Metformin-Cimetidine Drug Interaction and Risk of Lactic Acidosis in Renal Failure: A Pharmacovigilance-Pharmacokinetic Appraisal.

OBJECTIVE: This study aimed to evaluate lactic acidosis (LA) risk when using metformin combined with histamine H2 receptor inhibitors (H2RI) in patients with renal failure (RF). RESEARCH DESIGN AND METHODS: This study analyzed FDA Adverse Event Reporting System data (2012Q4 to 2022Q4) to characterize reports of LA associated with metformin alone or combined with H2RI. Using a disproportionality approach, LA risk signal in the overall population and in patients with RF was assessed. A physiologically based pharmacokinetic (PBPK) model was developed to predict metformin and cimetidine pharmacokinetic changes following conventional doses of the combinations in patients with various degrees of RF. To explore its correlation with LA risk, a peak plasma metformin concentration of 3 mg/L was considered the threshold. RESULTS: Following the 2016 U.S. Food and Drug Administration metformin approval for mild-to-moderate RF, the percentage of patients with RF reporting LA associated with metformin combined with H2RI increased. Disproportionality analysis showed reported LA risk signal associated with metformin and cimetidine in the overall population within the study timeframe only. Furthermore, with PBPK simulations, for metformin (1,000 mg b.i.d.) with cimetidine (300 mg q.i.d. or 400 mg b.i.d.) in stage 1 of chronic kidney disease, metformin (1,000 mg b.i.d.) with cimetidine (300 mg q.i.d. or 400 mg b.i.d. or 800 mg q.d.) in stage 2, and most combinations in stage 3, the peak plasma metformin concentrations exceeded the 3 mg/L threshold. CONCLUSIONS: Metformin combined with cimetidine at conventional doses may cause LA in patients with mild-to-moderate RF.

Acute tubulointerstitial nephritis associated with antineutrophil cytoplasmic antibody following cimetidine treatment: a case report.

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis usually induces rapidly progressive glomerulonephritis, including pauci-immune necrotizing crescentic glomerulonephritis. Acute tubulointerstitial nephritis (ATIN), which is often drug-induced, is a frequent cause of kidney injury. However, ATIN associated with ANCA without any glomerular lesions has been rarely reported, and drug-induced ATIN associated with ANCA is not well recognized. Here we present a case of an older woman with ATIN associated with myeloperoxidase-ANCA (MPO-ANCA) following cimetidine treatment. CASE PRESENTATION: A 70-year-old woman was admitted to our hospital due to acute kidney injury and mild proteinuria. She had a one-year history of chronic thyroiditis and dyslipidemia, for which she was taking levothyroxine sodium and atorvastatin, respectively. Two weeks before admission she had started cimetidine, methylmethionine sulfonium chloride, and itopride hydrochloride for gastric discomfort persistent since a month. She had experienced fatigue for two weeks and later appetite loss. The patient demonstrated a positive titer for MPO-ANCA (192 IU/mL) and a positive drug-induced lymphocyte stimulation test for cimetidine. She underwent two kidney biopsies that revealed ATIN without any glomerular lesions. Despite discontinuation of cimetidine on admission, renal injury continued with the presence of high MPO-ANCA titer. Oral steroid treatment was closely related with the recovery of her renal function and disappearance of MPO-ANCA. CONCLUSIONS: In this case, ATIN presented as sustained renal insufficiency and high MPO-ANCA titer despite withdrawal of cimetidine. Therefore, we reason that the development of ANCA-associated ATIN was caused by cimetidine. Serologic follow-up with measurement of MPO-ANCA titers and renal biopsy are recommended when the clinical history is inconsistent with the relatively benign course of drug-induced ATIN.

Environmental risk assessment of metformin and its transformation product guanylurea. I. Environmental fate.

