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 micrograms/minute (20 subjects), an intermediate rate of 6.66 micrograms/minute (four subjects), and a high rate of 9.99 micrograms/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 micrograms in the low-rate group and 368 micrograms 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 less than .001 between the three groups). After bolus injection, maximum plasma concentrations were significantly different between the three groups (P less than .001) and from their respective baseline values (P less than .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.