Personalised medicine in hypercholesterolaemia: the role of pharmacogenetics in statin therapy

Statins are the first-line choice in Lipid-lowering therapy to reduce cardiovascular risk. In a continuous attempt to optimise treatment success, there is a need for additional research on genes and related molecular pathways that can determine the efficacy and toxicity of lipid-lowering drugs. Several variations within genes associated with lipid metabolism, including those involved in uptake, distribution and metabolism of statins have been reported. The purpose of this study was to evaluate the effect of genetic variations in the key genes responsible for statins' metabolism and their role in personalised medicine and pharmacogenetic testing (PGx) in patients treated with such drugs. Genetic assessment for specific known SNPs within the most known genes such as ABCG2, SLCO1B1, CYP3A4, and HMGCR, appears likely to predict the efficacy of statin therapy and prevent their side effects but does not necessarily reduce the risk of cardiovascular events. Key Messages Hypercholesterolaemia patients show different response to statin therapy. Several variations within genes associated with statin metabolism have been investigated. Genetic assessment for specific known SNPs within the most known genes may improve the efficacy of statins treatment and prevent their side effects.

Interaction potential between clarithromycin and individual statins-A systematic review

The high prevalence of statin and clarithromycin utilization creates potential for overlapping use. The objectives of this MiniReview were to investigate the evidence base for drug-drug interactions between clarithromycin and currently marketed statins and to present management strategies for these drug combinations. We conducted a systematic literature review following PRISMA guidelines with English language studies retrieved from PubMed and EMBASE (from inception through March 2019). We included 29 articles (16 case reports, 5 observational, 5 clinical pharmacokinetic and 3 in vitro studies). Based on mechanistic/clinical studies involving clarithromycin or the related macrolide erythromycin (both strong inhibitors of CYP3A4 and of hepatic statin uptake transporters OATP1B1 and OATP1B3), clarithromycin is expected to substantially increase systemic exposure to simvastatin and lovastatin (>5-fold increase in area under the plasma concentration-time curve (AUC)), moderately increase AUCs of atorvastatin and pitavastatin (2- to 4-fold AUC increase) and slightly increase pravastatin exposure (≈2-fold AUC increase) while having little effect on fluvastatin or rosuvastatin. The 16 cases of statin-clarithromycin adverse drug reactions (rhabdomyolysis (n = 14) or less severe clinical myopathy) involved a CYP3A4-metabolized statin (simvastatin, lovastatin or atorvastatin). In line, a cohort study found concurrent use of clarithromycin and CYP3A4-metabolized statins to be associated with a doubled risk of hospitalization with rhabdomyolysis or other statin-related adverse events as compared with azithromycin-statin co-administration. If clarithromycin is necessary, we recommend (a) avoiding co-administration with simvastatin, lovastatin or atorvastatin; (b) withholding or dose-reducing pitavastatin; (c) continuing pravastatin therapy with caution, limiting pravastatin dose to 40 mg daily; and (d) continuing fluvastatin or rosuvastatin with caution.

Trends and variations in outpatient coprescribing of simvastatin or atorvastatin with potentially interacting drugs in Thailand

Background:

The aim of this study was to assess trends and variations in coprescribing of simvastatin or atorvastatin with interacting drugs in Thailand.

Methods:

Outpatient prescriptions between 2013 and 2015 in 26 tertiary care hospitals were analyzed for statin coprescribing. The proportion of patients exposed to coprescribing was estimated for semi-annual changes, using a time-series analysis and for hospital variations, using an interquartile range (IQR).

Results:

The coprescribing of simvastatin with all contraindicated drugs in 10 university and 16 general hospitals, respectively, was 3.6 and 3.1% in 2013, then decreased to 3.2 and 2.6% in 2014 and to 2.6 and 2.0% in 2015. The drug most frequently coprescribed with simvastatin, on a decreasing trend (by 0.19 percentage points) was gemfibrozil (in 2013, 2014 and 2015, respectively; 2.9, 2.3 and 2.0% in university hospitals, and 2.5, 2.0 and 1.6% in general hospitals). A similar trend was found in atorvastatin-gemfibrozil coprescribing. Patients coprescribed simvastatin with the rest of the contraindicated drugs were relatively stable at 0.6–0.8%. No protease inhibitors were coprescribed with simvastatin and atorvastatin. The IQR of simvastatin coprescribing in the university hospitals was smaller than that in the general hospitals and decreased over time.

