In vitro release of tetracyclines in presence of H[2] - receptor antagonists

There are a number of drug interactions reported for tetracyclines with many other drugs. In present study in vitro release of five different tetracyclines i.e., tetracycline, demecloctcycline, oxytetracline, methacycline and doxycycline in presence of cimetidine and ranitidine has been studied by USP XX dissolution method. The release of almost all tetracyclines was depressed in presence of cimetidine and ranitidine while in some cases the value were greatly increased due to the formation of charge transfer complexes of the antibiotic with H2-receptor antagonists, which gave absorbance at same wavelengths but with much higher molar absorptivity. An attempt was made to elucidate the mechanism of this effect

Kinetics of copper [II] catalyzedoxidation of iodide by iron [III] orthophenanthroline complex in aqueous solution

Orthophenanthroline [OPT] forms stable complex with Iron[II] at pH 3.5. In presence of Ce[IV] it forms a metal-ligand complex in which Fe is in the form of Fe+++ for short period when mixed in mole ratio of 1:3 [Iron: OPT]. This complex is stable for not more than 30 minutes. At the end, this complex reduces itself back to iron[II]orthophenanthroline [Fe[OPT]3]+2 complex. In present work, this property of iron[III] complex was used to oxidize I-1 to I2. Analysis of [Fe[OPT]3]+2 was carried out at 510 nm to monitor the reduction of [Fe[OPT]3]+3 complex. Copper was used as a catalyst during the described reaction to convert back [Fe[OPT]3]+2. The reaction increased with increase in copper concentration. The conversion of [Fe[OPT]3]+3 to [Fe[OPT]3]+2 followed first order kinetics