Nitrofurantoin (nitrofurantoin 100 mg) Dailymed

Generic: nitrofurantoin

IMPRINT: 2131 Z 100MG SHAPE: capsule
COLOR: pink

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Description

Nitrofurantoin macrocrystals is a synthetic chemical of controlled crystal size. It is a stable, yellow, crystalline compound. Nitrofurantoin macrocrystals is an antibacterial agent for specific urinary tract infections. It is chemically designated as 1-[[(5-nitro-2-furanyl)methylene]amino]-2,4-imidazolidinedione and has the following structural formula: C8H6N4O5 M.W. 238.16 Each capsule, for oral administration, contains 50 mg or 100 mg of nitrofurantoin macrocrystals. In addition, each capsule contains the following inactive ingredients: corn starch, edible black ink (black iron oxide, D&C Yellow No. 10 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake, FD&C Red No. 40 Aluminum Lake), gelatin, lactose monohydrate, silicon dioxide, sodium lauryl sulfate, talc, titanium dioxide and colorant D&C Red No. 33.

Clinical Pharmacology

Nitrofurantoin macrocrystals is a larger crystal form of nitrofurantoin. The absorption of nitrofurantoin macrocrystals is slower and its excretion somewhat less when compared to nitrofurantoin. Blood concentrations at therapeutic dosage are usually low. It is highly soluble in urine, to which it may impart a brown color. Following a dose regimen of 100 mg q.i.d. for 7 days, average urinary drug recoveries (0 to 24 hours) on day 1 and day 7 were 37.9% and 35%. Unlike many drugs, the presence of food or agents delaying gastric emptying can increase the bioavailability of nitrofurantoin macrocrystals, presumably by allowing better dissolution in gastric juices.

Microbiology

Nitrofurantoin is bactericidal in urine at therapeutic doses. The mechanism of the antimicrobial action of nitrofurantoin is unusual among antibacterials. Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates which inactivate or alter bacterial ribosomal proteins and other macromolecules. As a result of such inactivations, the vital biochemical processes of protein synthesis, aerobic energy metabolism, DNA synthesis, RNA synthesis, and cell wall synthesis are inhibited. The broad-based nature of this mode of action may explain the lack of acquired bacterial resistance to nitrofurantoin, as the necessary multiple and simultaneous mutations of the target macromolecules would likely be lethal to the bacteria. Development of resistance to nitrofurantoin has not been a significant problem since its introduction in 1953. Cross-resistance with antibiotics and sulfonamides has not been observed, and transferable resistance is, at most, a very rare phenomenon. Nitrofurantoin, in the form of nitrofurantoin macrocrystals, has been shown to be active against most strains of the following bacteria both in vitro and in clinical infections (see INDICATIONS AND USAGE):

Gram-Positive Aerobes

Staphylococcus aureus Enterococci (e.g., Enterococcus faecalis)

Gram-Negative Aerobes

Escherichia coli NOTE: Some strains of Enterobacter species and Klebsiella species are resistant to nitrofurantoin. Nitrofurantoin also demonstrates in vitro activity against the following microorganisms, although the clinical significance of these data with respect to treatment with nitrofurantoin macrocrystals is unknown:

Gram-Positive Aerobes

Coagulase-negative staphylococci (including Staphylococcus epidermidis and Staphylococcus saprophyticus) Streptococcus agalactiae Group D streptococci Viridans group streptococci Gram-Negative Aerobes Citrobacter amalonaticus Citrobacter diversus Citrobacter freundii Klebsiella oxytoca Klebsiella ozaenae Nitrofurantoin is not active against most strains of Proteus species or Serratia species. It has no activity against Pseudomonas species. Antagonism has been demonstrated in vitro between nitrofurantoin and quinolone antimicrobial agents. The clinical significance of this finding is unknown.

