Drug use and adverse drug reactions in 105 elderly patients admitted to a general medical ward.

OBJECTIVE

To examine the influence of admission to hospital on the number of drugs used by the elderly and to study the occurrence of adverse drug reactions (ADRs), their contribution to the need for hospitalization and the relation to hospital stay.

PATIENTS AND METHODS

Drug use and its sequelae were studied by one observer in 105 patients aged 65 years and older, successively admitted to a general medical ward. Naranjo's algorithm was used to estimate the probability of an ADR. Multiple regression analysis was used to measure interrelationships between variables.

RESULTS

There was a slight but significant increase in drug use per patient (4.9 prescriptions on admission, 5.3 at discharge); 120 ADRs occurred, 57 on admission, 63 during stay. Two ADRs were potentially fatal. Drugs most often involved were diuretics, ADRs occurring mainly on admission. During stay in hospital antimicrobials were mainly responsible. There was a strong correlation of both ADRs on admission and ADRs during stay with duration of hospital stay. ADRs did not correlate with the number of drugs in use on admission or with the number of diagnoses. A direct correlation between the occurrence of ADRs and age could not be confirmed, when corrected for possible confounding factors. Fourteen of 105 admissions were definitely or probably drug-induced; diuretics were incriminated 6 times.

CONCLUSIONS

Drug use per patient corresponded with that in the literature. Thirty-seven per cent of patients experienced a definite or probable ADR. The percentage of drug-induced admissions (14.7%) agrees with the literature, although the drugs involved (mainly diuretics in our study) were markedly different. The occurrence of ADRs, both on admission and during stay is correlated with the duration of hospital stay, but not with drugs in use or with the number of diagnoses.