Therapeutic drug and biochemical monitoring in a community pharmacy: Part 1

A therapeutic drug and biochemical monitoring service within the primary health care sector could provide positive patient outcomes. We have evaluated the possibility of measurements being made by a community pharmacist. Simultaneous blood samples were taken from a finger prick and vein of 55 patients attending a hospital outpatient clinic. The plasma drug concentrations (digoxin, carbamazepine, phenytoin and theophylline) and biochemical parameters (creatinine, potassium and urea) of these finger prick and venous samples were measured in a community pharmacy using the Ames Seralyzer and Clinimate systems. Similar measurements of the venous samples were made by the biochemistry department of a local hospital. There was no significant difference between the concentrations of the two samples (finger prick and venous) measured in the community pharmacy or between the community pharmacy measurements and those carried out by the hospital biochemistry department. External and internal quality control by the community pharmacist was satisfactory. Interpretation of the measured drug concentrations showed that optimal dosing was achieved in only 58.3, 33.3, 50.0 and 28.3 per cent of patients prescribed carbamazepine, digoxin, phenytoin and theophylline, respectively. Interpretation of biochemical concentrations showed that 38.9 per cent of the patients monitored were either hypo- or hyper-kalaemic; 80 per cent of the monitored patients taking renally excreted drugs required a change in their drug management. Although the patients in this study were attending a hospital outpatient clinic, the results highlight the potential benefit of a therapeutic drug and biochemical monitoring service within the primary health care sector.