Diclofenac and the Risk of Rhabdomyolysis: Analysis of Publications and the WHO Global Pharmacovigilance Database.

BACKGROUND: Diclofenac, a nonsteroidal anti-inflammatory drug, is not a documented cause of rhabdomyolysis in the Summaries of Product Characteristics held by major regulators. There are, however, eight published single case reports that associate rhabdomyolysis with diclofenac. OBJECTIVE: Triggered by a serious local case report, this study was conducted to evaluate the evidence for a causal association between diclofenac and rhabdomyolysis. PATIENTS AND METHODS: A descriptive analysis of rhabdomyolysis associated with diclofenac was conducted by mining data from the WHO Global Database of Individual Case Safety Reports, VigiBase, and published case reports. RESULTS: 70 eligible cases were retrieved from VigiBase. The median age was 56.5 years (range 1-90). Where reported precisely (26 reports), the median time to onset of rhabdomyolysis following administration of diclofenac was 3 days. In 20 cases, diclofenac was reported as a sole suspect and was solely administered in 14 of these. In 30 cases, rhabdomyolysis abated following withdrawal of diclofenac. Seven of these cases fulfilled the WHO-UMC case-causality assessment criteria for 'probable'. Diclofenac was probably an indirect cause in another five reports where rhabdomyolysis ensued from injection-site necrosis. There were eight fatalities and intramuscular administration was over-represented in this group. In 27 patients taking lipid-lowering agents, the incidence of acute kidney injury with rhabdomyolysis was 62.9% compared with 37.1% for the whole cohort. Off-label use of diclofenac for minor or undiagnosed conditions was reported. CONCLUSION: Currently available data suggests a causal link between diclofenac and rhabdomyolysis either directly or indirectly.

The Association between Metformin Therapy and Lactic Acidosis.

INTRODUCTION AND OBJECTIVES: There is increasing evidence to suggest that therapeutic doses of metformin are unlikely to cause lactic acidosis. The aims of this research were (1) to formally evaluate the association between metformin therapy and lactic acidosis in published case reports using two causality scoring systems, (2) to determine the frequency of pre-existing independent risk factors in published metformin-associated lactic acidosis cases, (3) to investigate the association between risk factors and mortality in metformin-associated lactic acidosis cases, and (4) to explore the relationship between prescribed metformin doses, elevated metformin plasma concentrations and the development of lactic acidosis in cases with chronic renal impairment. METHODS: A systematic review was conducted to identify metformin-associated lactic acidosis cases. Causality was assessed using the World Health Organisation-Uppsala Monitoring Centre system and the Naranjo adverse drug reaction probability scale. Compliance to dosing guidelines was investigated for cases with chronic renal impairment as well as the association between steady-state plasma metformin concentrations prior to admission. RESULTS: We identified 559 metformin-associated lactic acidosis cases. Almost all cases reviewed (97%) presented with independent risk factors for lactic acidosis. The prescribed metformin dose exceeded published guidelines in 60% of cases in patients with impaired kidney function. Metformin steady-state plasma concentrations prior to admission were predicted to be below the proposed upper limit of the therapeutic range of 5 mg/L. CONCLUSIONS: Almost all cases of metformin-associated lactic acidosis reviewed presented with independent risk factors for lactic acidosis, supporting the suggestion that metformin plays a contributory role. The prescribed metformin dose, on average, exceeded the dosing recommendations by 1000 mg/day in patients with varying degrees of renal impairment but the predicted pre-admission plasma concentrations did not exceed the therapeutic range.

Suspected Hepatotoxicity With a Supercritical Carbon Dioxide Extract of Artemisia annua in Grapeseed Oil Used in New Zealand.