Metformin (MET) is a pharmaceutical with very high use worldwide that is excreted in unchanged form, leading to concern about potential aquatic life impacts associated with MET, and its primary transformation product guanylurea (GUU). This study presents, in two companion papers, a risk assessment following internationally accepted guidelines of MET and GUU in surface water based on literature data, previously unpublished studies, and a new degradation test that resolves conflicting earlier results. Previous studies have shown that MET is removed during sewage treatment, primarily through transformation to GUU. In addition, measurements in WWTPs suggest that MET is not only transformed to GUU, but that GUU is further biodegraded. A prolonged inherent biodegradation test strongly suggests not only primary transformation of MET to GUU, but also subsequent full mineralization of GUU, with both degradation phases starting after a clear lag phase. MET may partition from surface water to sediment, where both transformation to GUU and in part mineralization is possible, depending on the presence of competent degrading microorganisms. In addition, MET may form non-extractable residues in sediments (12.8-73.5%). Both MET and GUU may be anaerobically degraded during sludge digestion, in soils or in sediments. Bioconcentration factor (BCF) values in crops and most plants are close to 1 suggesting low bioaccumulation potential, moreover, at least some plants can metabolize MET to GUU; however, in aquatic plants higher BCFs were found, up to 53. Similarly, neither MET nor GUU are expected to bioaccumulate in fish based on estimated values of BCFs ≤3.16.

Miscellaneous Drugs and Male Reproduction.

In addition to main categories of medications believed to have negative impacts on male reproduction, there are a number of miscellaneous drugs with some evidence for such adverse reactions. Because of its widespread use and over-the-counter availability, the H2 receptor antagonist cimetidine is most concerning. As a competitive antagonist at androgen receptors, it can impact the HPG axis and semen quality. In this chapter, we review the studies of this drug and other histamine H2 receptor antagonists in men and experimental species. Several other medications are concerning and the evidence for negative effects on reproduction are covered: colchicine, domperidone, hydroxyurea, metformin, metoclopramide, mifepristone, retinoids, and statins.

Chloramphenicol significantly affects the pharmacokinetics of oral methadone in Greyhound dogs.

OBJECTIVE: To assess the effects of cytochrome P450 (CYP) inhibitors (ketoconazole, chloramphenicol, trimethoprim, fluoxetine, cimetidine and medetomidine) in various combinations on the pharmacokinetics of oral methadone in Greyhound dogs to determine the specific effects of the different inhibitors and if a clinically relevant interaction occurs. STUDY DESIGN: Non-randomized, sequential design. ANIMALS: Six healthy Greyhound dogs (three male, three female). METHODS: Canine CYP inhibitors (ketoconazole, chloramphenicol, trimethoprim, fluoxetine, cimetidine and medetomidine) were administered in varying combinations prior to the administration of oral methadone. Plasma was obtained from each dog to enable the determination of methadone and CYP inhibitor drug concentrations using liquid chromatography with either mass spectrometry or ultraviolet detection. RESULTS: Significant increases in the area under the curve (AUC) and maximum plasma concentrations (CMAX ) of methadone occurred in all groups administered chloramphenicol. The AUC (6 hours ng mL(-1)) and CMAX (6 ng mL(-1)) of methadone significantly increased to 541 hours ng mL(-1) and 47.8 ng mL(-1), respectively, when methadone was administered with chloramphenicol as a sole inhibitor. There were no significant effects of CYP inhibitors other than chloramphenicol on methadone pharmacokinetics, which suggests that chloramphenicol was primarily responsible for the pharmacokinetic interaction. CONCLUSIONS AND CLINICAL RELEVANCE: This study demonstrated significant effects of chloramphenicol on the pharmacokinetics of oral methadone. Further studies should investigate the effects of chloramphenicol on methadone pharmacokinetics in multiple dog breeds and examine whether oral methadone would be an effective analgesic in dogs. In addition, the safety of chloramphenicol and its effects on the pharmacokinetics of parenteral methadone warrant assessment.

Cimetidine effects on the immunosuppression induced by burn injury.

