Cancer after exposure to metronidazole

Giardia duodenalis: Biology and Pathogenesis

Giardia duodenalis captured the attention of Leeuwenhoek in 1681 while he was examining his own diarrheal stool, but, ironically, it did not really gain attention as a human pathogen until the 1960s, when outbreaks were reported. Key technological advances, including in vitro cultivation, genomic and proteomic databases, and advances in microscopic and molecular approaches, have led to an understanding that this is a eukaryotic organism with a reduced genome rather than a truly premitochondriate eukaryote. This has included the discovery of mitosomes (vestiges of mitochondria), a transport system with many of the features of the Golgi apparatus, and even evidence for a sexual or parasexual cycle. Cell biology approaches have led to a better understanding of how Giardia survives with two nuclei and how it goes through its life cycle as a noninvasive organism in the hostile environment of the lumen of the host intestine. Studies of its immunology and pathogenesis have moved past the general understanding of the importance of the antibody response in controlling infection to determining the key role of the Th17 response. This work has led to understanding of the requirement for a balanced host immune response that avoids the extremes of an excessive response with collateral damage or one that is unable to clear the organism. This understanding is especially important in view of the remarkable ranges of early manifestations, which range from asymptomatic to persistent diarrhea and weight loss, and longer-term sequelae that include growth stunting in children who had no obvious symptoms and a high frequency of postinfectious irritable bowel syndrome (IBS).

Metronidazole for Helicobacter pylori eradication therapy among children and adolescents in Japan: Overcoming controversies and concerns

BACKGROUND

Metronidazole is an antiprotozoal drug used to treat a broad spectrum of infectious diseases, including Helicobacter pylori (H pylori) infections. In Japan, metronidazole is approved for the eradication therapy of H pylori as a second-line regimen among adults, but it has not yet been approved for use among children and adolescents.

MATERIALS AND METHODS

To perform this narrative review, we searched the relevant literature on important events in the history of the use of metronidazole, its mechanisms of action, its efficacy, and the adverse effects reported in clinical trials or cohort studies in Japan.

RESULTS

At present, metronidazole resistance has not been a serious issue in Japan in large part due to its restricted use. Emerging evidence from randomized controlled trials demonstrates higher eradication rates for metronidazole than for clarithromycin, supporting its use in both first-line and second-line eradication therapies. Among the reported adverse effects, there has been lingering concern over the potential carcinogenicity of metronidazole in humans. However, the possibility of an increased cancer risk is not limited to metronidazole; the long-term use of antibiotics has been linked to increased risk for some site-specific cancers. However, recent prospective studies have suggested that short-term exposure to antibiotics is not associated with an increased cancer risk.

CONCLUSION

Sensible use of metronidazole backed by research evidence could maximize the benefits associated with H pylori eradication in Japan.

Usefulness of vonoprazan, a potassium ion-competitive acid blocker, for primary eradication of Helicobacter pylori

AIM

To investigate usefulness of triple therapy with vonoprazan, a potassium ion-competitive acid blocker and antibiotics, for Helicobacter pylori (H. pylori) eradication.

METHODS

The H. pylori eradication rate was examined in 2507 patients (2055 undergoing primary eradication and 452 undergoing secondary eradication, excluding patients with subtotal gastrectomy) at the Japanese Red Cross Kyoto Daiichi Hospital from March 2013 to September 2015. For patients treated from March 2013 to February 2015, a proton pump inhibitor (PPI) was used to reduce acid secretion, while vonoprazan was used after March 2015. The success rates of the 2 regimens (PPI + amoxicillin + clarithromycin/metronidazole, or vonoprazan + amoxicillin + clarithromycin/metronidazole) were compared.

RESULTS

The success rate of primary H. pylori eradication was significantly higher in the vonoprazan group. When stratified by the underlying disease, a significant increase of the H. pylori eradication rate was observed in patients with chronic gastritis. A significantly lower H. pylori eradication rate was observed in younger patients compared to older patients in the PPI group, but there was no difference according to age in the vonoprazan group. On the other hand, the success rate of secondary eradication was similar at approximately 90% in both groups.

CONCLUSION

Vonoprazan is very useful for primary eradication of H. pylori, and may become a first-line acid secretion inhibitor instead of PPIs.

Non-bismuth quadruple therapy for first-line Helicobacter pylori eradication: A randomized study in Japan

AIM: To find the way to improve the eradication rate of first-line therapy in Japanese patients.

