Macrolide antibiotics (azithromycin and erythromycin)
Two studies investigating macrolide antibiotics have been published.
Prince et al. studied seven patients with morbid obesity receiving a single dose of 250 mg erythromycin within three days before and six weeks after surgery (one gastric bypass, six gastroplasty)49. Mean weight-corrected AUC was reduced with 41% compared to pre-surgery values, with two patients having no detectable serum concentration after surgery. Mean peak concentration decreased from 1.04 to 0.5 ug/ml, and Tmax increased from 3.9 ± 1.5 to 6.7 ± 2.8 hours 49.
Padwall and colleagues studied azithromycin pharmacokinetics in 14 female RYGB surgery patients, and 14 BMI matched controls50. Subjects were administered two 250 mg azithromycin tablets at least three months after surgery. AUC was reduced in the RYGB subjects by 31%, Cmax and Tmax were not significantly altered50.
Since both studies showed a reduction in exposure after surgery, it seems that the use of macrolide antibiotics should be discouraged after bariatric surgery.