Foetal safety of nitrofurantoin macrocrystals therapy during pregnancy: a retrospective analysis

Findings from the National Birth Defects Prevention Study: Interpretation and translation for the clinician

BACKGROUND

The National Birth Defects Prevention Study (NBDPS) is a large U.S. multi-site case-control study first established in 1996 to identify potentially preventable environmental causes and genetic risk factors for more than 30 selected categories of major birth defects.

METHODS

Numerous reports with both positive and negative findings have been produced by the NBDPS, and many have influenced clinical practice. Many NBDPS reports have included novel findings, and in some cases these findings could only be considered hypothesis-generating. Other reports have met criteria for causality such as replication of findings in other studies, biological plausibility, and coherence.

RESULTS

However, translation of even strongly supported associations, in some cases, has required clinicians to learn to communicate information to patients about small and uncertain absolute risks in the context of the potential effects of under- or poorly treated maternal conditions.

CONCLUSION

The NBDPS has continued to play an important role as a rich U.S. data source that can advance the understanding of maternal conditions and their treatments in relation to birth defects.

Role of Old Antibiotics in the Era of Antibiotic Resistance. Highlighted Nitrofurantoin for the Treatment of Lower Urinary Tract Infections

Bacterial infections caused by antibiotic-resistant isolates have become a major health problem in recent years, since they are very difficult to treat, leading to an increase in morbidity and mortality. Nitrofurantoin is a broad-spectrum bactericidal antibiotic that, through a complex mode of action which is not completely understood, affects both Gram-negative and Gram-positive bacteria. Nitrofurantoin has been used successfully for a long time for the prophylaxis and treatment of acute lower urinary tract infections in adults, children and pregnant women, but the increased emergence of antibiotic resistance has made nitrofurantoin a suitable candidate for the treatment of infections caused by multidrug-resistant pathogens. Here, we review the mechanism of action, antimicrobial spectrum, pharmacology and safety profile of nitrofurantoin. We also investigate the therapeutic use of nitrofurantoin, including recent data which highlight its role in the management of community urinary tract infection, especially in cases of multidrug-resistant isolates, in which oral active antimicrobials are limited resources nowadays.

Pharmaceutical Agents and Pregnancy in Urology Practice

Urologic medical conditions are not frequently encountered during pregnancy. Still, urologists often are asked to treat pregnant patients for conditions that require prescriptions. In the generally healthy population of pregnant women, the use of pharmaceutical agents is usually reserved for women who have either infections or necessary surgical procedures. This article addresses the implications for pregnancy of common urologic conditions in generally healthy pregnant women, namely simple urinary tract infections that demand nitrofurantoin and complex urinary tract infections that necessitate fluoroquinolones treatment. It also examines the implications of nonobstetric surgical intervention.

Effects of antibacterials on the unborn child: what is known and how should this influence prescribing

Antibacterials are among the most commonly prescribed drugs worldwide. In general, infections occur in pregnant women at much the same rate as in the general population. However, as a result of physiological changes brought about by pregnancy, some infections, such as those of the urinary tract, may have an increased incidence. It is important to remember that almost every drug crosses the placenta, ensuring that the unborn fetus is also exposed. When prescribing an antibacterial agent to a pregnant woman, it is important that the mother is treated appropriately while at the same time protecting the unborn child. Certain factors need to be addressed, such as the possible teratogenic risk, changes in pharmacokinetics and the potential toxicity of the drug. In this paper we have reviewed various classes of antibacterials which are commonly used during pregnancy, including penicillins, beta-lactam inhibitors, cephalosporins, macrolides, aminoglycosides, tetracyclines, lincosamides, fluoroquinolones, sulfonamides, nitrofurans, and anti-tubercular agents. Some of these drugs have been on the market for many years, whereas others are relatively new and increasingly popular, despite the fact that the older drugs remain very effective. After reviewing the evidence-based information from epidemiological studies, it appears that most antibacterial agents can be used relatively safely during pregnancy. Women who are pregnant should not be denied appropriate antibacterial therapy because of a lack of information. It is possible to treat the mother, while protecting the unborn child, by prescribing an agent that the causative bacteria is sensitive to, rather than a perceived 'safer' option that may not effectively treat the infection and which may also add to the growing problem of bacterial resistance.

