Simvastatin-fluconazole causing rhabdomyolysis

Interaction and potential mechanisms between atorvastatin and voriconazole, agents used to treat dyslipidemia and fungal infections

Purpose: Voriconazole (VOR) is combined with atorvastatin (ATO) to treat fungal infections in patients with dyslipidemia in clinical practice. However, the pharmacokinetic interactions and potential mechanisms between them are unknown. Therefore, this study aimed to investigate the pharmacokinetic interactions and potential mechanisms between ATO and VOR. Patients and methods: We collected plasma samples from three patients using ATO and VOR. Rats were administered either VOR or normal saline for 6 days, followed by a single dose of 2 mg/kg ATO, and then plasma samples were collected at different time points. The incubation models of human liver microsomes or HepG2 cells were constructed in vitro. A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) system was developed to determine the concentration of ATO, 2-hydroxy-ATO, 4-hydroxy-ATO, and VOR. Results: In patients, VOR significantly reduced the metabolism of ATO and slowed the formation of 2-hydroxy- and 4-hydroxy-ATO. In rats pretreated with orally administered VOR for 6 days or normal saline given a single dose of 2 mg/kg ATO administered orally on Day 6, the t1/2 of ATO was significantly prolonged from 3.61 to 6.43 h, and the area under the concentration-time curve (AUC0-24h) values of ATO increased from 53.86 to 176.84 h μg.L-1. However, the pharmacokinetic parameters of VOR (20 mg/kg) with or without pretreatment with ATO (2 mg/kg) only slightly changed. In vitro studies indicated that VOR inhibited the metabolism of ATO and testosterone, and the IC50 values were 45.94 and 49.81 μM. However, no significant change in transporter behaviors of ATO was observed when VOR or transporter inhibitors were co-administered. Conclusion: Our study demonstrated that VOR has significant interactions with ATO, probably due to VOR's inhibition of the CYP3A4-mediated metabolism of ATO. Based on the clinical cases and potential interactions, the basic data obtained in our study are expected to help adjust the dose of ATO and promote the design of rational dosage regimens for pharmacotherapy for fungal infections in patients with dyslipidemia.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

Differences in discontinuation of statin treatment in women and men with advanced cancer disease

Background

Statins are often discontinued in patients with advanced cancer since the net effect of treatment is considered negative. However, guidelines concerning discontinuation of statin treatment are lacking. The aim of this study was to investigate any differences in time of discontinuation of statin treatment between men and women with advanced cancer disease.

Methods

Medical records from 195 deceased palliative cancer patients from a previous study cohort were reviewed. Patients treated with statins 2 years before death were identified as “statin users.” The time of discontinuation of statin therapy was identified and correlated to time of death. Only patients that had incurable cancer disease at time of statin discontinuation were included in the analysis.

Results

Fifty-four patients were identified as statin users, 29 women and 25 men. The average time span between discontinuation of statin treatment and time of death was significantly longer in women than in men, 10 months compared to 4 months (p < 0.01), with a range of 1–24 months among women and 1–12 months for men. All patients died due to their cancer disease. More men than women had a history of stroke or cardiac infarction (p = 0.02). There were no differences in age, socioeconomic factors, or survival time from study inclusion between men and women. There was no difference in self-assessed quality of life (QoL) between statin users who had discontinued statin treatment and those who are still on treatment. Men generally assessed their QoL lower than women in this study (p = 0.03).

Conclusion

Statin treatment was discontinued earlier in women than in men in patients with advanced cancer. The data suggest that statins may be discontinued earlier in men as well, since earlier discontinuation did not affect cardiovascular mortality.

Statin-associated rhabdomyolysis triggered by drug-drug interaction with itraconazole

A 47-year-old woman had been treated with high-dose simvastatin for several years. After systemic treatment with the antifungal agent itraconazole, she developed muscle pain and highly elevated levels of creatine kinase and myoglobin. Muscle biopsy was compatible with statin-associated rhabdomyolysis, probably caused by a drug-drug interaction between simvastatin and itraconazole. The patient made full recovery. Three commonly used statins-simvastatin, atorvastatin and lovastatin-are metabolised by the liver enzyme CYP3A4. Several potent inhibitors of this enzyme are known, for example, azole antifungal agents such as itraconazole and posaconazole. If antifungal treatment is indicated in a patient using a CYP3A4-metabolised statin, we recommend (1) topical administration of the antifungal agent if possible, (2) the use of a non-CYP3A4-inhibiting antifungal drug such as terbinafine or (3) temporary discontinuation of statin treatment.