A case series of hepatotoxicity associated with an extract of Artemisia annua L. was identified through the New Zealand spontaneous adverse drug reaction reporting system. A. annua extract, produced using a supercritical carbon dioxide extraction method and formulated with grapeseed oil, has been marketed in New Zealand as a natural product for joint health. As of 31 January 2019, the New Zealand Pharmacovigilance Centre had received 29 reports of hepatic adverse reactions occurring in patients taking A. annua extract in grapeseed oil. The case reports were assessed for patient and adverse reaction characteristics, patterns of A. annua extract use and causality (based on the WHO-UMC system for standardized case causality assessment). Patients were aged 47 to 93 years (median 67). Time to onset of hepatotoxicity from starting A. annua extract was 7 days to approximately 12 months in the 23 reports with this information. Nineteen of these reports indicated onset within 12 weeks. A. annua extract was the sole suspect medicine in 27 reports. A few patients had possible predisposing conditions. Twenty-seven patients were reported to have recovered or improved on stopping A. annua extract. Nine patients required hospital admission. The pattern of hepatic injury varied. Jaundice, often with pruritus and dark urine, was experienced by 16 patients. There was considerable consistency across case reports from various reporters. We assessed the case reports as a series using the Bradford Hill guidelines for causal inference and concluded that there was a safety signal of a causal association between the A. annua extract and hepatotoxicity sufficient to be communicated and investigated further.

Case Series Analysis of New Zealand Reports of Rapid Intense Potentiation of Warfarin by Roxithromycin.

INTRODUCTION: We undertook an analysis of all the reports to the New Zealand Centre for Adverse Reactions Monitoring of a roxithromycin/warfarin interaction after two recent reports described intense rapid warfarin potentiation. The interaction was first published in 1995. Cytochrome P450 3A4 inhibition has been the proposed mechanism but has limited biologic plausibility. There are suggestions that the clinical significance of the interaction may be increased by severe illness, polypharmacy, renal dysfunction, older age and increased warfarin sensitivity. METHODS: To investigate the potentiating effect of warfarin on roxithromycin in this New Zealand case series, the reports were reviewed to identify patients at risk, compare the reporting pattern with published Australian data and evaluate the appropriateness of current prescribing advice. RESULTS: Thirty patient reports were identified. The age range was 23-88 years, mean 66.8, median 73.0 (standard deviation 17.7) and the international normalised ratios after roxithromycin commencement ranged from 3.6 to 16.7 (mean 7.6, median 7.6, standard deviation 3.6). For eight patients with measurements on day 3, international normalised ratios were 4.3-16.7 (mean 10.4, median 8.8, standard deviation 4.4). Four patients had serious haemorrhage. Indications for roxithromycin were a range of respiratory tract infections. Anticoagulation was stable for most patients prior to acute infection. Serious infection occurred in 54.5% (12 of 22 patients with information). Polypharmacy (five or more medicines daily) was used by 36.7% of patients long term, increasing acutely to 83.3%, including additional potentially interacting medicines. Warfarin daily dose (1.5-13.0 mg, mean 4.4, median 4.0, standard deviation 2.2) was moderate to low. Pre-roxithromycin international normalised ratio values ranged from 1.4 to 3.7, mean and median 2.5, standard deviation 0.5. A high proportion of interactions were observed between warfarin and roxithromycin compared with other macrolides and compared with cytochrome P450 3A4-related macrolide interactions. The pattern was similar to published Australian data. CONCLUSION: In this case series, the high prevalence of acute polypharmacy, including potentially interacting medicines, and serious infection suggests that they may have contributed to warfarin potentiation and increased the clinical significance of a roxithromycin/warfarin interaction.

Impact of New Genomic Technologies on Understanding Adverse Drug Reactions.

It is well established that variations in genes can alter the pharmacokinetic and pharmacodynamic profile of a drug and immunological responses to it. Early advances in pharmacogenetics were made with traditional genetic techniques such as functional cloning of genes using knowledge gained from purified proteins, and candidate gene analysis. Over the past decade, techniques for analysing the human genome have accelerated greatly as knowledge and technological capabilities have grown. These techniques were initially focussed on understanding genetic factors of disease, but increasingly they are helping to clarify the genetic basis of variable drug responses and adverse drug reactions (ADRs). We examine genetic methods that have been applied to the understanding of ADRs, review the current state of knowledge of genetic factors that influence ADR development, and discuss how the application of genome-wide association studies and next-generation sequencing approaches is supporting and extending existing knowledge of pharmacogenetic processes leading to ADRs. Such approaches have identified single genes that are major contributing genetic risk factors for an ADR, (such as flucloxacillin and drug-induced liver disease), making pre-treatment testing a possibility. They have contributed to the identification of multiple genetic determinants of a single ADR, some involving both pharmacologic and immunological processes (such as phenytoin and severe cutaneous adverse reactions). They have indicated that rare genetic variants, often not previously reported, are likely to have more influence on the phenotype than common variants that have been traditionally tested for. The problem of genotype/phenotype discordance affecting the interpretation of pharmacogenetic screening and the future of genome-based testing applied to ADRs are also discussed.

