Drug Interactions between Fosteum and sarecycline

ADJUST DOSING INTERVAL: The bioavailability of oral tetracyclines may be significantly decreased during concurrent administration with zinc-containing products. Therapeutic failure may result. The proposed mechanism is chelation of tetracyclines by the zinc cation, forming an insoluble complex that is poorly absorbed from the gastrointestinal tract. In seven healthy volunteers, simultaneous oral administration of zinc sulfate 200 mg and tetracycline 500 mg resulted in a 30% to 40% reduction in tetracycline serum concentrations compared to administration of tetracycline alone. In the same study, doxycycline absorption was not significantly affected by zinc coadministration. Other studies have reported reductions of greater than 50% in tetracycline absorption in the presence of zinc salts.

MANAGEMENT: Patients receiving an oral tetracycline in combination with zinc-containing products should be advised to separate the times of administration by at least three to four hours. Doxycycline may be an appropriate alternative, since its absorption may not be significantly affected by zinc coadministration.

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Antibiotics may decrease the effects of soy isoflavones such as genistein and daidzein. Soy isoflavones are converted into their active forms in part by intestinal bacteria, thus alteration of the intestinal microflora by antibiotics may decrease availability of activated isoflavones. Data are limited. In a study consisting of 11 children ages 4 to 17 years who were fed a body weight-adjusted dose of soy nuts, the urinary excretion rates for genistein and all native isoflavones combined (i.e., genistein, daidzein, and glycitein) were reduced by 37% and 24%, respectively, during oral antibiotic treatment for infection compared to the healthy state when not on antibiotics. The urinary excretion rate for total isoflavones (i.e., native and activated isoflavones combined) was also reduced by 24% during antibiotic administration. The clinical significance of these changes is unknown. There was some indication that the infectious process itself may have played a role, either by altering the colonic flora or some other mechanism, although the extent is unclear.

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