Although many studies on the immune response following burn injuries have been reported, more attention has been given to the immunosuppression mechanism and mediators that shape the process of immune suppression. Specifically, information is not available concerning the immunomodulatory effects of the drugs which are involved in the immune response restoration. In this study, we investigated the effects of Cimetidine on the modulation of immune response in patients with burn injury of 20-60%. Two groups of patients were involved in this study; the patients in one group were treated with 15 mg/kg per day of Cimetidine while the patients in the other group were treated with placebo. Peripheral blood mononuclear cell (PBMC) expressing CD3, CD4, CD8, CD19 and CD3/HLA-DR was analyzed by flow cytometry. Cell proliferation assay using H3 thymidine was performed on PBMC samples. The proliferation assay showed a significant suppression of cell proliferation rate in post-burn patients (p = 0.001). We observed a significant reduction in the lymphocyte count (p = 0.001) and frequency of CD3 (p = 0.007) and CD4 (p = 0.001) T cells in post-burn patients. Also, the frequency of CD 19+ and HLA DR+ cells was increased compare to normal donors following burn injury. Treatment with Cimetidine increased the frequency of CD8+ T cells in the patient's peripheral blood. The PBMC proliferation rate was restored following the treatment with Cimetidine (p = 0.02). Our data indicates that Cimetidine may have beneficial effects on cell mediated immunity following burn injury.

Severe lactic acidosis and acute pancreatitis associated with cimetidine in a patient with type 2 diabetes mellitus taking metformin.

An 82-year-old woman with type 2 diabetes mellitus, hypertension, and unstable angina presented with severe lactic acidosis and acute kidney injury (AKI) accompanied by acute pancreatitis. Her medical history revealed that she had taken cimetidine for two weeks while taking other medications, including metformin. Continuous veno-venous hemodiafiltration (CVVHDF) was initiated under diagnosis of lactic acidosis due to metformin and AKI caused by cimetidine-induced acute pancreatitis. In three days of CVVHDF, the levels of serum biochemical markers of lactic acidosis and AKI improved and the patient's urine output reached over 1 L/day. The pancreatitis improved over time.

Effect of cimetidine, a model drug for inhibition of the organic cation transport (OCT2/MATE1) in the kidney, on the pharmacokinetics of glycopyrronium.

OBJECTIVE: Glycopyrronium (NVA237), a novel once-daily long-acting muscarinic antagonist (LAMA), has recently been approved for maintenance treatment of COPD. This study evaluated the effect of organic cation transporter inhibition on inhaled glycopyrronium disposition using cimetidine as a probe inhibitor. METHODS: In this open-label, two-period, two-sequence, crossover study, 20 healthy subjects received two treatments. A single dose of 100 µg glycopyrronium was inhaled alone and on Day 4 of a 6-day treatment with oral cimetidine 800 mg b.i.d. Trough plasma concentrations of cimetidine were determined throughout cimetidine dosing. Plasma concentrations and urinary excretion of glycopyrronium were determined up to 72 hours post glycopyrronium dose. The primary pharmacokinetics (PK) parameters were plasma peak concentration (Cmax), AUC up to the last measured concentration (AUClast), and renal clearance (CLr) of glycopyrronium. RESULTS: Cimetidine trough concentrations indicated that PK steady state of cimetidine was reached prior to single dose inhalation of glycopyrronium. Inhalation of glycopyrronium in the presence of cimetidine resulted in an increase in total systemic exposure (AUClast) of glycopyrronium by 22% (geometric mean ratio 1.22; 90% CI: 1.12 - 1.32). This exposure increase correlated with a slight decrease of 23% in CLr (geometric mean ratio 0.77; 90% CI: 0.70 - 0.85). Cmax was not affected. Both treatments were safe and well tolerated without any deaths or severe adverse events. CONCLUSION: Based on the magnitude of the PK changes seen in this study, no relevant drug interaction is expected when glycopyrronium is co-administered with cimetidine or other inhibitors of the organic cation transport.

Cimetidine-associated patent ductus arteriosus is mediated via a cytochrome P450 mechanism independent of H2 receptor antagonism.

