Use in Pregnancy: The safety of Furoxone (furazolidone) during the childbearing age has not been established; as with any potent antibacterial, Furoxone (furazolidone) must be administered with caution during the childbearing age. However, animal breeding studies have revealed no evidence of teratogenicity following the administration of Furoxone (furazolidone) for long periods of time and at doses far in excess of those recommended for the human. There have been no clinical reports regarding this possible adverse effect on the fetus or the newborn infant.
Monoamine Oxidase Inhibition
Effective inhibition of monoamine oxidase by furazolidone has been demonstrated experimentally in man by the enhancement of tyramine and amphetamine sensitivity and by the directly measured monoamine oxidase inhibition.
A period of five days of furazolidone administration in the recommended doses in these patients was required to give an enhancement of the tyramine and amphetamine sensitivities by two to threefold. Administration of furazolidone in the recommended dose of 400 mg/day for a period of five days should not subject the adult patient to an undue hazard of hypertensive crisis due to monoamine oxidase inhibition. Hypertensive crises have never been reported even after the peroral administration of larger doses and/or for longer periods of time. Controlled studies reveal no signs or symptoms of hypertensive crisis even after the peroral administration of Furoxone (furazolidone) in doses of 400 mg/day in excess of 48 consecutive months.
If administered in doses larger than recommended or in excess of five days, the indications must be weighed against the possible hazards of hypertensive crisis related to the accumulation of monoamine oxidase inhibition. If indications are sufficient, the patients should be informed of drugs and foods which predispose to hypertensive crises:
(A) Other known M.O. drugs; however, when indicated they should be prescribed with caution and at a reduced dosage.
(B) Tyramine-containing foods such as broad beans, yeast extracts, strong unpasteurized cheeses, beer, wine, pickled herring, chicken livers, and fermented products are contraindicated.
(C) Indirectly-acting sympathomimetic amines such as those found in nasal decongestants (phenylephrine, ephedrine) and anorectics (amphetamines) are contraindicated.
(D) Likewise, sedatives, antihistamines, tranquilizers, and narcotics should be used in reduced dosages and with caution.
Orthostatic hypotension and hypoglycemia may occur.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Furazolidone has shown evidence of tumorigenic activity in several studies involving chronic, high- dose oral administration to rodents. Promotion of the development of mammary neoplasia has been demonstrated in rats of two strains. Prominent among the findings in mice was that furazolidone caused significant increases in malignant lung tumors. The relevance of these animal findings, particularly in relationship to short-term therapy in humans, is not established.