METHODS: We prospectively compared the effectiveness of 7-d quadruple therapy to standard 7 d triple therapy in Japanese patients infected with Helicobacter pylori (H. pylori). One hundred and nineteen patients were randomly assigned to receive 7-d non-bismuth quadruple therapy with lansoprazole, amoxicillin, clarithromycin and metronidazole (LACM7) or 7-d triple therapy with lansoprazole, amoxicillin and clarithromycin (LAC7). After three months, H. pylori status was analyzed by ¹³C-urea breath test. Incidence rates of adverse events were evaluated by use of questionnaires.

RESULTS: By intention-to-treat (ITT) analysis, the eradication rate in the LACM7 group was 94.9%, which was significantly higher than the LAC7 group (68.3%, P < 0.001). Per protocol analysis also showed a significantly higher eradication rate in the LACM7 group (98.3%) than the LAC7 group (73.2%, P < 0.001). Nevertheless, the incidence of serious adverse events did not differ between the two groups (RR: 1.10, 95% CI: 0.70-1.73, P = 0.67).

CONCLUSION: Seven day non-bismuth quadruple therapy (LACM7) was superior to standard 7-d triple therapy (LAC7) for first-line eradication.

[Marked efficacy of metronidazole for the intestinal pseudoobstruction associated with systemic sclerosis]

In May 2009, a 57-year-old woman who had rheumatoid arthritis since 9 years was admitted to our hospital for dyspnea due to interstitial pneumonia (IP). On admission, she exhibited proximal scleroderma, finger edema, Raynaud's phenomenon, digital pitting scars, ankyloglossia, and esophageal dysmotility. The patient was diagnosed as having systemic sclerosis (SSc), according to the American College of Rheumatology criteria. After initiation of high-dose corticosteroid therapy, gradual amelioration of IP was observed. However, the patient complained of abdominal fullness. Computed tomography and intestine series findings revealed significant dilatation of the small intestine due to intra-abdominal free air and pneumatosis cystoides intestinalis but no mechanical obstruction, leading to a diagnosis of SSc with pseudo-obstruction. The patient underwent decompression with a long intestinal tube, which led to improvement in her symptoms. Although erythromycin (EM) and some prokinetic agents were administered, abdominal involvement recurred several days after resumption of oral ingestion. Therefore, we changed the antibiotic from EM to metronidazole (750 mg/day). Her manifestations were promptly ameliorated by metronidazole therapy in 4 days and did not recur. Metronidazole is an antibiotic used to treat intra-abdominal anaerobic bacterial infections and is also commonly used in preoperative treatment for colorectal surgery. In conclusion, we report a case where SSc-associated pseudo-obstruction was successfully managed by metronidazole therapy.

Antibiotic chemotherapy during pregnancy and lactation period: aspects for consideration

BACKGROUND

Infections during gestation, delivery and the postnatal period can jeopardise not only the mother, but also the child. Along with chromosomal abnormalities and immunological diseases, infection in early pregnancy represents the most important reason for abortion. During the second and third trimester, infections are the principal cause for preterm labour, premature membrane rupture, premature delivery and the resultant complications in the newborn child. Many pregnant women are very cautious about taking antibiotics due to primarily potentially detrimental effects on the unborn child. However, there are no contraindications for antibiotic treatment during pregnancy in the event of a serious infectious disease of the mother.

MATERIALS AND METHODS

In this review the indications and contraindications of the administration of antibiotics during pregnancy are being reviewed.

RESULTS

Penicillins are a first-line antibiotic treatment during pregnancy, with the exception of cases in which there is a maternal allergy to penicillin. Cephalosporins are another first-line antibiotic used during pregnancy. In principle, more commonly used cephalosporins should be given priority. Owing to associated nephrotoxicity and ototoxicity, aminoglycosides should not be prescribed at any time during pregnancy. Systematic use of aminoglycosides should be considered solely in the event of life-threatening infections with gram-negative pathogens and/or treatment failure of recommended antibiotics during pregnancy. The use of metronidazole is also permitted during pregnancy, provided the indications for its use have been strictly verified. Lincosamides should be used only if penicillins, cephalosporins and erythromycin have failed to eradicate infection. Sulfonamides, trimethoprim and cotrimoxazole are second-line agents for the use during pregnancy. Tetracyclines should not be administered to pregnant women after the fifth week of pregnancy, and are deemed contraindicated. As a precautionary measure, gyrase inhibitors are also contraindicated for pregnant women, children and young adolescents.

