Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Mercury Pharmaceuticals Ltd, Capital House, 85 King William Street, London EC4N 7BL, UK
Pharmacotherapeutic group: Antibacterials for systemic use, nitrofuran derivatives
ATC code: J01XE01
Nitrofurantoin is a broad spectrum antibacterial agent, active against the majority of urinary pathogens. It is bactericidal in renal tissue and throughout the urinary tract. The wide range of organisms sensitive to the bacterial activity include Escherichia coli, Enteroccus faecalis, Klebsiella species, Enterobacter species, Staphylococcus species: (e.g. S. aureus, S. saprophyticus, S. epidermidis).
Clinically, most common urinary pathogens are sensitive to nitrofurantoin. Some strains of Enterobacter and Klebsiella are resistant. Nitrofurantoin is not active against most strains of Proteus species or Serratia species. It has no activity against Pseudomonas species.
Each Macrobid capsule contains two forms of nitrofurantoin. 25% of the dose is macrocrystalline nitrofurantoin which has slower dissolution and absorption than nitrofurantoin microcrystals. The remaining 75% of the dose is microcrystalline nitrofurantoin contained in a powdered blend which on exposure to gastric and intestinal fluids forms a gel matrix resulting in a modified release of active ingredient over time. Combined these systems provide a clinically effective bactericidal urine concentration at therapeutic doses.
Plasma nitrofurantoin concentrations at therapeutic doses of the Macrobid capsule are low, with peak levels usually less than 1 mcg/ml. Nitrofurantoin is highly soluble in urine to which it may impart a brown colour. Unlike many drugs the presence of food or agents delaying gastric emptying increases the bioavailability of the Macrobid capsule.
Approx. 20-25% of the total single dose of nitrofurantoin is recovered from the urine unchanged over 24 hours.
None stated.
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