Persistent patency of the ductus arteriosus (PDA) is a common problem in preterm infants. The antacid cimetidine is a potent antagonist of the H2 histamine receptor but it also inhibits certain cytochrome P450 enzymes (CYPs), which may affect DA patency. We examined whether cimetidine contributes to PDA and is mediated by CYP inhibition rather than H2 blockade. Analysis of a clinical trial to prevent lung injury in premature infants revealed a significant association between cimetidine treatment and PDA. Cimetidine and ranitidine, both CYP inhibitors as well as H2 blockers, caused relaxation of the term and preterm mouse DA. CYP enzymes that are inhibited by cimetidine were expressed in DA subendothelial smooth muscle. The selective CYP3A inhibitor ketoconazole induced greater DA relaxation than cimetidine, whereas famotidine and other H2 antagonists with less CYP inhibitory effects caused less dilation. Histamine receptors were developmentally regulated and localized in DA smooth muscle. However, cimetidine caused DA relaxation in histamine-deficient mice, consistent with CYP inhibition, not H2 antagonism, as the mechanism for PDA. Oxygen-induced DA constriction was inhibited by both cimetidine and famotidine. These studies show that antacids and other compounds with CYP inhibitory properties pose a significant and previously unrecognized risk for PDA in critically ill newborn infants.

Avaliação da atividade protetora gástrica do extrato hidroalcoólico da semente de girassol em ratas / Evaluation of the gastroprotective activity of hydroalcoholic extract of sunflower seed in rats

JUSTIFICATIVA E OBJETIVOS: Avaliar a proteção gástrica do extrato hidroalcoólico da semente de girassol (EHSG) em relaçãoao estresse, ao uso de indometacina e etanol. MÉTODO: Foi realizado um estudo experimental envolvendo 90 ratas (Rattus norvegicus albinus), da linhagem Wistar, fêmeas, com peso corporal médio de 150-230 g, divididos em 18 grupos distintos os quais receberam os seguintes tratamentos: EHSG:250 mg/kg, 500 mg/kg, 1000 mg/kg e 2000 mg/kg; etanol 0,5mL; cimetidina 60 mg/kg; indometacina 20 mg/kg; água 1 mL. Os dados foram analisados utilizando o programa Grand PadPrism 5 com aplicação de testes estatísticos considerando o nível de significância de 5%. RESULTADOS: O EHSG apresenta proteção contra as lesões gástricas em ratas, nas doses de 250 e 1000 mg, tanto no modelo pelo estresse, quanto na indução por etanol e indometacina. CONCLUSÃO: Os dados obtidos no presente estudo mostram que o EHSG apresenta proteção gástrica em determinadas doses.

BACKGROUND AND OBJECTIVES: To evaluate the gastric protection hidroalcoólico extract the sunflower seed (EHSG) in relation to stress, the use of indomethacin and ethanol. METHOD: We conducted an experimental study involving 90 rats (Rattus norvegicus albinos), Wistar, females, mean body weight of 150-230 g were divided into 18 distinct groups which received the following treatments: EHSG: 250mg/kg , 500 mg/kg, 1000 mg/kg and 2000 mg/kg; 0.5 mL ethanol, cimetidine 60 mg/kg, 20 mg/kg indomethacin; 1 mL water. Data were analyzed using the GrandPad Prism 5 with application of statistical tests, the significance level of 5%. RESULTS: The EHSG has protective against gastric injury in rats at doses 250 mg and 1000, both in the model by stress, as in the induction by ethanol and indomethacin. CONCLUSION: The data obtained in this study show that has EHSG gastric protection in certain doses.

Histamine H2-receptor antagonists for urticaria.