Renal replacement therapy associated with lithium nephrotoxicity in New Zealand.

AIM: To document the numbers and characteristics of New Zealand patients commencing renal replacement therapy because of end-stage kidney disease attributed to lithium treatment, and to calculate incidence rates. METHOD: Data on such patients were provided by the Australia and New Zealand Dialysis and Transplant Registry from the start of the Registry in 1977 until 2013. Numbers of patients prescribed lithium in the community were provided by the Ministry of Health for 2009-2013; earlier years had fewer than 96% of prescriptions for lithium linked to individuals by their unique National Health Index number. Time trends were analysed by linear, logistic and Poisson regression. Incidence rates were also calculated for five-year periods. RESULTS: Thirty-five new patients were located with 'lithium toxicity' as their primary renal disease, starting the year after 'lithium toxicity' was included in the standard list (1995). A broader search for lithium within 'other' causes and 'other' comorbidities did not yield further patients. The mean age at the start of renal replacement therapy was 61.1 years (SD 9.2). Twenty-five patients were female. For 1996 onwards, new patient numbers increased on average by 8% per year (95% CI 1 to 15%) and incidence rates increased by 7% per year (95% CI 0 to 14%), an approximate doubling per decade. Form 2007-2011, the average annual incidence per million population was 0.74 (95% CI 0.43 to 1.21) for New Zealand, similar to that reported elsewhere: 0.78 (95% CI 0.67 to 0.90) for Australia and 0.91 (95% CI 0.50 to 1.52) for southern Sweden. Prescription rates across the three countries were also similar. In New Zealand between 2009 and 2013, over 7,500 patients were prescribed lithium each year. CONCLUSION: Dosing and monitoring of patients prescribed lithium should follow guidelines, not only to avoid future psychiatric episodes and acute toxicity but also because such adherence may reduce uncommon but serious outcomes of long-term treatment such as end-stage kidney disease.

Varenicline and abnormal sleep related events.

STUDY OBJECTIVES: To assess adverse drug reaction reports of "abnormal sleep related events" associated with varenicline, a partial agonist to the α4ß2 subtype of nicotinic acetylcholine receptors on neurones, indicated for smoking cessation. DESIGN: Twenty-seven reports of "abnormal sleep related events" often associated with abnormal dreams, nightmares, or somnambulism, which are known to be associated with varenicline use, were identified in the World Health Organisation (WHO) Global Individual Case Safety Reports Database. Original anonymous reports were obtained from the four national pharmacovigilance centers that submitted these reports and assessed for reaction description and causality. MEASUREMENTS AND RESULTS: These 27 reports include 10 of aggressive activity occurring during sleep and seven of other sleep related harmful or potentially harmful activities, such as apparently deliberate self-harm, moving a child or a car, or lighting a stove or a cigarette. Assessment of these 17 reports of aggression or other actual or potential harm showed that nine patients recovered or were recovering on varenicline withdrawal and there were no consistent alternative explanations. Thirteen patients experienced single events, and two had multiple events. Frequency was not stated for the remaining two patients. CONCLUSIONS: The descriptions of the reports of aggression during sleep with violent dreaming are similar to those of rapid eye movement sleep behavior disorder and also nonrapid eye movement (NREM) sleep parasomnias in some adults. Patients who experience somnambulism or dreams of a violent nature while taking varenicline should be advised to consult their health providers. Consideration should be given to clarifying the term sleep disorders in varenicline product information and including sleep related harmful and potentially harmful events.

