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Author: Admin | 2025-04-28
Therapy in elderlypatients should be considered when prescribing Macrobid. This drug is known to be substantially excreted by the kidney, and the risk oftoxic reactions to this drug may be greater in patients with impaired renal function. Anuria, oliguria, or significant impairment of renalfunction (creatinine clearance under 60 mL per minute or clinically significant elevated serum creatinine) are contraindications (see CONTRAINDICATIONS). Because elderly patients are more likely to have decreased renal function, it may be useful to monitor renalfunction. Overdose Information for MacrobidOccasional incidents of acute overdosage of nitrofurantoin have not resulted in any specific symptoms other than vomiting. Induction ofemesis is recommended. There is no specific antidote, but a high fluid intake should be maintained to promote urinary excretion of the drug.Nitrofurantoin is dialyzable.Contraindications for MacrobidAnuria, oliguria, or significant impairment of renal function (creatinine clearance under 60 mL per minute or clinically significant elevatedserum creatinine) are contraindications. Treatment of this type of patient carries an increased risk of toxicity because of impaired excretionof the drug.Because of the possibility of hemolytic anemia due to immature erythrocyte enzyme systems (glutathione instability), the drug iscontraindicated in pregnant patients at term (38 to 42 weeks gestation), during labor and delivery, or when the onset of labor is imminent.For the same reason, the drug is contraindicated in neonates under one month of age.Macrobid is contraindicated in patients with a previous history of cholestatic jaundice/hepatic dysfunction associated with nitrofurantoin.Macrobid is also contraindicated in those patients with known hypersensitivity to nitrofurantoin. Clinical Pharmacology for MacrobidEach Macrobid capsule contains two forms of nitrofurantoin. Twenty-five percent is macrocrystalline nitrofurantoin, which has slowerdissolution and absorption than nitrofurantoin monohydrate. The remaining 75% is nitrofurantoin monohydrate contained in a powder blendwhich, upon exposure to gastric and intestinal fluids, forms a gel matrix that releases nitrofurantoin over time. Based on urinarypharmacokinetic data, the extent and rate of urinary excretion of nitrofurantoin from the 100 mg Macrobid capsule are similar to those of50 mg or 100 mg Macrodantin® (nitrofurantoin macrocrystals) capsule. Approximately 20% to 25% of a single dose of nitrofurantoin isrecovered from the urine unchanged over 24 hours.Plasma nitrofurantoin concentrations after a single oral dose of the 100 mg Macrobid capsule are low, with peak levels usually less than 1mcg/mL. Nitrofurantoin is highly soluble in urine, to which it may impart a brown color. When Macrobid is administered with food, thebioavailability of nitrofurantoin is increased by approximately 40%.MicrobiologyNitrofurantoin is a nitrofuran antimicrobial agent with activity against certain Gram-positive and Gram-negative bacteria.Mechanism Of ActionThe mechanism of the antimicrobial action of nitrofurantoin is unusual among antibacterials. Nitrofurantoin is reduced by bacterialflavoproteins to reactive intermediates which inactivate or alter bacterial ribosomal proteins and other macromolecules. As a result of suchinactivations, the vital biochemical processes of
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