Nitrofurantoin microcrystalline

Fig. 4 Mean cumulative urinary excretion of nitrofurantoin after oral administration of a 100-mg macrocrystalline capsule of fasting (O) and nonfasting ( ) subjects and a 100-mg microcrystalline tablet to fasting ( ) and nonfasting ( ) subjects. Vertical bars represent standard errors of the mean. (From Ref. 7.).

The effect of particle size reduction on the bioavailability of nitrofurantoin was shown in Fig. 4. The microcrystalline form (< 10 pm) is more rapidly and completely absorbed from the tablet dosage form than is the macrocrystalline form (74-177 pm) from the capsule dosage form. This is not a completely satisfactory illustration of the effect of particle size on the rate and extent of availability, since other manufacturing variables have not been held constant. Nevertheless, it does suggest some correlation between particle size, dissolution rate, and rate of availability. 

The incidence of gastrointestinal side-effects including nausea, vomiting and diarrhoea with nitrofurantoin is as high as 30% with standard microcrystalline formulations and patients should be advised to take the doses with food. Other important but less common adverse reactions include pulmonary fibrosis, peripheral neuropathy and hypersensitivity. Patients should also be warned that nitrofurantoin can colour the urine yellow or brown. 

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