Susceptibility Tests

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimal inhibitory concentrations (MIC's). These MIC's provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MIC's should be determined using a standardized procedure. Standardized procedures are based on a dilution method1 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of nitrofurantoin powder. The MIC values should be interpreted according to the following criteria: MIC (mcg/mL)Interpretation32Susceptible (S)64Intermediate ( I )128Resistant (R)A report ofSusceptibleindicates that the pathogen is likely to be inhibited if the antimicrobial compound in the urine reaches the concentrations usually achievable. A report ofIntermediateindicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report ofResistant Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard nitrofurantoin powder should provide the following MIC values: MicroorganismMIC (mcg/mL)E. coli ATCC 259224 to 16S. aureus ATCC 292138 to 32E. faecalis ATCC 292124 to 16

Diffusion Techniques

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 300 mcg nitrofurantoin to test the susceptibility of microorganisms to nitrofurantoin. Reports from the laboratory providing results of the standard single-disk susceptibility test with a 300 mcg nitrofurantoin disk should be interpreted according to the following criteria: Zone diameter (mm)Interpretation17Susceptible (S)15 to 16Intermediate (I)14Resistant (R)Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for nitrofurantoin. As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms that are used to control the technical aspects of the laboratory procedures. For the diffusion technique, the 300 mcg nitrofurantoin disk should provide the following zone diameters in these laboratory test quality control strains: MicroorganismZone Diameter (mm)E. coli ATCC 2592220 to 25S. aureus ATCC 2592318 to 22

Indications & Usage

Nitrofurantoin macrocrystals is specifically indicated for the treatment of urinary tract infections when due to susceptible strains of Escherichia coli, enterococci, Staphylococcus aureus, and certain susceptible strains of Klebsiella and Enterobacter species. Nitrofurantoin is not indicated for the treatment of pyelonephritis or perinephric abscesses. To reduce the development of drug-resistant bacteria and maintain the effectiveness of nitrofurantoin macrocrystals and other antibacterial drugs, nitrofurantoin macrocrystals should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Nitrofurantoins lack the broader tissue distribution of other therapeutic agents approved for urinary tract infections. Consequently, many patients who are treated with nitrofurantoin macrocrystals are predisposed to persistence or reappearance of bacteriuria. Urine specimens for culture and susceptibility testing should be obtained before and after completion of therapy. If persistence or reappearance of bacteriuria occurs after treatment with nitrofurantoin macrocrystals, other therapeutic agents with broader tissue distribution should be selected. In considering the use of nitrofurantoin macrocrystals, lower eradication rates should be balanced against the increased potential for systemic toxicity and for the development of antimicrobial resistance when agents with broader tissue distribution are utilized.

Contraindications

Anuria, oliguria, or significant impairment of renal function (creatinine clearance under 60 mL per minute or clinically significant elevated serum creatinine) are contraindications. Treatment of this type of patient carries an increased risk of toxicity because of impaired excretion of the drug. Because of the possibility of hemolytic anemia due to immature erythrocyte enzyme systems (glutathione instability), the drug is contraindicated 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. Nitrofurantoin macrocrystals is contraindicated in patients with a previous history of cholestatic jaundice/hepatic dysfunction associated with nitrofurantoin. Nitrofurantoin macrocrystals is also contraindicated in those patients with known hypersensitivity to nitrofurantoin.

Warnings

Pulmonary Reactions ACUTE, SUBACUTE, OR CHRONIC PULMONARY REACTIONS HAVE BEEN OBSERVED IN PATIENTS TREATED WITH NITROFURANTOIN. IF THESE REACTIONS OCCUR, NITROFURANTOIN MACROCRYSTALS SHOULD BE DISCONTINUED AND APPROPRIATE MEASURES TAKEN. REPORTS HAVE CITED PULMONARY REACTIONS AS A CONTRIBUTING CAUSE OF DEATH. CHRONIC PULMONARY REACTIONS (DIFFUSE INTERSTITIAL PNEUMONITIS OR PULMONARY FIBROSIS, OR BOTH) CAN DEVELOP INSIDIOUSLY. THESE REACTIONS OCCUR RARELY AND GENERALLY IN PATIENTS RECEIVING THERAPY FOR SIX MONTHS OR LONGER. CLOSE MONITORING OF THE PULMONARY CONDITION OF PATIENTS RECEIVING LONG-TERM THERAPY IS WARRANTED AND REQUIRES THAT THE BENEFITS OF THERAPY BE WEIGHED AGAINST POTENTIAL RISKS (SEE RESPIRATORY REACTIONS).