Rhabdomyolysis due to Trimethoprim-Sulfamethoxazole Administration following a Hematopoietic Stem Cell Transplant

Rhabdomyolysis, a syndrome of muscle necrosis, is a life-threatening event. Here we describe the case of a patient with chronic myeloid leukemia who underwent a haploidentical stem cell transplant and subsequently developed rhabdomyolysis after beginning trimethoprim-sulfamethoxazole (TMP/SMX) prophylaxis therapy. Rechallenge with TMP/SMX resulted in a repeat episode of rhabdomyolysis and confirmed the association. Withdrawal of TMP/SMX led to sustained normalization of creatine kinase levels in the patient. A high index of suspicion is necessary to identify TMP/SMX as the cause of rhabdomyolysis in immunocompromised patients.

Drug interactions in general dental practice--considerations for the dental practitioner

The aim of this article is to explore the diverse and complex nature of pharmacological drug-drug interactions in the general dental practice setting. Using published NHS statistics, this article will highlight medications for common medical conditions that could interact with frequently prescribed drugs by the general dental practitioner.

Drug interactions with statins

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are generally well tolerated as monotherapy. Statins are associated with two important adverse effects, asymptomatic elevation in liver enzymes and myopathy. Myopathy is most likely to occur when statins are administered with other drugs. Statins are substrates of multiple drug transporters (including OAT- -P1B1, BCRP and MDR1) and several cytochrome P450 (CYP) enzymes (including CYP3A4, CYP2C8, CYP2C19, and CYP2C9). Possible adverse effects of statins can occur due to interactions in concomitant use of drugs that substantially inhibit or induce their methabolic pathway. This review summarizes the most important interactions of statins.

Rhabdomyolysis after Concomitant Use of Simvastatin and Voriconazole in an Allogeneic Stem Cell Transplant Patient

Objective:

To report a case of rhabdomyolysis after concomitant use of simvastatin and voriconazole.

Case Summary:

A 65-year-old white male, weight 66 kg, 79 months post allogeneic stem cell transplant for chronic lymphocytic leukemia, was on a stable medication regimen that included voriconazole. He was hospitalized with weakness and elevated creatine kinase a few weeks after initiation of simvastatin for treatment of hyperlipidemia. His symptoms resolved and creatine kinase level returned to within the normal range after fluid administration and discontinuation of simvastatin.

Discussion:

The use of statins has become a standard in the treatment and prevention of atherosclerotic disease. Most statins are metabolized via the cytochrome P450 enzyme system. For simvastatin, metabolism occurs specifically via the CYP3A4 isoenzyme. Drugs known to inhibit this isoenzyme, such as voriconazole, can increase the risk for toxicities, including rhabdomyolysis, when used concomitantly with simvastatin. This case represents a probable drug-drug interaction, based on the Horn Drug Interaction Probability Scale.

Conclusions:

Due to the broad use of statins for the treatment and prevention of atherosclerotic disease, as well as the need for azole antifungals in the stem cell transplant population, interactions between these agents are becoming an increasing possibility. Care should be taken to minimize these interactions and, when feasible, a change to an alternative agent may be warranted to avoid adverse effects.

Computing with evidence Part II: An evidential approach to predicting metabolic drug-drug interactions

We describe a novel experiment that we conducted with the Drug Interaction Knowledge-base (DIKB) to determine which combinations of evidence enable a rule-based theory of metabolic drug-drug interactions to make the most optimal set of predictions. The focus of the experiment was a group of 16 drugs including six members of the HMG-CoA-reductase inhibitor family (statins). The experiment helped identify evidence-use strategies that enabled the DIKB to predict significantly more interactions present in a validation set than the most rigorous strategy developed by drug experts with no loss of accuracy. The best-performing strategies included evidence types that would normally be of lesser predictive value but that are often more accessible than more rigorous types. Our experimental methods represent a new approach to leveraging the available scientific evidence within a domain where important evidence is often missing or of questionable value for supporting important assertions.

Risk management of simvastatin or atorvastatin interactions with CYP3A4 inhibitors

BACKGROUND

Co-administration of cytochrome P450 (CYP) 3A4 inhibitors with simvastatin or atorvastatin is associated with increased risk of developing myopathy or rhabdomyolysis.

