Lack of effect of ponsinomycin on the plasma pharmacokinetics of theophylline.

The influence of ponsinomycin on the pharmacokinetics of theophylline has been studied in 12 young healthy volunteers. They received 10 doses of theophylline 200 mg every 8 h p.o., successively in the absence and then in the presence of ponsinomycin. This new macrolide, structurally related to midecamycin, was given in the therapeutic dose of 800 mg b.d. for 5 days, starting 2 days before the second phase of treatment with theophylline. The pharmacokinetic parameters of theophylline, calculated from its plasma concentration at steady-state, were not affected by the co-treatment. In particular, there was no significant difference between the peak and trough plasma levels, apparent clearance or apparent elimination half-life of theophylline in the absence and the presence of ponsinomycin. Only renal clearance was slightly (27%) but significantly increased by the co-treatment. The results suggest that ponsinomycin would be a good choice if a macrolide antibiotic were needed in patients being treated with theophylline.