Pharmacokinetic drug interaction profile of omeprazole with adverse consequences and clinical risk management

Helicobacter pylori Eradication Treatment in Older Patients

Helicobacter pylori is the main etiopathogenetic factor of chronic gastritis, peptic ulcer disease and gastric cancer. The world's population is shifting towards older people, who have the highest prevalence of H. pylori. Aging-related peculiarities could have an impact on the treatment of H. pylori and there is still a lack of research data in the older population. The aim of this review was to summarize the findings of the most recent information, publications and studies on the issues relating to H. pylori infection in older patients. H. pylori eradication offers gastrointestinal and extra gastrointestinal benefits in older patients. Based on the main guidelines, H. pylori should be eradicated independent of the patient's age, only reconsidering cases with terminal illness and low life expectancy. Proton pump inhibitors are generally safe and well tolerated. Some antibiotics require dose adjustment only in advanced renal insufficiency and the risk of hepatotoxicity is very low. Special precautions should be taken in patients with polypharmacy and those taking aspirin or non-steroidal anti-inflammatory drugs. In older patients, H. pylori eradication treatment frequently causes only mild and short-term adverse events; however, treatment compliance is usually still very good. H. pylori treatment in older patients does not increase the risk of Clostridium difficile infection. Optimal eradication effectiveness (> 90%) is mostly achieved with bismuth- and non-bismuth-based quadruple therapies. Susceptibility-guided treatment of H. pylori can contribute to increasing the effectiveness of eradication regimens in older adults. To achieve optimal H. pylori eradication effectiveness in older patients, the same guidelines, which are applied to adults, also apply to this population: avoiding repetitive treatment prescriptions, choosing quadruple therapies, prescribing longer treatment duration and administering high-dose proton pump inhibitors twice daily.

Simultaneous Determination of Loratadine and Its Metabolite Desloratadine in Beagle Plasma by LC-MS/MS and Application for Pharmacokinetics Study of Loratadine Tablets and Omeprazole‑Induced Drug-Drug Interaction

Background

Loratadine (LTD) is a Biopharmaceutical Classification System II basic drug with pH-sensitive aqueous solubility and dissolution is a speed-limiting step of its absorption. The drug dissolution and the gastrointestinal tract pH conditions are likely to influence the in vivo pharmacokinetic behavior of LTD tablets.

Materials and Method

A rapid, sensitive, and reliable bioanalytical method for simultaneous quantitation of LTD and its active metabolite desloratadine (DL) in beagle plasma was developed and validated based on liquid chromatography tandem mass spectrometry (LC-MS/MS). Sample preparation in low plasma consumption was accomplished by liquid–liquid extraction. The chromatographic separation was achieved on a Phenomenex Kinetex C8 column using acetonitrile and 5 mM ammonium formate as the mobile phase. A comparative pharmacokinetics study of three LTD tablets with different dissolution rates was conducted in male beagles in fasting state and an omeprazole-induced drug–drug interaction (DDI) study was subsequently performed under pretreatment of omeprazole.

Results and Conclusion

The method showed a good linear correlation over the concentration ranges of 0.008–24 ng/mL for LTD and 0.8–800 ng/mL for DL, and was successfully applied to analyze the two compounds in beagle plasma. Pharmacokinetic results showed in the fasting state the three LTD tablets were equivalent in beagles in terms of effective components. DL of the three tablets were equivalent, indicating metabolite was less susceptible to pharmaceutic preparation factors for LTD tablets in beagles. Moreover, significant changes in LTD and DL pharmacokinetics parameters were observed under the effect of omeprazole-induced pH increase in gastrointestinal tract, suggesting that DDI effects are of concern for the curative effect of LTD when combined with omeprazole. The findings will contribute to the future pharmaceutical preparations research as well as the clinical application of LTD.

Drug-drug interactions in polypharmacy patients: The impact of renal impairment

Chronic kidney disease (CKD) is a long-term condition characterized by a gradual loss of kidney functions, usually accompanied by other comorbidities including cardiovascular diseases (hypertension, heart failure and stroke) and diabetes mellitus. Therefore, multiple pharmacological prescriptions are very common in these patients. Epidemiological and clinical observations have shown that polypharmacy may increase the probability of adverse drug reactions (ADRs), possibly through a higher risk of drug-drug interactions (DDIs). Renal impairment may further worsen this scenario by affecting the physiological and biochemical pathways underlying pharmacokinetics and ultimately modifying the pharmacodynamic responses. It has been estimated that the prevalence of DDIs in CKD patients ranged between 56.9% and 89.1%, accounting for a significant increase in healthcare costs, length and frequency of hospitalization, with a detrimental impact on health and quality of life of these patients. Despite these recognized high-risk conditions, scientific literature released on this topic is still limited. Basing on the most commonly prescribed therapies in patients with CKD, the present short review summarizes the current state of knowledge of the putative DDIs occurring in CKD patients undergoing polytherapy. The most relevant underlying mechanisms and their clinical significance are also debated.