OBJECTIVE

To detect co-prescriptions of CYP3A4 inhibitors with simvastatin or atorvastatin in community pharmacies and assess the risk-preventive actions taken by the prescribing physicians who were alerted about the co-prescription by the pharmacist.

METHODS

This naturalistic study was performed during four separate 6-week periods in 2004 and 2005, and involved 110 Norwegian community pharmacists (25-30 in each period). Co-prescription of the selected CYP3A4 inhibitors diltiazem, verapamil, clarithromycin, erythromycin, fluconazole, itraconazole and ketoconazole with either simvastatin or atorvastatin was detected with the aid of a simple computer programme. In instances where the pharmacist alerted the prescribing physician about the co-prescription, information on possible strategies to minimize the risk associated with the interaction was also provided. Odds ratios (ORs) were estimated to describe the associations between prescription variables and frequencies of physician information and prescription change, respectively.

RESULTS

In total, 245 co-prescriptions of CYP3A4 inhibitors with simvastatin (134 events) or atorvastatin (111) were detected. Diltiazem (86 events), verapamil (72), erythromycin (48) and clarithromycin (29) were the most commonly co-prescribed CYP3A4 inhibitors. Physicians were informed in 168 out of 245 cases (68.6%). The prescription was subsequently changed in 100 out of 168 cases (59.5%). Another 50 physicians (29.8%) responded that they would consult the patient and monitor potential adverse effects, while only 18 physicians (10.7%) replied that they had already managed the interactions or considered the issue as irrelevant. The adjusted OR for the informing of the physician was 1.89 (95% CI 0.98, 3.63) in patients receiving a daily HMG-CoA reductase inhibitor ('statin') dose of >or=40 mg compared with patients receiving a statin dose of <40 mg/day. The adjusted OR for prescription change was 4.98 (95% CI 2.36, 10.52) if co-prescription was detected prior to the initiation of concurrent use compared with if it was detected during concurrent use.

CONCLUSION

Nine out of ten physicians changed prescriptions or monitored potential adverse effects when informed by community pharmacists about the risk associated with co-prescription of CYP3A4 inhibitors with simvastatin or atorvastatin. This suggests that an important risk factor for myotoxicity due to these statins could be minimized through interdisciplinary co-operation.

Polypill: For Pollyanna*

A single pill containing a statin, thiazide diuretic, β-blocker, angiotensin receptor antagonist, folate and ASA has been proposed for all people over age 55, with the aim of reducing cardiovascular disease by 80%. Unfortunately, there are insurmountable problems with choosing appropriate constituents of any such single remedy. Adverse effects, drug interactions, inter-individual variation in drug metabolism, and underlying causes of hypertension that differ between patients require individualized therapy. A single pill that will succeed in all patients is not only practically, but conceptually, an inappropriate approach for the prevention of cardiovascular disease.

Which statin should be used together with colchicine? Clinical experience in three patients with nephrotic syndrome due to AA type amyloidosis

Colchicine and statins are well known drugs that cause myopathy and neuropathy. Co-administration of certain drugs with statins may increase myotoxic effect, causing myopathy and varying degrees of rhabdomyolysis. Therefore, it is very crucial to know which statin should be used during a combination therapy including colchicine and other drugs. We present three cases with AA amyloidosis secondary to familial Mediterranean fever, who developed neuromyopathy while receiving the combination of colchicine and statin. We also briefly discussed the different metabolic pathways of statins and colchicine when used together.

Intensive management of risk factors for accelerated atherosclerosis: the role of multiple interventions

Patients at high risk of vascular events can reduce their risk by 75% to 80% through a combination of lifestyle changes and medical therapy. These include smoking cessation, a Mediterranean diet, daily exercise, maintaining a fit weight, moderate consumption of alcohol, effective control of blood pressure and diabetes, intensive treatment with lipid-lowering drugs and antiplatelet agents, and perhaps treatment with vitamins to lower homocysteine. Much of this is achieved primarily by the patient; physicians need to become better at assisting their patients in making lifestyle changes. Effective control of treatment-resistant hypertension can be improved by individualizing medical therapy to the underlying cause, based on measurement of plasma renin and aldosterone. Measurement of carotid plaque may be useful by providing feedback on the success of therapy.

Co-prescriptions with itraconazole and fluconazole as a signal for possible risk of drug–drug interactions: a four-year analysis from Italian general practice

PURPOSE

To determine the prevalence of concomitant use of drugs potentially responsible for interactions among itraconazole and fluconazole users in general practice.

