A study of the effect of some drugs on the dissolution rate of nitrofurantoin

Determination of the effect of some drugs on the dissolution rate of 70 mg nitrofurantoin was carried out at 37 degrees C in 500 ml dissolution medium. Hexamine, formamol, sodium salicylate, sodium benzoate, nicotinamide, aminophylline, aminophenazone, phenazone and paracetamol were studied. Hexamine was found to increase the dissolution of nitrofurantoin in either water of Sörensen's phosphate buffer (pH = 5). Nicotinamide and sodium salicylate enhanced, as well, the dissolution of the antibacterial agent. However, aminophenazone, formamol, phenazone, paracetamol, sodium benzoate, and aminophylline retarded the dissolution rate of the drug. Spectral studies performed on mixtures of either nitrofurantoin-hexamine or nitrofurantoin-aminophenazone, suggested a possible interaction. Further in-vivo studies are needed to determine the effect of these co-administered drugs on the bioavailability of nitrofurantoin.