ARX-Nitrofurantoin

What it is

ARX-Nitrofurantoin contains nitrofurantoin macrocrystals in 50 mg and 100 mg capsule strengths. Nitrofurantoin is a synthetic antibacterial nitrofuran derivative. Nitrofurantoin is bacteriostatic at low concentrations and bactericidal in higher concentrations, with its mode of action based upon interference with several bacterial enzyme systems.

Approved indications

— Treatment of urinary tract infections such as cystitis and pyelitis when due to susceptible pathogens.

Dosing overview

Adults receive 50–100 mg four times a day, not to exceed 400 mg daily. Prophylactic therapy is 50 mg or 100 mg at night. Children should receive 5–7 mg/kg body weight per 24 hours in divided doses four times a day. The medicine should be taken with food or milk. Therapy should be continued for at least one week and for at least 3 days after sterility of the urine is obtained.

Key safety warnings

Peripheral neuropathy, including optic neuritis, which may become severe or irreversible, has occurred, with fatalities reported. Conditions such as renal impairment, anaemia, diabetes mellitus, electrolyte imbalance, vitamin B deficiency, and debilitating disease may enhance the occurrence of peripheral neuropathy. If numbness or tingling occurs in any area, administration of the drug should be discontinued. Hepatic reactions, including hepatitis, cholestatic jaundice, chronic active hepatitis and hepatic necrosis occur rarely, with fatalities reported. Patients should be monitored periodically for changes in liver function, and if hepatitis occurs, the drug should be withdrawn immediately. Acute, subacute or chronic pulmonary reactions have been observed and can be life threatening; treatment should be stopped immediately if they occur. Chronic pulmonary reactions can develop insidiously, occur rarely and generally in patients receiving therapy for six months or longer, requiring close monitoring during long-term therapy. Haemolytic anaemia of the primaquine-sensitivity type has been induced by nitrofurantoin, linked to glucose-6-phosphate dehydrogenase deficiency found in 10% of individuals of African descent and in small percentages of ethnic groups of Mediterranean and Near Eastern origin.

Contraindications

ARX-Nitrofurantoin is contraindicated in anuria and oliguria or extensive impairment of renal function (creatinine clearance under 60 mL/min or clinically significant elevated serum creatinine); hypersensitivity to furan derivatives; and should not be administered to pregnant women during labour and delivery, or when the onset of labour is imminent, or to infants under one month of age because of the possibility of producing haemolytic anaemia.

Regulatory history

ARX-Nitrofurantoin 50 mg was first approved on 17 December 2021 (AUST R 373271) and the 100 mg strength on the same date (AUST R 3732710). Both strengths were first listed on the ARTG on 18 January 2022.