METHODS

During the years 1999-2002, we obtained information from the 'Health Search Database', (HSD) an Italian general practice research database. Among a total sample of 457 672 eligible patients, we included those aged >16 years, and whose diagnoses could be classified as mycosis. Itraconazole and fluconazole users were then selected. A potentially drug-drug interaction (DDI) occurred when the use of concomitant drugs were recorded within +/-30 days from the date of the first azoles prescription. Interacting drugs were classified according to the summary of product characteristics (SPC) as provided by the Italian Pharmaceutical Repertory (REFI).

RESULTS

From 18 323 cases of mycosis, we selected 4843 itraconazole and 1446 fluconazole users. Potentially interacting drugs were prescribed in 8.7% of itraconazole and 6.1% of fluconazole users. For itraconazole, calcium channel blockers were the most common interacting drugs (3.3%), followed by statins (1.7%) and clarithromycin (1.3%), whereas gestoden + ethynylestradiol (2.5%) and benzodiazepines (1.8%) resulted as the most common interacting drugs among fluconazole users.

CONCLUSION

Data indicate a relevant prevalence of concomitant use of medications potentially leading to drug interactions among azoles users. Because of the wide use of these medications in general practice, they should be used with clinical monitoring in view of their known side effects as well as their potential risk for drug interaction.

Frequency of potential azole drug-drug interactions and consequences of potential fluconazole drug interactions

PURPOSE

To assess the frequency of potential azole-drug interactions and consequences of interactions between fluconazole and other drugs in routine inpatient care.

METHODS

We performed a retrospective cohort study of hospitalized patients treated for systemic fungal infections with an oral or intravenous azole medication between July 1997 and June 2001 in a tertiary care hospital. We recorded the concomitant use of medications known to interact with azole antifungals and measured the frequency of potential azole drug interactions, which we considered to be present when both drugs were given together. We then performed a chart review on a random sample of admissions in which patients were exposed to a potential moderate or major drug interaction with fluconazole. The list of azole-interacting medications and the severity of interaction were derived from the DRUGDEX System and Drug Interaction Facts.

RESULTS

Among the 4,185 admissions in which azole agents (fluconazole, itraconazole or ketoconazole) were given, 2,941 (70.3%) admissions experienced potential azole-drug interactions, which included 2,716 (92.3%) admissions experiencing potential fluconazole interactions. The most frequent interactions with potential moderate to major severity were co-administration of fluconazole with prednisone (25.3%), midazolam (17.5%), warfarin (14.7%), methylprednisolone (14.1%), cyclosporine (10.7%) and nifedipine (10.1%). Charts were reviewed for 199 admissions in which patients were exposed to potential fluconazole drug interactions. While four adverse drug events (ADEs) caused by fluconazole were found, none was felt to be caused by a drug-drug interaction (DDI), although in one instance fluconazole may have contributed.

CONCLUSIONS

Potential fluconazole drug interactions were very frequent among hospitalized patients on systemic azole antifungal therapy, but they had few apparent clinical consequences.

Rhabdomyolysis after simvastatin therapy in an HIV-infected patient with chronic renal failure

We encountered a 49-year-old HIV-infected man with chronic renal insufficiency who developed rhabdomyolysis after treatment with simvastatin. He recovered after initiating hemodialysis and discontinuing oral medications. Rhabdomyolysis most likely resulted from an excessive blood concentration of simvastatin caused by concomitant use of fluconazole in the presence of renal insufficiency.

Comparative pharmacokinetic interaction profiles of pravastatin, simvastatin, and atorvastatin when coadministered with cytochrome P450 inhibitors

