BACKGROUND:

Drugs with polimorphism, as rifaximin, may have different pharmacokinetic depending on the polymorph. Rifaximin polymorph-α (alfa) is a non-absorbable antibiotic.

OBJECTIVE:

To investigate if pharmacokinetic of reference rifaximin (α) is different from a generic rifaximin of the Mexican market.

MATERIAL AND METHOD:

A prospective experimental study was done assessing polymorphism with X-ray diffraction, solubility test and pharmacokinetics in Beagle dogs after unique oral dose of 100 mg/kg of each rifaximin.

RESULTS:

Reference rifaximin was a polymorph-α (alfa), while generic rifaximin resulted a polymorph-к (kappa). Solubility profile of both was different, solubility of generic was major than reference rifaximin. Plasma peak concentration (Cmax), area under curve (AUC0-t) and relative bioavailability were 8 to 10 folds higher with generic rifaximin (к) than reference drug (α).

CONCLUSION:

Generic rifaximin has a different pharmacokinetic from the reference rifaximin and the former cannot be considered a non-absorbable antibiotic.

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