Diazepam and lorazepam differ in potency and in the time-course of their action. As a sedative, diazepam 10 mg is equivalent to lorazepam 2-2.5 mg. Diazepam is better absorbed after oral than after i.m. administrations but this does not apply to lorazepam. The clinical effect and amnesia begin more rapidly with diazepam, but last longer following lorazepam. Lorazepam is more effective than diazepam in blocking the emergence sequelae from ketamine. Lorazepam i.v. is followed by a lesser frequency of venous thrombosis.

1 The effect of intravenous cimetidine 200 mg or 400 mg on the absorption of lorazepam 2.5 mg tablet and diazepam 10 mg tablet and capsule was studied. 2 Considerable individual variation in plasma concentrations was found with all preparations. 3 Cimetidine increased the absorption of diazepam and lorazepam. 4 Capsule preparations of diazepam generally produced higher drug plasma concentrations than the tablets.

Cimetidine has been suggested as a new approach to the prevention of the acid pulmonary aspiration syndrome in obstetric anaesthesia. In 20 patients in labour cimetidine 200 mg intravenously did not prolong labour or alter the pattern or strength of uterine contractions. The fetal heart rate did not show any alteration in rate or pattern and it was confirmed that cimetidine crosses the placenta. These findings suggest that further studies of cimetidine in obstetric patients would be safe.

The phenomenon of "acute tolerance" to thiopentone was re-examined in 82 subjects with induction doses of 2-15mg kg-1. There was a strong positive correlation between the venous plasma thiopentone concentrations on recovery from anesthesia and the induction dose, expressed as either mg kg-1 or mg m-2. Recovery time was proportionately shorter with larger doses, being directly related to log10 of the plasma concentration at awakening.

SummaryThe placental transfer of cimetidine 200