Bioavailability of ibuprofen from matrix mini-tablets based on a mixture of starch and microcrystalline wax.

The bioavailability of ibuprofen from matrix mini-tablets based on microcrystalline wax and a starch derivative was tested. An oral dose of 300 mg of ibuprofen was administered to healthy volunteers (n=8) in a randomized cross-over study design either as a commercial matrix formulation (Ibu-Slow 600) or as mini-tablets (filled into hard gelatin capsules). The mini-tablets consisted of 60% ibuprofen, 15% Paracera M (wax), 22.5% DDWM (starch) and 2.5% triacetin (lubricant). t50% of the in vitro release was 4.5 and 5 h for the mini-tablet and Ibu-slow formulations, respectively. Both formulations behaved in vivo as sustained-release formulation; their HVDt50%Cmax value was determined at 5.6 and 5.1 h for the mini-tablet and Ibu-slow formulations, respectively. A significantly higher value of Cmax was seen for the mini-tablet formulation, resulting in a relative bioavailability of 116 +/- 22.6% compared to the Ibu-slow matrix. These data demonstrate that the experimental mini-tablets can be used to formulate sustained-release dosage forms.

A prospective study in healthy volunteers of the topical absorption of a 5% rifaximin cream.

Rifaximin, the active ingredient of an antibiotic cream, is a synthetic antibiotic derived from rifamycin and characterized by minimal absorption. In animals, no absorption was detected after topical application on the skin. The question as to whether there is detectable absorption in man by the same administration route is answered by this study in healthy volunteers. One gram of the cream containing 5% rifaximin was massaged on a sizable surface of skin prepared prior to application by mechanical abrasion. Rifaximin concentrations in blood and urine were then determined by means of HPLC-electrochemical-coulometrical detection. Concentrations in all samples being less than 2.5 ng/ml, the method's limit of detection, it is concluded that there is no detectable absorption in man. No adverse reactions were reported during this one day study. The results confirm studies performed in animals which showed that rifaximin is not absorbed and is well tolerated.