CONCLUSION

On the basis of our current state of knowledge, the vast majority of antibiotics do not cause serious harm to the unborn child if used properly and at the appropriate doses during pregnancy. The treatment with an antibiotic that is contraindicated does not justify termination of pregnancy. However, ultimately no medicine, including antibiotics, can be described as absolutely safe.

Guidelines for the management of Helicobacter pylori infection in Japan: 2009 revised edition

BACKGROUND

Over the past few years, the profile of Helicobacter pylori infection has changed in Japan. In particular, the relationship between H. pylori and gastric cancer has been demonstrated more clearly. Accordingly, the committee of the Japanese Society for Helicobacter Research has revised the guidelines for diagnosis and treatment of H. pylori infection in Japan.

MATERIALS AND METHODS

Four meetings of guidelines preparation committee were held from July 2007 to December 2008. In the new guidelines, recommendations for treatment have been classified into five grades according to the Minds Recommendation Grades, while the level of evidence has been classified into six grades. The Japanese national health insurance system was not taken into consideration when preparing these guidelines.

RESULTS

Helicobacter pylori eradication therapy achieved a Grade A recommendation, being useful for the treatment of gastric or duodenal ulcer, for the treatment and prevention of H. pylori-associated diseases such as gastric cancer, and for inhibiting the spread of H. pylori infection. Levels of evidence were determined for each disease associated with H. pylori infection. For the diagnosis of H. pylori infection, measurement of H. pylori antigen in the feces was added to the tests not requiring biopsy. One week of proton-pump inhibitor-based triple therapy (including amoxicillin and metronidazole) was recommended as second-line therapy after failure of first-line eradication therapy.

CONCLUSION

The revised Japanese guidelines for H. pylori are based on scientific evidence and avoid the administrative restraints that applied to earlier versions.

Epidemiologic evaluation of pharmaceuticals with limited evidence of carcinogenicity

Thorough review by the International Agency for Research on Cancer (IARC) has resulted in classifying many substances, including pharmaceuticals, as probably or possibly carcinogenic to humans, based on experiments on animals or limited data on humans. We evaluated 9 such pharmaceuticals for evidence of carcinogenicity in patients receiving them in a large medical care program with automated pharmacy records and a cancer registry. Nested case-control analyses were performed in a cohort of 6.5 million subscribers with up to 12 years of follow-up, focusing on cancer sites suggested by previous evidence and other sites with odds ratio of at least 1.50, p < 0.01 and some evidence of dose-response. Unmeasured confounding was estimated in sensitivity analyses. We found some supportive evidence for carcinogenicity of griseofulvin, metronidazole and phenytoin and for the known carcinogen, cyclophosphamide, which was added for validation of our data and analyses. Findings for chloramphenicol, iron-dextran complex, phenoxybenzamine and phenobarbital were essentially non-contributory. Confounding by cigarette smoking and prior thyroid disease could account, respectively, for associations of oxazepam with lung cancer and propylthiouracil with thyroid cancer. Although not definitive, these findings should be considered in the evaluations of these pharmaceuticals.

Dual therapy with high doses of rabeprazole and amoxicillin versus triple therapy with rabeprazole, amoxicillin, and metronidazole as a rescue regimen for Helicobacter pylori infection after the standard triple therapy

BACKGROUNDS AND AIMS

Development of safe and effective rescue regimens for eradication failure of Helicobacter pylori infection by standard regimens is an urgent task. We designed the prospective study to compare the efficacy of two rescue regimens after eradication failure by the standard triple therapy.

METHODS

One hundred and thirty-two patients in whom eradication of H. pylori infection failed initial triple therapy with lansoprazole 30 mg b.i.d, amoxicillin 750 mg b.i.d. and clarithromycin 400 mg b.i.d. for 1 week were randomized to either the 1-week triple therapy with rabeprazole 10 mg b.i.d., amoxicillin 750 mg b.i.d., and metronidazole 250 mg b.i.d. (RAM) or the 2-week dual therapy with rabeprazole 10 mg q.i.d. and amoxicillin 500 mg q.i.d. (RA). Eradication of H. pylori was judged by (13)C-urea breath test 1 month later.

RESULTS

The intention-to-treat and per-protocol-based eradication rates were 92.4% (95% CI: 83.2-97.5) and 95.3% (95% CI: 86.9-99.0) for the RAM therapy and 90.9% (95% CI: 81.2-96.6) and 93.8% (95% CI: 84.8-98.3), respectively, for the RA therapy (P > 0.2 for both). No clinically recognizable adverse events were observed with either regimen.

