Aminoglycoside usage and monitoring in a Saudi Arabian teaching hospital: a ten-year laboratory audit

BACKGROUND AND OBJECTIVE: In 1989, a therapeutic drug monitoring service was established in Assir Central Hospital, Abha, Saudi Arabia, by the Department of Clinical Pharmacology and Therapeutics of the College of Medicine, King Saud University Abha Branch (now King Khalid University). We report a 10-year follow-up of the results of monitoring the commonly used aminoglycosides (amikacin, gentamycin and tobramycin) obtained from our adult patients on first monitoring. METHOD: Two educational seminars for doctors and nurses were conducted 6 months before the initiation of this study. Drug assay requests were made on specially designed forms. Drug dosages were determined by the attending physicians. Samples for peak and trough drug level determinations were drawn after the fourth dose. The results of first time monitoring were sent to the wards with appropriate comments for dosage modifications where indicated. RESULTS: The results for 2022 patients were analysed. Of these, 929, 899 and 194 were for amikacin, gentamycin and tobramycin, respectively. Therapeutic trough concentrations were 71.2%, 28.3% and 28.3% of patients on amikacin, gentamycin and tobramycin, respectively. A total of 8.8%, 17.6% and 11.9% had trough concentrations considered toxic for amikacin, gentamycin and tobramycin, respectively. Peak therapeutic concentrations were achieved in 31.6%, 42.3% and 39.7% of patients on amikacin, gentamycin and tobramycin. A total of 53.3% of patients on amikacin, 50.3% on gentamycin and 57.2% on tobramycin had peak serum drug concentrations in the subtherapeutic range. Toxic concentrations were noticed mainly in patients aged over 60 years and in the critically ill in the intensive care, coronary care and bums units of the hospital. CONCLUSION: To be cost-effective, intensive therapeutic monitoring of aminoglycosides in adults should continue to be monitored mainly for the old and sick patients in critical care units to optimize patient management.