Nitrofurantoin and congenital abnormalities

OBJECTIVE

To study human teratogenic potential of oral nitrofurantoin treatment during pregnancy.

MATERIALS AND METHODS

Pair analysis of cases with congenital abnormalities and matched population controls in the population-based dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-1996.

RESULTS

Of 38,151 pregnant women who had newborn infants without any congenital abnormalities (population control group), 774 (3.4%); of 22,865 case pregnant women who had newborns or fetuses with congenital abnormalities, 1079 (2.8%) and of 812 pregnant women who had newborns or fetuses with Down's syndrome (patient controls), 23 (2.8%) pregnant women were treated with nitrofurantoin. The above differences between population controls and cases may be connected with recall bias, because the case-control pair analysis did not indicate a teratogenic potential of nitrofurantoin use during the second and the third months of gestation, i.e. in the critical period for major congenital abnormalities.

CONCLUSION

Treatment with nitrofurantoin during pregnancy does not present detectable teratogenic risk to the fetus.

The safety of nitrofurantoin during the first trimester of pregnancy: meta-analysis

Asymptomatic bacteriuria is common during pregnancy and may adversely affect both the mother and her fetus. Nitrofurantoin (NF) has been long recognized as an effective agent in both nonpregnant and pregnant women suffering from urinary tract infections. This meta-analysis was conducted in order to evaluate the safety of NF ingested during early pregnancy. Of twenty-two studies, only four met the inclusion criteria and their analysis could not demonstrate any significant correlation between NF ingestion and fetal malformation. The pooled odds ratio was 1.29 with 95% confidence interval 0.25-6.57. Although the number and quality of the studies included are limited, we thought it important to present the existing data. More extensive controlled studies are urgently needed in order to increase the significance of our study.

Nitrofurantoin

For more than 30 years nitrofurantoin has been a widely prescribed and effective agent in the treatment of urinary tract infections. During this time, it has withstood the rigors of constant clinical evaluation and has competed successfully with more recent antibacterial agents. As with many widely used drugs, some serious and potentially hazardous reactions to therapy have been documented. This article reviews and analyzes major reported reactions and interactions from both published and unpublished sources. Incidence rates have been calculated for pulmonary, hepatic, neurological, and hematological responses. Calculated rates of occurrence were very low, and ranged from 0.001 percent of courses of therapy (all types of pulmonary reactions combined) to 0.0007 percent (neurological reactions). Reports on interactions of nitrofurantoin with alcohol, antacids, and oral contraceptives are unfounded and anecdotal. Interactions with nalidixic and oxolinic acids are not clinically significant, and only one case of interaction has been reported with phenytoin. Bioavailability is enhanced by food or propantheline. False positives occur with Benedict's test for urine glucose estimations.

General reproduction, perinatal-postnatal, and teratology studies of nitrofurantoin macrocrystals in rats and rabbits

Urinary tract infections in pregnant women are common and require prompt, effective treatment. Currently, no antibacterial agents have received regulatory approbation for use without restriction during pregnancy. The choice of a drug for use in pregnant women requires careful examination of its possible maternal and fetal toxicity as well as its teratogenic potential. We conducted studies to determine the effects of nitrofurantoin macrocrystals (Macrodantin, Norwich Eaton Pharmaceuticals, Inc.), a synthetic antibacterial, on reproductive capability, fetal development, and neonatal survival in the rat and the rabbit. Doses of 10.0, 20.0, and 30.0 mg/kg.d, approximately 2, 4, and 6 times the daily human therapeutic dose, were administered orally in a methylcellulose suspension to rats and rabbits in general reproduction, perinatal-postnatal, and teratology studies. Safety was assessed by evaluating reproductive capability, fertility, gestation period, fetal and neonatal death, litter size and viability, birth weight and postnatal growth, and malformations. Under the conditions of these studies, treatment with nitrofurantoin macrocrystals in rats and rabbits before or during pregnancy or during lactation caused no adverse effects in the mother, fetus, or neonate. These findings support the premise that nitrofurantoin macrocrystals constitute a safe treatment for urinary tract infection during pregnancy.