CONCLUSION

RA as well as RAM therapy are safe and effective rescue regimens for H. pylori infection after eradication failure by the standard triple therapy.

Efficacy of metronidazole as second-line drug for the treatment of Helicobacter pylori Infection in the Japanese population: a multicenter study in the Tokyo Metropolitan Area

BACKGROUND

With the increase in the frequency of clarithromycin-resistant Helicobacter pylori (H. pylori), there is rising concern about the decline of the eradication rate of this infection following treatment. The Tokyo Hp Study Group examined the eradication rate in response to a second-line regimen consisting of proton pump inhibitor (PPI), amoxicillin, and metronidazole by conducting a multicenter study in the Tokyo Metropolitan Area.

MATERIALS AND METHODS

Two hundred and twenty-eight patients with H. pylori infection, in whom the first-line therapy with a PPI, amoxicillin, and clarithromycin administered for 1 week had failed to eradicate the infection, were enrolled in this study. These cases were randomly assigned to one of the two second-line regimens containing metronidazole (PPI/AM500 or PPI/AM750) administered for 1 week. 13C-urea breath test was performed as a diagnostic method test for H. pylori infection not earlier than 8 weeks after the second-line therapy.

RESULTS

Intention-to-treat (ITT) and per-protocol (PP) analyses revealed an eradication rate of 87.6 and 90.6%, respectively, following PPI/AM500 treatment, and 86.9 and 88.6%, respectively, following PPI/AM750 treatment. Neither analysis revealed any significant difference in the eradication rate between PPI/AM500 and PPI/AM750 (p = .876 and .621, respectively). According to ITT and PP analyses, the eradication rates following treatment with PPI/AM500 were 85.2 and 88.5% with the use of lansoprazole, 62.5 and 62.5% with the use of omeprazole, and 93.2 and 96.5% with the use of rabeprazole, respectively. There was a significant difference in the eradication rates between PPI (omeprazole)/AM500 and PPI (rabeprazole)/AM500. In the case of PPI/AM750, the corresponding eradication rates were 84.8 and 87.0% with the use of lansoprazole, 92.9 and 92.9% with the use of omeprazole, and 92.9 and 92.9% with the use of rabeprazole, respectively. There were no significant differences in the eradication rates obtained with the use of the three PPIs.

CONCLUSIONS

Both PPI/AM500 and PPI/AM750 administered for 1 week appeared to be highly effective second-line regimens for the treatment of H. pylori infection in Japanese patients. From the viewpoint of adverse events, PPI/AM500 appeared to be safe compared with PPI/AM750.

Influence of CYP2C19 pharmacogenetic polymorphism on proton pump inhibitor-based therapies

Proton pump inhibitors (PPIs), such as omeprazole, lansoprazole, rabeprazole, esomeprazole, and pantoprazole, are mainly metabolized by CYP2C19 in the liver. There are genetically determined differences in the activity of this enzyme. The genotypes of CYP2C19 are classified into the three groups, rapid extensive metabolizer (RM), intermediate metabolizer (IM), and poor metabolizer (PM). The pharmacokinetics and pharmacodynamics of PPIs depend on CYP2C19 genotype status. Plasma PPI levels and intragastric pHs during PPI treatment in the RM group are lowest, those in the IM group come next, and those in the PM group are highest of the three groups. These CYP2C19 genotype-dependent differences in pharmacokinetics and pharmacodynamics of PPIs influence the cure rates for the gastro-esophageal reflux disease and H. pylori infection by PPI-based therapies. For the better PPI-based treatment, doses and dosing schemes of PPIs should be optimized based on CYP2C19 genotype status.

Pharmacogenomics of proton pump inhibitors

Proton pump inhibitors (PPIs), such as omeprazole, lansoprazole, rabeprazole, esomeprazole, and pantoprazole, are metabolized by cytochrome P450 isoenzyme 2C19 (CYP2C19) in the liver. There are genetic differences that affect the activity of this enzyme. The genotypes of CYP2C19 are classified into three groups: homozygous extensive metabolizer (homEM), heterozygous extensive metabolizer (hetEM), and poor metabolizer (PM). The pharmacokinetics and pharmacodynamics of PPIs differ among the different CYP2C19 genotype groups. Plasma PPI and intragastric pH levels during PPI treatment are the lowest in the homEM group and the highest in the PM group. These CYP2C19 genotype-dependent differences in pharmacokinetics and pharmacodynamics of PPIs are reflected in the cure rates for gastroesophageal reflux disease and Helicobacter pylori infection with PPI-based therapies. The CYP2C19 genotyping test is a useful tool for deciding on the optimal treatment regimen using a PPI, including a dual (PPI plus antibiotic) or a triple (PPI plus two antibiotics) therapy.