Three-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitors (statins) are first-line treatments for hypercholesterolemia. Although exceedingly well tolerated, treatment with statins incurs a small risk of myopathy or potentially fatal rhabdomyolysis, particularly when coadministered with medications that increase their systemic exposure. Studies compared the multiple-dose pharmacokinetic interaction profiles of pravastatin, simvastatin, and atorvastatin when coadministered with 4 inhibitors of cytochrome P450-3A4 isoenzymes in healthy subjects. Compared with pravastatin alone, coadministration of verapamil, mibefradil, or itraconazole with pravastatin was associated with no significant changes in pravastatin pharmacokinetics. However, concomitant verapamil increased the simvastatin area under the concentration:time curve (AUC) approximately fourfold, the maximum serum concentration (C(max)) fivefold, and the active metabolite simvastatin acid AUC and C(max) approximately four- and threefold, respectively (all comparisons p <0.001). Similar (greater than fourfold) important increases in these parameters and a >60% increase in the serum half-life (p = 0.03) of atorvastatin were observed when coadministered with mibefradil. The half-life of atorvastatin also increased by approximately 60% (p = 0.052) when coadministered with itraconazole, which elicited a 2.4-fold increase in the C(max) of atorvastatin and a 47% increase in the AUC (p <0.001 for C(max) and AUC). Clarithromycin significantly (p <0.001) increased the AUC (and C(max)) of all 3 statins, most markedly simvastatin ( approximately 10-fold increase in AUC) and simvastatin acid (12-fold), followed by atorvastatin (greater than fourfold) and then pravastatin (almost twofold). Pravastatin has a neutral drug interaction profile relative to cytochrome P450-3A4 inhibitors, but these substrates markedly increase systemic exposure to simvastatin and atorvastatin.

Using a computerized drug prescription screening system to trace drug interactions in an outpatient setting

BACKGROUND

Drug-drug interactions are one of the main causes of adverse effects. These events have been studied most often in hospital settings; however, investigations on prescribing based on community practice have shown a high prevalence rate of potential drug interactions.

OBJECTIVE

To develop a computerized system able to trace drug interactions quickly through the identification of clinicians issuing potentially unsafe prescriptions.

METHODS

We retrospectively evaluated hazardous concomitant prescriptions of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) and azole antifungals, which were invoiced through 9 months of 2001 within an outpatient setting. The study was conducted in Badajoz, a southern Spanish province, and was divided in three 3-month periods according to the release of 2 warning notes on this drug combination by the Spanish Drug Agency. Prescriptions written during this period were optically scanned each month, and the resulting information, including data from patients, physicians, and drugs involved, was converted to a database and searched for potentially unsafe coprescriptions.

RESULTS

A total of 8342711 prescriptions were invoiced in the period of study, 174 of which were for a statin-azole combination. The number of these prescriptions remained fairly constant during periods I and II (63 and 71, respectively), decreasing to 40 in period III. Some clinicians (12.6%) repeatedly prescribed a hazardous drug combination at some point in this study, whereas 18 of 171 patients who received the hazardous coprescription at any time did so repeatedly within a given period. The impact of drug alerts was remarkably deeper in urban rather than rural care centers.

CONCLUSIONS

The computerized drug prescription handling system described here is able to readily identify physicians and patients who issue/consume hazardous drug combinations, thus allowing both the possibility of individually informing the healthcare professionals involved and early detection of adverse effects.

Drug interactions in dentistry

BACKGROUND

The hepatic and intestinal cytochrome, or CY, P450 enzyme system is responsible for the biotransformation of a multitude of drugs. Certain medications used in dentistry can act as substrates, inducers or inhibitors of this system.

METHODS

The authors conducted a MEDLINE search of articles appearing between 1976 and the present using the keywords "drug interactions" and "cytochrome P450," and reviewed reports involving dental therapeutic agents using PubMed links from an Indiana University CYP450 drug interaction table on the World Wide Web.

RESULTS

The antibiotics erythromycin and clarithromycin are potent inhibitors of CYP3A4 and can increase blood levels and toxicity of CYP3A4 substrates. Likewise, quinolone antibiotics such as ciprofloxacin inhibit the metabolism of CYP1A2 substrates. Other dental therapeutic agents are substrates for CYP2C9 (celecoxib, ibuprofen and naproxen), CYP2D6 (codeine and tramadol), CYP3A4 (methylprednisolone) and CYP2E1 (acetaminophen). Because codeine and tramadol are prodrugs, inhibition of their metabolism can lead to a diminution of their analgesic effects. While inducers of acetaminophen metabolism, including alcohol, theoretically can increase the proportion of it that is biotransformed into a potentially hepatotoxic metabolite, recent research suggests that concomitant alcohol intake does not increase the hepatotoxic potential of therapeutic doses of acetaminophen.

CONCLUSIONS

A number of clinically significant drug interactions can arise with dental therapeutic agents that act as substrates or inhibitors of the CYP450 system. Clinical Implications. As polypharmacy continues to increase, the likelihood of adverse drug interactions in dentistry will increase as well. Ensuring that patients' medical histories are up to date and acquiring knowledge of the various substrates, inducers and inhibitors of the CYP450 system will help practitioners avoid potentially serious adverse drug interactions.