Is the measurement of blood cimetidine levels useful?

1 Blood cimetidine levels were measured up to 5 h after oral intake of 200 mg cimetidine with breakfast in 13 duodenal, 5 gastric and 15 anastomotic ulcer patients. 2 There were larger inter individual differences in results. The mean peak blood concentrations was 1.14 +/- 0.07 microgram/ml (range 0.54-1.94 microgram/ml), the mean period during which the blood concentration exceeded 0.5 microgram/ml was 141 +/- 11 min (range 23-306 min) and the mean area under the cimetidine blood concentration curve (AUC) was 166 +/- 8 microgram ml-1 min (range 96-280 microgram ml-1 min). Coefficient of variation of these parameters was 33%, 43% and 29% respectively. 3 There were no significant differences in these parameters between non-operated patients and patients with a partial gastrectomy. 4 In 11 patients restudied after 2 to 5 months blood cimetidine levels proved well reproducible; mean coefficient of variation of peak blood levels was 8.5 +/- 2.4%, of time during which blood levels exceeded 0.5 microgram/ml 7.6 +/- 2.5% and of the AUC 5.0 +/- 1.0%. 5 There was no difference in peak blood levels, duration of blood level exceeding 0.5 microgram/ml and blood cimetidine AUC between 24 patients healed after 4 weeks cimetidine therapy and 9 in whom healing took longer. Likewise, there was no evidence of lower blood cimetidine concentrations in 9 patients who relapsed during maintenance cimetidine treatment compared with 24 who did not relapse.