Impact of clarithromycin resistance and CYP2C19 genetic polymorphism on treatment efficacy of Helicobacter pylori infection with lansoprazole- or rabeprazole-based triple therapy in Japan

OBJECTIVE

Helicobacter pylori treatment failure is thought to be due mainly to polymorphic cytochrome P450 2C19 (CPY2C19) genetic polymorphism, associated with proton pump inhibitor metabolism, and antimicrobial susceptibility. This report has ascertained which was more important, CPY2C19 polymorphism or antimicrobial susceptibility, when using 1-week lansoprazole-based or rabeprazole-based triple therapy in Japan.

DESIGN

An open, randomized, parallel group study.

SETTING

One hundred and forty-five subjects with H. pylori-positive gastritis or peptic ulcers were randomly assigned to receive 30 mg lansoprazole twice daily (LAC group), 10 mg rabeprazole twice daily (RAC20 group), or 20 mg rabeprazole twice daily (RAC40 group), with 1000 mg amoxicillin twice daily and 400 mg clarithromycin twice daily for 1 week. Antimicrobial resistance testing was performed by E-test. More than 4 weeks after completion of treatment, H. pylori status was assessed by 13C-urea breath test, histology, and culture.

RESULTS

Cure rates expressed as intention-to-treat and per-protocol analyses, respectively, were 79.6 and 83.0% with LAC, 85.4 and 89.1% with RAC20, and 83.3 and 88.9% with RAC40. In the case of clarithromycin-sensitive strains, the cure rates were more than 97%, regardless of CPY2C19 polymorphism. However, treatment succeeded in only one out of 16 clarithromycin-resistant strains.

CONCLUSIONS

The key to successful eradication of H. pylori, using lansoprazole or rabeprazole with clarithromycin and amoxicillin, is clarithromycin susceptibility, not CPY2C19 polymorphism.

Efficacy of triple therapy comprising rabeprazole, amoxicillin and metronidazole for second-line Helicobacter pylori eradication in Japan, and the influence of metronidazole resistance

BACKGROUND

The widespread use of eradication therapy for Helicobacter pylori in Japan has led to an increase in antibiotic-resistant strains and the problem of re-treatment in cases of eradication failure.

AIM

To perform drug sensitivity testing for metronidazole in 92 H. pylori-positive patients who had failed eradication treatment with first-line triple therapy, consisting of a proton pump inhibitor, amoxicillin and clarithromycin, and were administered metronidazole-containing second-line therapy.

METHODS

Second-line eradication therapy, consisting of rabeprazole (20 mg b.d.), amoxicillin (750 mg b.d.) and metronidazole (250 mg b.d.), was administered for 1 week and the eradication rates and influence of metronidazole resistance were determined.

RESULTS

The eradication rates for rabeprazole-amoxicillin-metronidazole were 88% (81/92) using intention-to-treat analysis and 91% (81/89) using per protocol analysis. The eradication rates were 97% (61/63) for metronidazole-sensitive strains and 82% (18/22) for metronidazole-resistant strains.

CONCLUSIONS

As second-line H. pylori eradication treatment in Japan, rabeprazole-amoxicillin-metronidazole triple therapy is effective, even with metronidazole-resistant strains.

Effects of genotypic differences in CYP2C19 status on cure rates for Helicobacter pylori infection by dual therapy with rabeprazole plus amoxicillin

Rabeprazole is a potent proton pump inhibitor and is mainly reduced to thioether rabeprazole by a non-enzymatic pathway and partially metabolized to demethylated rabeprazole by CYP2C19 in the liver. We intended to determine a cure rate for Helicobacter pylori infection by dual rabeprazole/amoxicillin therapy in relation to CYP2C19 genotype status prospectively. Ninety-seven patients with gastritis and H. pylori infection completed the dual therapy with 10 mg of rabeprazole bid and 500 mg of amoxicillin tid for 2 weeks. At 1 month after treatment, cure of H. pylori infection was assessed on the basis of histology, a rapid urease test, culture, polymerase chain reaction (PCR), and 13C-urea breath test. CYP2C19 genotype status was determined by a PCR-restriction fragment length polymorphism method. Of the 97 patients, 33 were homozygous extensive metabolizers (homEM), 48 were heterozygous extensive metabolizers (hetEM), and 16 were poor metabolizers (PM). Cure of H. pylori infection was achieved in 79 of the 97 patients (81.4%, 95%CI = 71.9-88.7). Significant differences in cure rates among the homEM, hetEM, and PM groups were observed; 60.6% (95%CI = 42.1-77.3), 91.7% (95%CI = 80.0-97.7), and 93.8% (95%CI = 69.8-99.8), respectively (P = 0.0007). Twelve patients without cure after initial treatment (10 homEMs and 2 hetEMs) were successfully retreated with rabeprazole 10 mg q.i.d. and amoxicillin 500 mg q.i.d. for 2 weeks. The cure rates for H. pylori infection by dual rabeprazole/amoxicillin therapy depended on the CYP2C19 genotype status. This dual therapy appears to be effective for hetEM and PM patients. However, high dose dual rabeprazole/amoxicillin therapy was effective even for homEM patients. Therefore, the genotyping test of CYP2C19 appears to be a clinically useful tool for the optimal dual treatment with rabeprazole plus amoxicillin.