BACKGROUND: Urticaria is a common skin disease characterised by itching weals or hives, which can occur almost anywhere on the body. There are a number of different subtypes and a range of available treatment options. There is lack of agreement on the efficacy of H2-receptor antagonists used in the treatment of urticaria. OBJECTIVES: To assess the safety and effectiveness of H2-receptor antagonists in the treatment of urticaria. SEARCH METHODS: We searched the following databases up to 7 October 2011: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library (2011, Issue 4), MEDLINE (from 2005), EMBASE (from 2007), and LILACS (from 1982). We also searched online trials registries for ongoing trials. SELECTION CRITERIA: Randomised controlled trials of H2-receptor antagonists in people with a clinical diagnosis of urticaria of any duration or of any subtype. Studies including H1-antihistamines for chronic urticaria are the topic of a separate Cochrane review; thus, they were not included in this review. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted and analysed data. MAIN RESULTS: Four studies of a relatively small size, involving 144 participants, were included in this review. A combination of ranitidine with diphenhydramine was more effective at improving the resolution of urticaria than diphenhydramine administered alone (risk ratio (RR) 1.59, 95% confidence interval (CI) 1.07 to 2.36). Although there was a similar improvement in itching, weal size, and intensity, cimetidine provided no statistically significant greater overall improvement in symptoms of urticaria when compared to diphenhydramine. However, a combination of these medications was more effective than diphenhydramine alone (RR 2.02, 95% CI 1.03 to 3.94). Adverse events were reported with several of the interventions, i.e. ranitidine and diphenhydramine, causing drowsiness and sedation, but there was no significant difference in the level of sedation from baseline with either famotidine or diphenhydramine. AUTHORS' CONCLUSIONS: The very limited evidence provided by this review was based on a few old studies of a relatively small size, which we categorised as having high to unclear risk of bias. Thus, at present, the review does not allow confident decision-making about the use of H2-receptor antagonists for urticaria. Although some of these studies have reported a measure of relief of symptoms of urticaria and rather minimal clinical improvement in some of the participants, the evidence was weak and unreliable. We have emphasised the lack of precision and limitations in the reported data where appropriate in this review.

[Drug-induced tremor]. / Medikamentös-induzierter Tremor.

Drug-induced tremor is an important differential diagnosis for tremor syndromes. In view of a constantly ageing population and increasingly frequent polypharmacotherapy, identification of potentially tremor-inducing drugs may help generating risk profiles for individual patients. Drug-induced tremor has often been seen as a complication of antipsychotic therapy, but its occurrence has also been described in response to a great diversity of compounds such as antidepressants, sympathomimetics, antiarrhythmics, antiepileptics and other drugs. The present article presents a synopsis of the most prevalent tremor-inducing drugs as well as strategies to overcome drug-induced tremor, either by replacement of the causative drug or by symptomatic therapies.

H2 blockers decrease gut mucus production and lead to barrier dysfunction in vitro.

BACKGROUND: Pneumonia and other gut-related infectious complications have been associated with the use of histamine 2 (H2) receptor antagonists such as cimetidine in critically ill patients. The mechanism(s) may include acid suppression with resultant effects on the gut flora. Other possibilities include immunologic effects and perturbation of gut barrier function. Recent work has demonstrated the importance of mucus on the gastrointestinal mucosal barrier. We studied the effect of cimetidine on mucus production and mucosal barrier function in vitro. METHODS: HT29-MTX, a mucus-producing intestinal epithelial cell line, was used. HT29-MTX cell monolayers were grown to confluence in the presence of cimetidine for 0, 3, or 6 days. Mucus production was quantified by Western Blot analysis and O-linked oligosaccharide chain release and mucin content by enzyme-linked immunosorbent assay. Fluorescein-labeled Escherichia coli (EC) or unlabeled EC were added to quantify bacterial adherence (60-min co-culture) and passage thru HT29-MTX cell monolayers (120-min co-culture), respectively. RESULTS: Cimetidine treatment decreased mucus/mucin content after 3 or 6 days of treatment. The effect was more profound after 6 days. There was nearly a 2-fold increase in passage of EC across HT29-MTX monolayers after cimetidine treatment. CONCLUSION: Cimetidine seems to contribute to gut barrier dysfunction by its effect on mucus production. This study supports the increasing clinical suspicion that routine administration of H2 blockers in critically ill patients may be ill advised.

Use of acid-suppressive drugs and risk of fracture: a meta-analysis of observational studies.

