[Pharmacologic interactions in chronic treatments: corrective measures for its prevention in a basic area of rural health].

OBJECTIVES

To identify the pharmacological interactions of clinical relevance (PICR) in the medication authorization cards (MAC) of the chronically ill and to establish strategies to minimise their appearance.

DESIGN

Cross-sectional descriptive study.

SETTING

Rural primary care centre.

PATIENTS

Random sample of 626 MAC out of a total of 1306.

MEASUREMENTS AND MAIN RESULTS

In December 1998, the following was gathered for every MAC with more than one drug treatment: age, sex, number of drugs, intrinsic value, drugs prescribed, daily dose and pharmacological interactions (PI), classified (using the scale of Hansten 1996) into light and clinically relevant.

STATISTICAL ANALYSIS

Mantel-Haenszel (alpha = 0.05). Patients' mean age was 69.1 (95% CI, +/- 1.2). Mean number of drugs per MAC was 4 (95% CI, +/- 0.2). 341 PI affecting 197 patients (31.5%, 95% CI, +/- 3.6) were identified. 24.9% (95% CI, +/- 4.5) were PICR, detected in 11.7% (95% CI, +/- 2.5) of the MAC. The existence of PI was related to the number of drugs prescribed to each patient (p < 0.01). There were 26 PI with drugs of low intrinsic value (7.6%; 95% CI, +/- 2.8). 74.1% (95% CI, +/- 9.3) of the total PICR could be avoided by simple recommendations; and the remaining 25.9% (95% CI, +/- 9.3) by monitoring and follow-up of patients.

CONCLUSIONS

It is important to identify the medications most commonly involved in the PICR so as to establish corrective measures to minimise the risks arising from multiple medication. Four educational messages advise on over 60% of the PICR detected.