Hepatotoxicity

Hepatic reactions, including hepatitis, cholestatic jaundice, chronic active hepatitis, and hepatic necrosis, occur rarely. Fatalities have been reported. The onset of chronic active hepatitis may be insidious, and patients should be monitored periodically for changes in biochemical tests that would indicate liver injury. If hepatitis occurs, the drug should be withdrawn immediately and appropriate measures should be taken.

Neuropathy

Peripheral neuropathy, which may become severe or irreversible, has occurred. Fatalities have been reported. Conditions such as renal impairment (creatinine clearance under 60 mL per minute or clinically significant elevated serum creatinine), anemia, diabetes mellitus, electrolyte imbalance, vitamin B deficiency, and debilitating disease may enhance the occurrence of peripheral neuropathy. Patients receiving long-term therapy should be monitored periodically for changes in renal function. Optic neuritis has been reported rarely in postmarketing experience with nitrofurantoin formulations.

Hemolytic Anemia

Clostridium difficile-associated diarrhea

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including nitrofurantoin, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile. C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.

Precautions

Information for Patients

Many patients who cannot tolerate microcrystalline nitrofurantoin are able to take nitrofurantoin macrocrystals without nausea. Patients should be advised not to use antacid preparations containing magnesium trisilicate while taking nitrofurantoin macrocrystals. Patients should be counseled that antibacterial drugs including nitrofurantoin macrocrystals should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When nitrofurantoin macrocrystals is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by nitrofurantoin macrocrystals or other antibacterial drugs in the future. Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.

General

Prescribing nitrofurantoin macrocrystals in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

Drug Interactions

Antacids containing magnesium trisilicate, when administered concomitantly with nitrofurantoin, reduce both the rate and extent of absorption. The mechanism for this interaction probably is adsorption of nitrofurantoin onto the surface of magnesium trisilicate. Uricosuric drugs, such as probenecid and sulfinpyrazone, can inhibit renal tubular secretion of nitrofurantoin. The resulting increase in nitrofurantoin serum levels may increase toxicity, and the decreased urinary levels could lessen its efficacy as a urinary tract antibacterial.

Drug & Or Laboratory Test Interactions

As a result of the presence of nitrofurantoin, a false-positive reaction for glucose in the urine may occur. This has been observed with Benedict's and Fehling's solutions but not with the glucose enzymatic test.

Carcinogenesis & Mutagenesis & Impairment Of Fertility

Nitrofurantoin was not carcinogenic when fed to female Holtzman rats for 44.5 weeks or to female Sprague-Dawley rats for 75 weeks. Two chronic rodent bioassays utilizing male and female Sprague-Dawley rats and two chronic bioassays in Swiss mice and in BDF 1 mice revealed no evidence of carcinogenicity. Nitrofurantoin presented evidence of carcinogenic activity in female B6C3F 1 mice as shown by increased incidences of tubular adenomas, benign mixed tumors, and granulosa cell tumors of the ovary. In male F344/N rats, there were increased incidences of uncommon kidney tubular cell neoplasms, osteosarcomas of the bone, and neoplasms of the subcutaneous tissue. In one study involving subcutaneous administration of 75 mg/kg nitrofurantoin to pregnant female mice, lung papillary adenomas of unknown significance were observed in the F1 generation. Nitrofurantoin has been shown to induce point mutations in certain strains of Salmonella typhimurium and forward mutations in L5178Y mouse lymphoma cells. Nitrofurantoin induced increased numbers of sister chromatid exchanges and chromosomal aberrations in Chinese hamster ovary cells but not in human cells in culture. Results of the sex-linked recessive lethal assay in Drosophila were negative after administration of nitrofurantoin by feeding or by injection. Nitrofurantoin did not induce heritable mutation in the rodent models examined. The significance of the carcinogenicity and mutagenicity findings relative to the therapeutic use of nitrofurantoin in humans is unknown. The administration of high doses of nitrofurantoin to rats causes temporary spermatogenic arrest; this is reversible on discontinuing the drug. Doses of 10 mg/kg/day or greater in healthy human males may, in certain unpredictable instances, produce a slight to moderate spermatogenic arrest with a decrease in sperm count.