PURPOSE: Previous studies have reported inconsistent findings regarding the association between the use of acid-suppressive drugs such as proton pump inhibitors (PPIs) and histamine 2 receptor antagonists (H(2)RAs) and fracture risk. We investigated this association using meta-analysis. METHODS: We searched MEDLINE (PubMed), EMBASE, and the Cochrane Library from inception through December 2010 using common key words. We included case-control, nested case-control, and cohort studies. Two evaluators independently reviewed and selected articles. We determined pooled effect estimates by using random-effects meta-analysis, because of heterogeneity. RESULTS: Of 1,809 articles meeting our initial inclusion criteria, 5 case-control studies, 3 nested case-control studies, and 3 cohort studies were included in the final analyses. The pooled odds ratio (OR) for fracture was 1.29 (95% confidence interval [CI], 1.18-1.41) with use of PPIs and 1.10 (95% CI, 0.99-1.23) with use of H(2)RAs when compared with nonuse of the respective medications. Long-term use of PPIs increased the risk of any fracture (adjusted OR = 1.30; 95% CI, 1.15-1.48) and hip fracture risk (adjusted OR = 1.34; 95% CI, 1.09-1.66), whereas long-term H(2)RA use was not significantly associated with fracture risk. CONCLUSIONS: We found possible evidence linking PPI use to an increased risk of fracture, but no association between H(2)RA use and fracture risk. Widespread use of PPIs with the potential risk of fracture is of great importance to public health. Clinicians should carefully consider their decision to prescribe PPIs for patients already having an elevated risk of fracture because of age or other factors.

Serotonin toxicity: a short review of the literature and two case reports involving citalopram.

The serotonin toxicity (ST) is a potentially life-threatening adverse drug reaction results from therapeutic drug use, intentional self-poisoning, or inadvertent interactions between drugs. ST can be caused by a single or a combination of drugs with serotonergic activity due to excessive serotonergic agonism on central nervous system and peripheral serotonergic receptors (monoamine oxidase inhibitors, tricyclic antidepressants, SSRIs, opiate analgesics, over-the-counter cough medicines, antibiotics, weight-reduction agents, antiemetics, antimigraine agents, drugs of abuse, H2-antagonist and herbal products). The serotonin toxicity is often described as a clinical triad of mental-status changes (agitation and excitement with confusion), autonomic hyperactivity (diaphoresis, fever, tachycardia, and tachypnea), neuromuscular abnormalities (tremor, clonus, myoclonus, and hyperreflexia) and, in the advanced stage, spasticity; not all of these findings are consistently present. In this article, we describe two cases of ST due to interaction between Citalopram and two CYP2D6 inhibitors: Cimetidine and Topiramate and their clinical resolution after treatment discontinuation.

No dose adjustment on coadministration of the PDE4 inhibitor roflumilast with a weak CYP3A, CYP1A2, and CYP2C19 inhibitor: an investigation using cimetidine.

This nonrandomized, fixed-sequence, 2-period crossover study investigated potential pharmacokinetic interactions between the phosphodiesterase 4 inhibitor roflumilast, currently in clinical development for the treatment of chronic obstructive pulmonary disease, and the histamine 2 agonist cimetidine. Participants received roflumilast, 500 µg once daily, on days 1 and 13. Cimetidine, 400 mg twice daily, was administered from days 6 to 16. Pharmacokinetic analysis of roflumilast and its active metabolite roflumilast N-oxide was performed, and the ratio of geometric means for roflumilast alone and concomitantly with steady-state cimetidine was calculated. The effect of cimetidine on the total PDE4 inhibitory activity (tPDE4i; total exposure to roflumilast and roflumilast N-oxide) was also calculated. Coadministration of steady-state cimetidine increased mean tPDE4i of roflumilast and roflumilast N-oxide by about 47%. The maximum plasma concentration (C(max)) of roflumilast increased by about 46%, with no effect on C(max) of roflumilast N-oxide. The increase in tPDE4i of roflumilast and roflumilast N-oxide following coadministration with cimetidine was mainly due to the inhibitory effect of cimetidine on cytochrome P450 (CYP) isoenzymes CYP1A2, CYP3A, and CYP2C19. These moderate changes indicate that dose adjustment of roflumilast is not required when coadministered with a weak inhibitor of CYP1A2, CYP3A, and CYP2C19, such as cimetidine.