Treatment of giardiasis

Giardia lamblia is both the most common intestinal parasite in the United States and a frequent cause of diarrheal illness throughout the world. In spite of its recognition as an important human pathogen, there have been relatively few agents used in therapy. This paper discusses each class of drugs used in treatment, along with their mechanism of action, in vitro and clinical efficacy, and side effects and contraindications. Recommendations are made for the preferred treatment in different clinical situations. The greatest clinical experience is with the nitroimidazole drugs, i.e., metronidazole, tinidazole, and ornidazole, which are highly effective. A 5- to 7-day course of metronidazole can be expected to cure over 90% of individuals, and a single dose of tinidazole or ornidazole will cure a similar number. Quinacrine, which is no longer produced in the United States, has excellent efficacy but may be poorly tolerated, especially in children. Furazolidone is an effective alternative but must be administered four times a day for 7 to 10 days. Paromomycin may be used during early pregnancy, because it is not systematically absorbed, but it is not always effective. Patients who have resistant infection can usually be cured by a prolonged course of treatment with a combination of a nitroimidazole with quinacrine.

Effects of clarithromycin on the metabolism of omeprazole in relation to CYP2C19 genotype status in humans

BACKGROUND AND PURPOSE

A triple therapy with omeprazole, amoxicillin (INN, amoxicilline), and clarithromycin is widely used for the eradication of Helicobacter pylori. Omeprazole and clarithromycin are metabolized by CYP2C19 and CYP3A4. This study aimed to elucidate whether clarithromycin affects the metabolism of omeprazole.

METHODS

After administration of placebo or 400 mg clarithromycin twice a day for 3 days, 20 mg omeprazole and placebo or 400 mg clarithromycin were administered to 21 healthy volunteers. Plasma concentrations of omeprazole and clarithromycin and their metabolites were determined before and 1, 2, 3, 5, 7, 10, and 24 hours after dosing. CYP2C19 genotype status was determined by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Subjects were classified into three groups on the basis of PCR-RFLP analyses for CYP2C19: homozygous extensive metabolizer group (n = 6), heterozygous extensive metabolizer group (n = 11), and poor metabolizer group (n = 4). Mean area under the plasma concentration-time curves from 0 to 24 hours (AUC) of omeprazole in the homozygous extensive metabolizer, heterozygous extensive metabolizer, and poor metabolizer groups were significantly increased by clarithromycin from 383.9 to 813.1, from 1001.9 to 2110.4, and from 5589.7 to 13098.6 ng x h/mL, respectively. There were significant differences in the mean AUC values of clarithromycin among the three groups.

CONCLUSION

Clarithromycin inhibits the metabolism of omeprazole. Drug interaction between clarithromycin and omeprazole may underlie high eradication rates achieved by triple therapy with omeprazole, amoxicillin, and clarithromycin.

Prenatal exposure to metronidazole and risk of childhood cancer: a retrospective cohort study of children younger than 5 years

BACKGROUND

To evaluate the role of in utero exposure to metronidazole (a carcinogen in some animal models) and the risk of subsequent cancer, the authors conducted a retrospective cohort study of childhood cancer.

METHODS

The cohort included 328,846 children younger than 5 years born to women enrolled in Tennessee Medicaid at any time between the last menstrual period (LMP) and the date of delivery. The cohort was identified by linking files of Tennessee Medicaid mothers ages 15-44 years and children and the children's birth and death certificates for the period January 1, 1975 through December 31, 1992. Exposure data were obtained from Medicaid pharmacy records and exposure was defined as filling a metronidazole prescription that had at least a day's supply between the 30 days prior to the LMP and the date of delivery. Study cases were cohort children diagnosed with a first primary cancer before age 5 years, identified by linking the cohort with a statewide childhood cancer database for the study period.

