PHARMACOKINETICS OF SALBUTAMOL IN THE PREGNANT WOMAN AFTER SUBCUTANEOUS ADMINISTRATION WITH A PORTABLE PUMP

Objective: We sought to determine whether subcutaneous administration of salbutamol resulted in plasma levels comparable to those achieved after intravenous or oral administration. Methods: Twenty-nine women with preterm labor received subcutaneous infusion of salbutamol through a portable pump. We used three different rates of continuous infusion: a low rate of 3.33-mu-g/minute (20 subjects), an intermediate rate of 6.66-mu-g/minute (four subjects), and a high rate of 9.99-mu-g/minute (five subjects). Plasma salbutamol concentrations were assayed by high-performance liquid chromatography after 48 hours of continuous infusion in the subcutaneous tissue and after bolus injections (184-mu-g in the low-rate group and 368-mu-g in the intermediate- and high-rate groups). Results: Plasma salbutamol concentrations after 48 hours of subcutaneous infusion increased almost linearly with the rate of infusion: 6.29 +/- 1.58, 15.5 +/- 1.0, and 21.7 +/- 4.26 ng/mL in the low-, intermediate-, and high-rate groups, respectively (P < .001 between the three groups). After bolus injection, maximum plasma concentrations were significantly different between the three groups (P < .001) and from their respective baseline values (P < .001): 8.33 +/- 1.9, 18.85 +/- 2.0, and 25.86 +/- 4.8 ng/mL in the low-, intermediate-, and high-rate groups, respectively. Conclusion: Subcutaneous tocolysis can provide plasma salbutamol levels similar to the levels obtained orally or intravenously.