The safety and cost of famotidine in intensive care patients given the drug by rapid i.v. injection or slow i.v. infusion were studied. All patients admitted to the medical-coronary care and surgical intensive care units (ICUs) at a university teaching hospital over a two-month period who had orders for at least one dose of famotidine injection for any indication were randomly assigned to receive the drug by rapid i.v. injection or slow i.v. infusion via volumetric chamber. Data on patient demographics, drug administration time, adverse effects, cardiovascular variables, and costs (including drug acquisition, supply, and nursing personnel costs) were collected prospectively. Fifty-three patients received famotidine by i.v. injection (a total of 1041 doses) and 52 by i.v. infusion (1006 doses). The mean +/- S.D. duration of famotidine administration was 44 +/- 12 seconds in the i.v.-injection group and 19 +/- 5 minutes in the i.v.-infusion group. Adverse effects possibly related to famotidine occurred in three injection-group patients and two infusion-group patients. No significant difference between the groups in cardiovascular variables (mean arterial pressure, heart rate, and respiratory rate) was noted. Cost savings for the injection group relative to the infusion group totaled $2886 for the two-month study period. Half of the savings came from reduced supply costs and half from reduced personnel costs. The annualized savings to the institution would be about $17,300. Rapid i.v. injection of famotidine appeared to be as safe in ICU patients as giving the drug by slow i.v. infusion and was less costly.