RESULTS

Cohort members contributed 1,172,696 person-years of follow-up for analysis, with children exposed (8.1%) and not exposed (91.9%) in utero to metronidazole contributing 79,716 and 1,092,980 person-years, respectively. Of 952 children younger than 5 years in the statewide cancer database, 175 met study eligibility criteria. Of these, 42 had leukemia, 30 had central nervous system (CNS) tumors, 28 had neuroblastoma, and 75 had other cancers. Using Poisson regression modeling, children exposed to metronidazole in utero had no significant increase in adjusted relative risk (RR) for all cancers (RR: 0.81; 95% confidence interval [95% CI], 0.41-1.59), leukemia (no exposed case), CNS tumors (RR: 1.23; 95% CI, 0.29-5.21), neuroblastomas (RR: 2.60; 95% CI, 0.89-7.59), and other cancers (RR: 0.57; 95% CI, 0.18-1.82).

CONCLUSIONS

The authors conclude that although there was no increase in risk for all cancers associated with in utero exposure to metronidazole, the observed increased risk for neuroblastomas, although not significant, requires further evaluation.

Serum organochlorine pesticide levels in patients with colorectal cancer in Egypt

The widespread use of pesticides in Egypt, the high incidence of colorectal cancer in Egyptian children and young adults, and the published U.S. case reports in which pesticides have been connected with colorectal cancer led the authors to investigate the possible association between organochlorines and colorectal cancer. The authors conducted a pilot study to describe serum organochlorine levels among 31 Egyptian colorectal patients and 17 controls. High levels and large interindividual variability of p,p'-dichloro-diphenyldicholoroethylene (DDE), dichloro-diphenyl-trichloroanthane (DDT), beta-hexachlorocyclohexane (beta-HCH), and hexachlorobenzene (HCB) levels were found among most subjects, especially those from rural areas. Farming and aging were each associated positively with high serum organochlorines. Colorectal cancer patients had higher serum organochlorines levels than controls. The high levels of organochlorines reported and their relation to age, residence, occupation, and disease status justify further study of the possible association between organochlorine pesticides and colorectal cancer in a larger population in Egypt.

Antibiotic use in pregnancy

With a few notable exceptions, most antibiotics can be used with relative safety during pregnancy. Moreover, none of the antibiotics to date has been shown to be teratogenic, although tetracycline may cause yellow-brown discoloration of the deciduous teeth (a fetal effect). Thus, antibiotics should not be withheld from the pregnant woman, especially when indicated for serious, life-threatening infections.

Clindamycin and metronidazole

Metronidazole is a bactericidal antibiotic with strong activity against most anaerobes and certain parasites. The drug has excellent bioavailability and good penetration in most tissues, including the cerebrospinal fluid and brain abscess contents. It is usually well tolerated with few side effects. With a few exceptions, the percentage of anaerobes, including B. fragilis group, that are resistant to metronidazole remains low. Metronidazole has been used extensively in clinical practice for years, and its uses have expanded. Its exact role in the management of Crohn's disease and entities related to H. pylori is evolving.

Bacterial vaginosis: efficacy and safety of intravaginal metronidazole treatment

OBJECTIVE

We evaluated the effectiveness and safety of intravaginal metronidazole in the treatment of bacterial vaginosis. Demographic data, Gram stain score, and individual clinical diagnostic criteria for bacterial vaginosis were evaluated for association with therapeutic outcome.

METHODS

According to accepted diagnostic criteria and blinded Gram stain scoring for quality control, a multicenter, prospective, double-blinded trial of patients randomized to either 0.75% metronidazole gel 5 gm twice daily for 5 days or placebo was undertaken. Therapeutic response after completion of treatment was evaluated by examination at 4 to 16 days and again at 28 to 32 days for patients initially cured.

RESULTS

After metronidazole treatment, 38 (78%) of 49 patients were cured initially, compared with 11 (27%) of 41 placebo recipients (p < 0.001). One month after treatment 31 (91%) of 34 in the group initially cured by metronidazole remained cured. Side effects were uncommon and mild. Significant intercenter differences were noted for vaginal discharge assessment but not for other diagnostic criteria. Among patients cured initially with metronidazole, mean Gram stain score was 0.58 among those in whom cure was maintained versus 2.33 for those in whom recurrent bacterial vaginosis developed 1 month after treatment (p = 0.03). Curative metronidazole treatment was found initially in 4 (100%) of 4 patients with sperm present on gram stain compared with 34 (76%) of 45 with sperm absent (p = 0.56) and in 6 (100%) of 6 and 25 (89%) of 28, respectively, at the final visit (p = 1.0).