Pregnancy

Teratogenic Effects

Pregnancy Category B Non-Teratogenic Effects Nitrofurantoin has been shown in one published transplacental carcinogenicity study to induce lung papillary adenomas in the F1 generation mice at doses 19 times the human dose on a mg/kg basis. The relationship of this finding to potential human carcinogenesis is presently unknown. Because of the uncertainty regarding the human implications of these animal data, this drug should be used during pregnancy only if clearly needed.

Labor & Delivery

See CONTRAINDICATIONS.

Nursing Mothers

Nitrofurantoin has been detected in human breast milk in trace amounts. Because of the potential for serious adverse reactions from nitrofurantoin in nursing infants under one month of age, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother (see CONTRAINDICATIONS).

Pediatric Use

Nitrofurantoin macrocrystals is contraindicated in infants below the age of one month (see CONTRAINDICATIONS).

Geriatric Use

In general, the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy should be considered when prescribing nitrofurantoin macrocrystals. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Anuria, oliguria, or significant impairment of renal function (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, care should be taken in dose selection, and it may be useful to monitor renal function.

Adverse Reactions

Respiratory CHRONIC, SUBACUTE, OR ACUTE PULMONARY HYPERSENSITIVITY REACTIONS MAY OCCUR. CHRONIC PULMONARY REACTIONS OCCUR GENERALLY IN PATIENTS WHO HAVE RECEIVED CONTINUOUS TREATMENT FOR SIX MONTHS OR LONGER. MALAISE, DYSPNEA ON EXERTION, COUGH, AND ALTERED PULMONARY FUNCTION ARE COMMON MANIFESTATIONS WHICH CAN OCCUR INSIDIOUSLY. RADIOLOGIC AND HISTOLOGIC FINDINGS OF DIFFUSE INTERSTITIAL PNEUMONITIS OR FIBROSIS, OR BOTH, ARE ALSO COMMON MANIFESTATIONS OF THE CHRONIC PULMONARY REACTION. FEVER IS RARELY PROMINENT. THE SEVERITY OF CHRONIC PULMONARY REACTIONS AND THEIR DEGREE OF RESOLUTION APPEAR TO BE RELATED TO THE DURATION OF THERAPY AFTER THE FIRST CLINICAL SIGNS APPEAR. PULMONARY FUNCTION MAY BE IMPAIRED PERMANENTLY, EVEN AFTER CESSATION OF THERAPY. THE RISK IS GREATER WHEN CHRONIC PULMONARY REACTIONS ARE NOT RECOGNIZED EARLY.

In subacute pulmonary reactions, fever and eosinophilia occur less often than in the acute form. Upon cessation of therapy, recovery may require several months. If the symptoms are not recognized as being drug-related and nitrofurantoin therapy is not stopped, the symptoms may become more severe. Acute pulmonary reactions are commonly manifested by fever, chills, cough, chest pain, dyspnea, pulmonary infiltration with consolidation or pleural effusion on x-ray, and eosinophilia. Acute reactions usually occur within the first week of treatment and are reversible with cessation of therapy. Resolution often is dramatic (see WARNINGS). Changes in EKG (e.g., non-specific ST/T wave changes, bundle branch block) have been reported in association with pulmonary reactions. Cyanosis has been reported rarely.

Hepatic

Hepatic reactions, including hepatitis, cholestatic jaundice, chronic active hepatitis, and hepatic necrosis, occur rarely (see WARNINGS).

Neurologic

Peripheral neuropathy, which may become severe or irreversible, has occurred. Fatalities have been reported. Conditions such as renal impairment (creatinine clearance under 60 mL per minute or clinically significant elevated serum creatinine), anemia, diabetes mellitus, electrolyte imbalance, Vitamin B deficiency, and debilitating diseases may increase the possibility of peripheral neuropathy (see WARNINGS). Asthenia, vertigo, nystagmus, dizziness, headache, and drowsiness also have been reported with the use of nitrofurantoin. Benign intracranial hypertension (pseudotumor cerebri), confusion, depression, optic neuritis, and psychotic reactions have been reported rarely. Bulging fontanels, as a sign of benign intracranial hypertension in infants, have been reported rarely.