Conclusions:

Coprescriptions potentially leading to drug interactions with simvastatin in Thailand were observed although the contraindicated drugs were acknowledged. Mutual awareness among health professionals and the implementation of electronic prescribing should be strengthened as zero drug interaction was possible as in the case of protease inhibitors in the present study.

Prevalence of potential drug interactions in Thai patients receiving simvastatin: The causality assessment of musculoskeletal adverse events induced by statin interaction

Drug-drug interactions are one of the major risk factors associated with statin-induced myopathy. Although simvastatin is widely used in Thailand, studies investigating the prevalence of potential simvastatin-drug interactions (SDIs) and its clinical relevance in Thai population are still limited. We aimed to investigate the prevalence of potential SDIs (phase 1 study) and musculoskeletal adverse effects (AEs) associated with those interactions (phase 2 study). A phase 1 study was retrospectively conducted with outpatients at a 60-bed hospital who received simvastatin between July 1, 2012 and June 30, 2013. In phase 2, study was cross-sectionally conducted in outpatients whose prescriptions contain potential SDIs. Musculoskeletal AEs were evaluated by using symptom checklist questionnaires and measuring plasma creatinine kinase (CK). The causal relationship between the AEs and the potential SDIs was assessed using a Drug Interaction Probability Scale.

Out of 3447 simvastatin users, potential SDIs were found in 314 patients (9.1%). The prevalence of prescriptions containing potential SDIs was in the range of 4.7–6.0%. Two-thirds of the potential SDIs were rated to be highly significant while more than 70% were in contraindication list. The most common precipitant drugs were gemfibrozil (382 prescriptions), colchicine (171 prescriptions) and amlodipine (152 prescriptions). Of 49 patients recruited into phase 2 study, we found that 31 patients (63.3%) had myopathy. Myalgia was the most frequently identified AEs (n = 18, 58.1%), followed by asymptomatic rising CK (n = 8, 25.8%), and myositis (n = 5, 16.1%). Musculoskeletal AEs associated with SDIs were found in 16 patients (51.6%). Of these, we found 50.0%, 31.3% and 18.8% had asymptomatic rising CK, myalgia, and myositis, respectively. Precipitant drugs associated with myopathy were amlodipine (2 possible cases), colchicine (3 possible cases), gemfibrozil (8 possible and 1 probable cases), nevirapine (1 possible case), and nicotinic acid (1 possible case).

Potential SDIs have been found in the Thai population with a prevalence that is consistent with previous reports. Half of the musculoskeletal AEs identified were associated with SDIs. Systematic screening and management with interdisciplinary co-operation are needed to increase awareness of potential SDIs.

Omega-3 carboxylic acids monotherapy and combination with statins in the management of dyslipidemia

The 2013 American College of Cardiology/American Heart Association guidelines on cholesterol management placed greater emphasis on statin therapy given the well-established benefits in primary and secondary prevention of cardiovascular disease. Residual risk may remain after statin initiation, in part because of triglyceride-rich lipoprotein cholesterol. Several large trials have failed to show benefit with non-statin cholesterol-lowering medications in the reduction of cardiovascular events. Yet, subgroup analyses showed a benefit in those with hypertriglyceridemia and lower high-density lipoprotein cholesterol level, a high-risk pattern of dyslipidemia. This review discusses the benefits of omega-3 carboxylic acids, a recently approved formulation of omega-3 fatty acid with enhanced bioavailability, in the treatment of dyslipidemia both as monotherapy and combination therapy with a statin.

Statin drug-drug interactions in a Romanian community pharmacy

BACKGROUND AND AIM

Statins are frequently prescribed for patients with dyslipidemia and have a well-established safety profile. However, when associated with interacting dugs, the risk of adverse effects, especially muscular toxicity, is increased. The objective of this study was to identify, characterize and quantify the prevalence of the potential drug-drug interactions (pDDIs) of statins in reimbursed prescriptions from a community pharmacy in Bucharest.

METHODS

We analyzed the reimbursed prescriptions including statins collected during one month in a community pharmacy. The online program Medscape Drug Interaction Checker was used for checking the drug interactions and their classification based on severity: Serious - Use alternative, Significant - Monitor closely and Minor.