CONCLUSIONS

Intravaginal metronidazole is effective, safe, well-tolerated, durable therapy for bacterial vaginosis. Characterization of vaginal discharge appears to be the most variable among the diagnostic criteria for bacterial vaginosis. Gram stain score may be able to identify patients cured early after therapy who are at risk for later recurrence. Exposure to semen does not appear to affect efficacy of intravaginal metronidazole.

The role of metronidazole in the treatment of periodontal diseases

This article discusses the ability of metronidazole to improve periodontal health. Review of the drug's pharmacology and potential side effects indicate that it poses little threat to humans of inducing acute toxicity, mutagenesis, or cancer if used according to recommended dosing regimens. Studies addressing metronidazole utilization in a variety of clinical conditions demonstrate that its routine use does not enhance root planing. However, adjunctive antibiotic therapy may be advantageous in the treatment of sites where effective root planing is precluded due to deep pockets or when anaerobic periodontal infections do not respond to conventional therapy.

The biology of Giardia spp

Gardia spp. are flagellated protozoans that parasitize the small intestines of mammals, birds, reptiles, and amphibians. The infectious cysts begin excysting in the acidic environment of the stomach and become trophozoites (the vegetative form). The trophozoites attach to the intestinal mucosa through the suction generated by a ventral disk and cause diarrhea and malabsorption by mechanisms that are not well understood. Giardia spp. have a number of unique features, including a predominantly anaerobic metabolism, complete dependence on salvage of exogenous nucleotides, a limited ability to synthesize and degrade carbohydrates and lipids, and two nuclei that are equal by all criteria that have been tested. The small size and unique sequence of G. lamblia rRNA molecules have led to the proposal that Giardia is the most primitive eukaryotic organism. Three Giardia spp. have been identified by light lamblia, G. muris, and G. agilis, but electron microscopy has allowed further species to be described within the G. lamblia group, some of which have been substantiated by differences in the rDNA. Animal models and human infections have led to the conclusion that intestinal infection is controlled primarily through the humoral immune system (T-cell dependent in the mouse model). A major immunogenic cysteine-rich surface antigen is able to vary in vitro and in vivo in the course of an infection and may provide a means of evading the host immune response or perhaps a means of adapting to different intestinal environments.

Use of the SEER Cancer Registry for technology assessment

The Surveillance, Epidemiology, and End Results (SEER) cancer registry contributed to technology assessment by providing population-based samples for detailed case-control studies, by serving as the control group in comparisons with various experimental groups, by allowing an assessment of selection bias in clinical trials, and by facilitating evaluations of classification and coding systems.

Industrial risk factors for colorectal cancer

Colorectal cancer is the second most common malignancy in the United States, and its incidence rates have sharply increased recently, especially in males. Industrial exposures, both occupational and environmental, are important colorectal cancer risk factors that are generally unrecognized by clinicians. Migration studies have documented that colorectal cancer is strongly associated with environmental risk factors. The causal role of occupational exposures is evidenced by a substantial literature associating specific work practices with increased colorectal cancer risks. Industrially related environmental exposures, including polluted drinking water and ionizing radiation, have also been associated with excess risks. Currently, there is a tendency to attribute colorectal cancer, largely or exclusively, to dietary and other lifestyle factors, thus neglecting these industrially related effects. Concerted efforts are needed to recognize the causal role of industrial risk factors and to encourage government and industry to reduce carcinogenic exposures. Furthermore, cost-effective screening programs for high-risk population groups are critically needed to further reduce deaths from colorectal cancer.

Epidemiological screening for potentially carcinogenic drugs

This paper describes a unique program for the systematic screening of commonly used prescription drugs for possible carcinogenic effects, by following up a large cohort of patients with computer-stored pharmacy data for incidence of cancer. Among the most interesting findings in recent analyses are an association of several antibiotics with subsequent lung cancer, and negative associations of prescribed vitamin E and diazepam with certain cancers. Analyses of additional data do not clearly indicate that these represent causal relationships to the drugs themselves. Also of interest is our continuing negative evidence regarding reserpine and metronidazole. The planned computerization of all pharmacies in our medical care program now serving over 2.2 million subscribers, should greatly increase our drug surveillance capabilities.