally some entirely new effect may be produced. A few interactions are potentially lethal, some are dangerous, and many may lead to suboptimal treatment.
The possibility of drug interactions occurring obviously increases with the number of drugs a patient takes simultaneously.
Drug interactions are more frequent in elderly patients who are more likely to be receiving treatment simultaneously for two or more conditions than the general population and consequently more likely to be taking two or more drugs at the same time. They