RESULTS

132 prescriptions pertaining to 125 patients were included in the analysis. Our study showed that 25% of the patients who were prescribed statins were exposed to pDDIs: 37 Serious and Significant interactions in 31 of the statins prescriptions. The statins involved were atorvastatin, simvastatin and rosuvastatin.

CONCLUSIONS

Statin pDDIs have a high prevalence and patients should be monitored closely in order to prevent the development of adverse effects that result from statin interactions.

Potential statin-drug interactions: prevalence and clinical significance

Background

Statins are cholesterol-lowering drugs widely used for cardiovascular prevention. Although safe when used alone, in combination with other drugs the likelihood of adverse drug reactions increases significantly. The exposure of the Bulgarian population to coprescriptions leading to potential statin-drug interactions is currently unknown.

Objective

The aim of this study was to investigate the incidence of coprescriptions involving statins and to compare the exposure of outpatients and inpatients to potential statin-drug interactions.

Setting

A cardiology clinic of the teaching University hospital in Varna, Bulgaria.

Method

This observational retrospective study examined the medical records of hospitalized patients prescribed a statin in combination with potentially interacting drugs. Patients who entered the hospital with a statin coprescription (considered outpatients) were compared with those coprescribed a statin at discharge from hospital (considered inpatients). Potentially interacting drugs included inhibitors and inducers of cytochrome P450 (CYP) enzymes and drugs of narrow safety margin (coumarin anticoagulants, digitalis).

Main outcome measure

The proportion of patients exposed to statin coprescriptions with potentially interacting drugs at hospital admission and discharge. Secondary outcome measures: laboratory evidence supporting possible statin-drug interactions.

Results

Out of 1641 hospitalized patients examined, 572 were prescribed a statin, either at hospital admission or discharge. Simvastatin was most commonly prescribed and simvastatin-drug coprescription predominated, especially at discharge. The exposure to all potential statin-drug interactions was similar at hospital admission (26.1%) and discharge (24.4%), as was the exposure to statin combinations with CYP inhibitors, 6.4% and 4%, correspondingly. Overall, more coprescriptions were generated, than were eliminated by hospital physicians. Amiodarone was the CYP inhibitor most frequently coprescribed. Of all interacting drugs acenocoumarol was the most commonly found, the proportions of statin-acenocoumarol coprescriptions being roughly the same at hospital entry (11.5%) and discharge (12.4%). In 7 patients out of 69 exposed to the combination, INR was found to be higher than 3, indicating a risk of over-anticoagulation.

Conclusions

Potential statin-drug interactions are common. Although they do not differ between outpatient and inpatient settings, new hazardous coprescriptions are more frequently generated in hospital. Caution is required when acenocoumarol is coprescribed with statins, especially simvastatin.

The statin-iron nexus: anti-inflammatory intervention for arterial disease prevention

OBJECTIVES

We postulated the existence of a statin-iron nexus by which statins improve cardiovascular disease outcomes at least partially by countering proinflammatory effects of excess iron stores.

METHODS

Using data from a clinical trial of iron (ferritin) reduction in advanced peripheral arterial disease, the Iron and Atherosclerosis Study, we compared effects of ferritin levels versus high-density lipoprotein to low-density lipoprotein ratios (both were randomization variables) on clinical outcomes in participants receiving and not receiving statins.

RESULTS

Statins increased high-density lipoprotein to low-density lipoprotein ratios and reduced ferritin levels by noninteracting mechanisms. Improved clinical outcomes were associated with lower ferritin levels but not with improved lipid status.

CONCLUSIONS

There are commonalities between the clinical benefits of statins and the maintenance of physiologic iron levels. Iron reduction may be a safe and low-cost alternative to statins.

Statin medication in patients treated with antiepileptic drugs in Norway

PURPOSE

The lipid-lowering response of statins metabolized by cytochrome P450 3A4 (CYP3A4) has previously been shown to be diminished by concurrent use of enzyme-inducing antiepileptic drugs (EIAEDs). The aim of this study was to compare statin prescription in patients receiving EIAEDs versus non-enzyme-inducing antiepileptic drugs (NEIAEDs), before and after introduction of prescribing restrictions for statins in Norway.

METHODS

The Norwegian Prescription Database was used to extract data on patients using antiepileptic drugs and statins during 2004 and 2008. Statin type and dose used were compared between patients treated with at least one EIAED (i.e., carbamazepine, phenobarbital, phenytoin, primidone) and those receiving NEIAEDs only (i.e., all other antiepileptic drugs).

