The biliary excretion of aztreonam was studied in 10 post-cholecystectomy patients with T-tube biliary drainage (group A) and four other subjects with obstructive biliary tract disease who had recent placement of external biliary drainage (group B). Maximum biliary levels ranged from 9.7 to 88.2 micrograms/ml (mean, 42.9 +/- 7.9 micrograms/ml) and occurred 2.4 h after injection of a single 1-g dose intravenously. Peak biliary levels observed in group B patients were approximately one-third those in group A. Cumulative 12-h biliary excretion (group B) accounted for 0.18 +/- 0.06% of the total dose. In the same period, urinary excretion accounted for 65 to 72% of the total dose. The lower biliary levels of aztreonam observed in group B patients relative to those in group A suggest that in patients with total biliary tract obstruction the liver may not recover full secretory capacity, at least within 3 to 7 days after biliary decompression.

1 Simultaneous serum and milk samples were collected over a 10-day period from twelve normotensive, lactating subjects who ingested 80 mg nadolol once daily for a period of 5 days. For comparative purposes, serum samples were also collected from seven patients with a history of mild essential hypertension who ingested the same dose of nadolol for a period of 13 days. 2 In lactating subjects, steady-state serum concentrations of nadolol were attained in 3 days. Milk concentrations of nadolol were much higher than serum concentrations starting on Day 3 and throughout the remainder of the study. The mean (+ s.e. mean) steady-state levels of nadolol in milk (356.9 + 40.4 ng/ml) were 4.6 times higher than the mean steady-state levels in serum (77.3 + 6.9 ng/ml). 3 In hypertensive patients, the mean serum concentration of nadolol 24 h after the twelfth dose was 40.3 + 8.2 ng/ml as compared to a mean serum concentration in lactating subjects of 40.7 3.4 ng/ml, 24 h after the fifth dose. Mean serum concentrations in hypertensive patients at 1 and 4 h after the final daily dose were not significantly different from those in lactating subjects. 4 It can be estimated that a 5 kg nursing infant would consume about 2-7% of the daily adult therapeutic dose of nadolol. The data suggest that caution should be exercised in the use of nadolol in lactating patients.

Serum and milk concentrations of aztreonam were studied in 12 lactating, healthy subjects over the 8 h period after the administration of a single intramuscular or intravenous 1 g dose. Milk concentrations of aztreonam were found to be much lower than serum concentrations at all time points after both routes of injection. Peak milk concentrations of aztreonam averaged less than 1% of peak serum concentrations. Times to peak concentrations averaged 6 and 10 times longer in milk than in serum after intramuscular and intravenous injections, respectively. The low milk levels, as well as the previously determined poor oral absorption of aztreonam, suggest a low risk of untoward effects in the nursing infant.

Aztreonam was administered as a single, 3-min, 1-g intravenous infusion to 18 subjects, including 6 with biopsy-proven, primary biliary cirrhosis, 6 with biopsy-proven, stable alcoholic cirrhosis, and 6 age-and sexmatched control subjects with normal hepatic functions. Aztreonam was well tolerated by all subjects. Multiple blood samples and timed, cumulative urine samples were taken for assay of aztreonam content and determination of pharmacokinetic profiles. Protein-free filtrates of serum were also assayed for drug levels. Analyses by microbiological and high-pressure liquid chromatographic procedures gave equivalent results. The kinetic data were described by an open, linear, two-compartment model. There were significant differences in elimination half-life (3.2 verus 1.9 h), serum clearance (0.8 versus 1.1 ml/min per kg), and nonrenal clearance (0.2 versus 0.4 ml/min per kg) between the alcoholic cirrhosis group and the normal control group and in elimination half-life (2.2 versus 1.9 h) between the primary biliary cirrhosis group and the normal control group. There was also a difference in nonrenal clearance between the alcoholic cirrhosis and primary biliary cirrhosis groups (0.2 versus 0.5 ml/min per kg). Although the handling of aztreonam differed in the three groups, the magnitude of the difference would warrant a change in aztreonam dosing only for the alcoholic cirrhosis group. In this group, dose adjustment might be required if long-term therapy with high doses of aztreonam is indicated.