Abstract
We measured famotidine concentrations in plasma and cerebrospinal fluid (CSF) in two hemodialyzed female patients (75 and 67 years) who developed mental confusion after the administration of this H2-receptor antagonist at intravenous (i. v.) doses of 40 and 10mg/day, respectively. All measurements were made during convalescent periods following drainage operation for subdural hematoma. We also measured CSF famotidine concentrations in a male patient (3 years) with normal renal function who was diagnosed as having tuberculous meningitis and given famotidine at an i. v. dose of 40mg/day. The CSF concentrations of famotidine measured in the two mentally confused patients were 160 and 249ng/ml and concomitantly measured plasma famotidine concentrations were 419 and 396ng/ml, respectively. Mental status returned to normal in both cases after cessation of the famotidine therapy. In contrast, the CSF famotidine concentrations of the patient with normal renal function were 10 and 12ng/ml on two separate occasions. These results suggest that famotidine may accumulate in the brain to a level causing mental confusion in patients whose clinical courses are complicated not only by an impaired blood brain barrier but also by severe renal insufficiency. Mental status deterioration may be averted if an appropriate reduction of famotidine dosage is undertaken.