RESULTS

The number of included patients co-medicated with statins and AEDs was 4855 in 2004 and 9880 in 2008. Among these patients, 2827 and 3160, respectively, were treated with EIAEDs. The CYP3A4 statins (i.e., simvastatin, atorvastatin and lovastatin) accounted for 85% of all statins in 2004, increasing to 93% in 2008. There was no significant difference in the likelihood of being prescribed a CYP3A4 statin versus a non-CYP3A4 statin among patients receiving EIAEDs and NEIAEDs. The average daily dose of individual CYP3A4 statins was not different between the AED groups.

CONCLUSIONS

The present study shows that the interaction risk between CYP3A4-metabolized statins and EIAEDs is largely overlooked in Norwegian clinical practice. To avoid therapeutic failure of statin treatment in patients using AEDs, implementation of strategies for systematic management of drug interactions is warranted.

Clinical importance of the drug interaction between statins and CYP3A4 inhibitors: a retrospective cohort study in The Health Improvement Network

OBJECTIVE

To compare the relative hazard of muscle toxicity, renal dysfunction, and hepatic dysfunction associated with the drug interaction between statins and concomitant medications that inhibit the CYP3A4 isoenzyme.

BACKGROUND

Although statins provide important clinical benefits related to mitigating the risk of cardiovascular events, this class of medications also has the potential for severe adverse reactions. The risk for adverse events may be potentiated by concomitant use of medications that interfere with statin metabolism.

METHODS

Data from The Health Improvement Network (THIN) from 1990 to 2008 were used to conduct a retrospective cohort study. Cohorts were created to evaluate each outcome (muscle toxicity, renal dysfunction, and hepatic dysfunction) independently. Each cohort included new statin initiators and compared the relative hazard of the outcome. The interaction ratio (I*R) was the primary contrast of interest. The I*R represents the relative effect of each statin type (statin 3A4 substrate vs. statin non-3A4 substrate) with a CYP3A4 inhibitor, independent of the effect of the statin type without a CYP3A4 inhibitor. We adjusted for confounding variables using the multinomial propensity score.

RESULTS

The median follow-up time per cohort was 1.5 years. There were 7889 muscle toxicity events among 362,809 patients and 792,665 person-years. The adjusted muscle toxicity I*R was 1.22 (95% confidence interval [CI] = 0.90-1.66). There were 1449 renal dysfunction events among 272,099 patients and 574,584 person-years. The adjusted renal dysfunction I*R was 0.91 (95%CI = 0.58-1.44). There were 1434 hepatic dysfunction events among 367,612 patients and 815,945 person-years. The adjusted hepatic dysfunction I*R was 0.78 (95%CI = 0.45-1.31).

CONCLUSIONS

Overall, this study found no difference in the relative hazard of muscle toxicity, renal dysfunction, or hepatic dysfunction for patients prescribed a statin 3A4 substrate versus a statin non-3A4 substrate with CYP3A4 inhibitor concomitancy.

Adverse drug reactions caused by drug-drug interactions reported to Croatian Agency for Medicinal Products and Medical Devices: a retrospective observational study

Aim

To analyze potential and actual drug-drug interactions reported to the Spontaneous Reporting Database of the Croatian Agency for Medicinal Products and Medical Devices (HALMED) and determine their incidence.

Methods

In this retrospective observational study performed from March 2005 to December 2008, we detected potential and actual drug-drug interactions using interaction programs and analyzed them.

Results

HALMED received 1209 reports involving at least two drugs. There were 468 (38.7%) reports on potential drug-drug interactions, 94 of which (7.8% of total reports) were actual drug-drug interactions. Among actual drug-drug interaction reports, the proportion of serious adverse drug reactions (53 out of 94) and the number of drugs (n = 4) was significantly higher (P < 0.001) than among the remaining reports (580 out of 1982; n = 2, respectively). Actual drug-drug interactions most frequently involved nervous system agents (34.0%), and interactions caused by antiplatelet, anticoagulant, and non-steroidal anti-inflammatory drugs were in most cases serious. In only 12 out of 94 reports, actual drug-drug interactions were recognized by the reporter.

Conclusion

The study confirmed that the Spontaneous Reporting Database was a valuable resource for detecting actual drug-drug interactions. Also, it identified drugs leading to serious adverse drug reactions and deaths, thus indicating the areas which should be in the focus of health care education.