Severe muscle symptoms with lipid-lowering agents may be confused with neurogenic claudication associated with spinal canal stenosis.

BACKGROUND: Screening of the WHO global individual case safety report database (VigiBase) has recently identified case reports with HMG CoA reductase inhibitors and muscle symptoms co-reported with spinal stenosis. In some reports spinal stenosis appears to have been listed as a coincidental finding. OBJECTIVE: To assess reports with sufficient information to ascertain if they suggested that there may have been diagnostic confusion between muscle symptoms attributable to HMG CoA reductase inhibitors with or without ezetimibe and symptoms of spinal stenosis. METHOD: Reports were examined for patient demographics, past history, clinical and investigational findings, co-prescribed medicines and outcomes. RESULTS: Three case histories recorded details suggestive of diagnostic confusion between severe and disabling muscle symptoms affecting the lower limbs attributable to an HMG CoA reductase inhibitor with and without ezetimbe and symptoms of neurogenic claudication due to spinal stenosis. The statins were not discontinued promptly leading to prolonged morbidity. Serum creatine kinase levels (CK) were normal in two patients and not recorded for the third. CONCLUSION: The reports include two safety issues, firstly the need to consider HMG CoA reductase inhibitors as a cause of severe lower limb muscle symptoms even in the presence of spinal stenosis and normal CK levels and the second, the need to measure serum creatine kinase when these symptoms occur to detect progression of myopathy and potentially serious outcomes.

Alendronate-induced synovitis.

We describe 7 cases of synovitis or arthritis occurring after commencement of alendronate for treatment of osteoporosis. These were cases from our practice or notified to the New Zealand Pharmacovigilance Centre, Dunedin, New Zealand. There was no evidence of rheumatoid arthritis, pyrophosphate arthropathy, or seronegative arthritis in any patient. Symptoms recurred on rechallenge in 5 of the cases. We conclude alendronate should be considered as a possible cause of synovitis or polyarthritis in patients treated with it in the absence of any other pathology.

Leflunomide-associated infections in rheumatoid arthritis.

OBJECTIVE: To determine the prevalence of severe infections in patients with rheumatoid arthritis (RA) prescribed leflunomide in North Canterbury, New Zealand. METHODS: A case-note audit of all Christchurch Hospital patients with RA prescribed leflunomide between 2002 and 2006 was performed. The criterion for severe infection was inpatient hospitalization. Relevant reports to the national Pharmacovigilance Centre were also examined. RESULTS: Since January 2002, 171 patients with RA have commenced taking leflunomide. Ninety-nine of 171 (57.9%) patients were also prescribed prednisone. Combination disease modifying antirheumatic drug therapy was common, with 82/171 (48.0%) taking methotrexate (MTX), 15/171 (8.8%) hydroxy-chloroquine, 11/171 (6.4%) sulfasalazine, and 8/171 (4.7%) anti-tumor necrosis factor therapy. Eleven patients developed infection requiring hospitalization while taking leflunomide including: lower respiratory tract infections (3), cellulitis (2), disseminated herpes zoster (2), probable TB liver (1), abdominal sepsis (1), mycotic aneurysm (1) and gastroenteritis (1). Nine of the 11 patients were also taking corticosteroids or corticosteroids with MTX. The 171 patients were treated for a total of 4005 months, giving an incidence for severe infection of 3.30/100 patient-years (95% CI 1.65-5.90). Patients at increased risk were those with severe disease and taking concomitant MTX and corticosteroids. The NZ Pharmacovigilance Centre has received 7 additional reports of severe infections in patients with RA taking leflunomide. Reported cases include probable pulmonary TB (1), pneumocystis pneumonia (1), other pulmonary infection (2), and septicemia (3) including a case of infective endocarditis. Four occurred in combination with MTX, one with adalimumab. All 5 patients were also taking -corticosteroids. CONCLUSION: We believe this observed rate of serious infection is acceptable in the context of optimally treating active RA. Patients with severe disease and taking combination MTX and corticosteroids are at greatest risk. In our experience, once established, infections may rapidly progress in patients with RA taking leflunomide, and early cholestyramine washout is strongly recommended.