Reduced bioavailability of oral amoxicillin tablets compared to suspensions in RYGB bariatric subjects.

BACKGROUND/OBJECTIVES: To evaluate the relative bioavailability of oral amoxicillin (AMX) tablets in comparison to AMX suspension in Roux-en-Y gastric bypass (RYGB) bariatric subjects.

SUBJECTS/METHODS: A randomized, double-blind, cross-over study on the bioavailability of oral AMX tablets and suspension in RYGB subjects at least 3 months previously operated was performed. Doses of 875 mg of the AMX tablet or 800 mg of the AMX suspension were given to all the subjects, allowing a washout of 7 days between the periods. Blood samples were collected at 0, 0.25, 0.5, 1, 1.5, 2, 4, 6 and 8 hours after drug administration and the AMX levels were quantified by LC-MS/MS. The pharmacokinetic parameters were calculated by non-compartmental analysis, normalized to an 875 mg dose and the bioavailability of the AMX from the tablets was compared to that from the suspension formulation.

RESULTS: Twenty subjects aged 42.65 ± 7.21 years old and with a body mass index (BMI) of 29.88 ± 4.36 kg/m2 were enrolled in the study. The AMX Cmax of the tablets and the suspension (normalized to 875 mg) were 7.42 ± 2.99 mg/L and 8.73 ± 3.26 mg/L (CI 90% of 70.71-99.11), and the AUC0-inf were 23.10 ± 7.41 mg.h/L and 27.59 ± 8.32 mg.h/L (CI 90% of 71.25 - 97.32), respectively.

CONCLUSIONS: The tablets presented a lower bioavailability than the suspension formulation and the total absorbed amount of AMX in these subjects was lower in comparison to the standard AMX absorption rates in non-bariatric subjects, regardless of the formulation.