From the Guidelines
Yes, macrobid (nitrofurantoin) does get into the blood, but in very low concentrations. Macrobid is primarily used to treat urinary tract infections. It is rapidly absorbed from the gastrointestinal tract and then quickly excreted into the urine, where it reaches high concentrations. Only small amounts enter the bloodstream. The low blood levels of macrobid are actually beneficial, as this reduces systemic side effects while maintaining high levels in the urinary tract where it's needed to fight infection. This is why macrobid is effective for urinary tract infections but not typically used for systemic infections elsewhere in the body. When taking macrobid, it's essential to complete the full prescribed course (usually 5 days) even if symptoms improve, to ensure the infection is fully cleared, as recommended by the American College of Physicians 1. Take it with food to improve absorption and reduce stomach upset. Drink plenty of water while on this medication to help flush the urinary system. Some key points to consider when prescribing macrobid include:
- The choice of antibiotic should be individualized and based on patient allergy and compliance history, local practice patterns, local community resistance prevalence, availability, cost, and patient and provider threshold for failure 1.
- The American College of Physicians recommends short-course antibiotics with either nitrofurantoin for 5 days, trimethoprim–sulfamethoxazole (TMP–SMZ) for 3 days, or fosfomycin as a single dose for women with uncomplicated bacterial cystitis 1.
- The goal of treatment is to minimize morbidity, mortality, and improve quality of life, and the use of macrobid has been shown to be effective in achieving these outcomes in patients with urinary tract infections.
From the Research
Systemic Absorption of Macrobid (Nitrofurantoin)
- The studies provided do not directly address the systemic absorption of Macrobid (Nitrofurantoin) into the bloodstream 2, 3, 4, 5, 6.
- However, the studies discuss the factors that influence drug absorption, including physicochemical properties, physiological factors, and patient-specific variables 2, 4, 5.
- The Biopharmaceutics Classification System is mentioned as a tool for predicting compounds likely to be associated with bioavailability problems 2.
- The extent of absorption can be estimated using various methods, including Fick's principle and a simple pharmacokinetic model 6.
- The studies suggest that drug absorption can be affected by various factors, including gastric emptying rate, intestinal motility, and the presence of other substances such as food or other drugs 4, 5.
- The rate and amount of drug absorbed can vary between patients, even with the same condition, due to individual differences in physiology and disease activity 4.