Dermatologic

Exfoliative dermatitis and erythema multiforme (including Stevens-Johnson syndrome) have been reported rarely. Transient alopecia also has been reported.

Allergic

Gastrointestinal

Nausea, emesis, and anorexia occur most often. Abdominal pain and diarrhea are less common gastrointestinal reactions. These dose-related reactions can be minimized by reduction of dosage. Sialadenitis and pancreatitis have been reported. There have been sporadic reports of pseudomembranous colitis with the use of nitrofurantoin. The onset of pseudomembranous colitis symptoms may occur during or after antimicrobial treatment (see WARNINGS).

Hematologic

Cyanosis secondary to methemoglobinemia has been reported rarely.

Miscellaneous

As with other antimicrobial agents, superinfections caused by resistant organisms, e.g., Pseudomonas species or Candida species, can occur.

Laboratory Adverse Events

The following laboratory adverse events have been reported with the use of nitrofurantoin: increased AST (SGOT), increased ALT (SGPT), decreased hemoglobin, increased serum phosphorus, eosinophilia, glucose-6-phosphate dehydrogenase deficiency anemia (see WARNINGS), agranulocytosis, leukopenia, granulocytopenia, hemolytic anemia, thrombocytopenia, megaloblastic anemia. In most cases, these hematologic abnormalities resolved following cessation of therapy. Aplastic anemia has been reported rarely.

Overdosage

Occasional incidents of acute overdosage of nitrofurantoin macrocrystals have not resulted in any specific symptoms other than vomiting. Induction of emesis is recommended. There is no specific antidote, but a high fluid intake should be maintained to promote urinary excretion of the drug. It is dialyzable.

Dosage & Administration

Nitrofurantoin macrocrystals should be given with food to improve drug absorption and, in some patients, tolerance.

Adults

50 to 100 mg four times a day - the lower dosage level is recommended for uncomplicated urinary tract infections.

Pediatric Patients

5 to 7 mg/kg of body weight per 24 hours, given in four divided doses (contraindicated under one month of age). Therapy should be continued for one week or for at least 3 days after sterility of the urine is obtained. Continued infection indicates the need for reevaluation. For long-term suppressive therapy in adults, a reduction of dosage to 50 to 100 mg at bedtime may be adequate. For long-term suppressive therapy in pediatric patients, doses as low as 1 mg/kg per 24 hours, given in a single dose or in two divided doses, may be adequate. SEEWARNINGS SECTION REGARDING RISKS ASSOCIATED WITH LONG-TERM THERAPY.

How Supplied

Nitrofurantoin Macrocrystals Capsules USP are available as pink opaque/white opaque capsules, imprinted with Z,50 mgand2130, containing 50 mg nitrofurantoin macrocrystals, packaged in bottles of 100 and 1000 capsules and unit-dose boxes of 100 capsules. Nitrofurantoin Macrocrystals Capsules USP are available as pink opaque capsules, imprinted with Z,100 mgand2131, containing 100 mg nitrofurantoin macrocrystals, packaged in bottles of 100 and 1000 capsules and unit-dose boxes of 100 capsules. Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).

Storage And Handling

Store at 20to 25(68to 77[See USP Controlled Room Temperature].

References

1. National Committee for Clinical Laboratory Standards. Methods For Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically - Third Edition. Approved Standard NCCLS Document M7-A3, Vol. 13, No. 25, NCCLS, Villanova, PA, December 1993. 2. National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Disk Susceptibility Tests - Fifth Edition. Approved Standard NCCLS Document M2-A5, Vol. 13, No. 24, NCCLS, Villanova, PA, December 1993.

Package Label.principal Display Panel Section

DRUG: Nitrofurantoin GENERIC: Nitrofurantoin DOSAGE: CAPSULE ADMINSTRATION: ORAL NDC: 49349-040-04 STRENGTH:100 mg COLOR: pink SHAPE: CAPSULE SCORE: No score SIZE: 16 mm IMPRINT: 14 QTY: 14

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