Epidemiology and characteristics of adverse drug reactions caused by drug-drug interactions

INTRODUCTION

Drug-drug interactions (DDIs) arise in numerous different ways, involving pharmacokinetic or pharmacodynamic mechanisms. Adverse drug reactions are a possible consequence of DDIs and health operators are often unaware of the clinical risks of certain drug combinations. Many papers on drug interactions have been published in recent years, but most of them focused on potential DDIs while few studies have been conducted on actual interactions.

AREAS COVERED

This paper reviews the epidemiology of actual DDIs in outpatients as well as in hospital settings and in spontaneous reporting databases. The incidence of actual DDIs is consistently lower than that of potential DDIs. However, the absolute number of patients involved is high, representing a significant proportion of adverse drug reactions. The importance of risk factors such as age, polypharmacy and genetic polymorphisms is also evaluated. The relevance and efficacy of tools for recognizing and preventing DDIs are discussed.

EXPERT OPINION

Potential DDIs far outnumber actual drug interactions. The potential for an adverse interaction to occur is often theoretical, and clinically important adverse effects occur only in the presence of specific risk factors. Several studies have shown the efficacy of computers in early detection of DDIs. However, a correct risk-benefit evaluation by the prescribing physician, together with a careful clinical, physiological and biochemical monitoring of patients, is essential. Future directions of drug interaction research include the increasing importance of pharmacogenetics in preventing DDIs and the evaluation of interactions with biological drugs.

Prodrugs--from serendipity to rational design

The prodrug concept has been used to improve undesirable properties of drugs since the late 19th century, although it was only at the end of the 1950s that the actual term prodrug was introduced for the first time. Prodrugs are inactive, bioreversible derivatives of active drug molecules that must undergo an enzymatic and/or chemical transformation in vivo to release the active parent drug, which can then elicit its desired pharmacological effect in the body. In most cases, prodrugs are simple chemical derivatives that are only one or two chemical or enzymatic steps away from the active parent drug. However, some prodrugs lack an obvious carrier or promoiety but instead result from a molecular modification of the prodrug itself, which generates a new active compound. Numerous prodrugs designed to overcome formulation, delivery, and toxicity barriers to drug utilization have reached the market. In fact, approximately 20% of all small molecular drugs approved during the period 2000 to 2008 were prodrugs. Although the development of a prodrug can be very challenging, the prodrug approach represents a feasible way to improve the erratic properties of investigational drugs or drugs already on the market. This review introduces in depth the rationale behind the use of the prodrug approach from past to present, and also considers the possible problems that can arise from inadequate activation of prodrugs.

Effect of pregnane X receptor (PXR) prototype agonists on chemoprotective and drug metabolizing enzymes in mice

The effects of known PXR inducers; spironolactone [SPL, (i.p.)], pregnenolone-16 alpha-carbonitrile [PCN, (i.g.)] and dexamethasone (i.p.) on hepatic drug metabolizing enzymes in the male CF1 mouse were examined 24 h after 3 daily doses (50, 100, or 200 mg/kg) in corn oil vehicle. All three compounds produced dose-dependent elevations in cytochrome P450 [CYP3A], glutathione S-transferase [GST] and NAD(P)H quinone oxidoreductase [NQO] activities. Only elevations in CYP3A produced after dexamethasone were statistically significant. An elevation in microsomal epoxide hydrolase [mEH, Ephx1] activity was seen after almost all treatments but was erratic with dose. UDP-glucuronosyltransferase and thioredoxin reductase activities were not increased by any agent. Dexamethasone elevated Cyp1a1/2 mRNA at the low dose but reduced the mRNA transcript and activity of the enzyme at the mid and high doses. The mRNA responses of Ephx1 and Nqo1 showed a close parallel to each other with no increases after dexamethasone or SPL treatment, and elevations at the mid dose of PCN. With the exception of dexamethasone at the high dose, elevations in Gst mRNAs were seen with all doses of the three agents. When a large number of hepatic enzymes are examined, the responses to dexamethasone, SPL and PCN are far from identical, and any dose dependency is agent specific. Induction of enzymes seems more complicated to be controlled by one orphan receptor. This study not only filled the void about the murine PXR-induction profile but also will help in the course of drug development research with respect to extrapolation to human risk assessment.