The Influence of Omeprazole on the Dissolution Processes of pH-Dependent Magnetic Tablets Assessed by Pharmacomagnetography

Pharmacomagnetography involves the simultaneous assessment of solid dosage forms (SDFs) in the human gastrointestinal (GI) tract and the drug plasmatic concentration, using a biomagnetic technique and pharmacokinetics analysis. This multi-instrumental approach helps the evaluation, as GI variables can interfere with the drug delivery processes. This study aimed to employ pharmacomagnetography to evaluate the influence of omeprazole on the drug release and absorption of metronidazole administered orally in magnetic-coated tablets. Magnetic-coated tablets, coated with Eudragit^® E-100 (E100) and containing 100 mg of metronidazole, were produced. For the in vivo experiments, 12 volunteers participated in the two phases of the study (placebo and omeprazole) on different days to assess the bioavailability of metronidazole. The results indicated a shift as the pH of the solution increased and a delay in the dissolution of metronidazole, showing that the pH increase interferes with the release processes of tablets coated with E100. Our study reinforced the advantages of pharmacomagnetography as a tool to perform a multi-instrumental correlation analysis of the disintegration process and the bioavailability of drugs.

Oral itraconazole for epistaxis in hereditary hemorrhagic telangiectasia: a proof of concept study

The inhibiting effects of itraconazole, an antifungal drug on vascular endothelial growth factor (VEGF) have recently been discovered. By inhibiting VEGF, itraconazole has shown potential in clinical trials as anti-cancer treatment. In hereditary hemorrhagic telangiectasia (HHT) patients, VEGF levels are elevated and inhibition of VEGF can decrease bleeding. Itraconazole could potentially serve as anti-angiogenic therapy for HHT-related bleeding. We report a proof of concept study with HHT patients and severe epistaxis. Patients were treated with daily 200 mg orally administered itraconazole for sixteen weeks. Twenty-one HHT patients, 8 females (38%), 13 males (62%), median age of 59 years (interquartile range (IQR) 55-69) were enrolled. Of these patients, 13 (62%) were diagnosed with HHT type 1, seven (33%) with HHT type 2 and in one patient (5%), no pathognomonic HHT mutation was found. Four patients (19%) prematurely terminated the study (3 due to mild or moderate side-effects) resulting in 17 patients included in the analyses. The median epistaxis severity score significantly decreased during treatment from 6.0 (IQR 5.1-7.2) to 3.8 (IQR 3.1-5.2) (p = 0.006). The monthly epistaxis frequency decreased from 56 to 38 epistaxis episodes (p = 0.004) and the monthly duration from 407 to 278 minutes (p = 0.005). Hemoglobin levels did not significantly change. The quality of life showed a small but significant improvement. In conclusion, oral itraconazole significantly improved epistaxis in HHT patients. The potential benefit of itraconazole in HHT should be further investigated.

The impact of omeprazole on mycophenolate pharmacokinetics in kidney transplant recipients

Background

The absorption rates of mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS) may be influenced by the concomitant use of omeprazole.

Methods

One hundred kidney transplant patients were recruited during their outpatient visits, including 50 on MMF and 50 on EC-MPS. At the clinic, a predose mycophenolic acid (MPA) sample (C0) was collected; subsequently, the participants received the proton-pump inhibitor omeprazole along with either MMF or EC-MPS. Two more blood samples were collected at 1.5 and 3.5 hours and used to estimate an area under the curve (AUC) from zero to 12 hours [AUC (0-12)].

Results

The mean number of months after transplant was 92 months. The median AUC (0-12) and C0 results were 62.2 mg·h/L and 2.0 mg/L for the MMF group and 71.9 mg·h/L and 1.8 mg/L for the EC-MPS group (P = 0.160 and 0.225, respectively). Interestingly, 54% of the MMF group and 62% of the EC-MPS group showed AUCs above the target values. The correlation between MPA C0 and the predicted AUC was poor in both groups.

Conclusion

Omeprazole can be safely co-administered with either MMF or EC-MPS, as it did not compromise the MPA exposure. Unexpectedly, however, a high percentage of patients presented MPA AUCs exceeding the target value, highlighting the importance of periodically assessing MPA level.

Tacrolimus blood concentration increase depends on administration route when combined with voriconazole in pediatric stem cell transplant recipients

BACKGROUND

Understanding of TAC pharmacokinetics is required to avoid both overdosing and underdosing. VRCZ is known to increase the TAC blood concentration by inhibiting CYP3A4; however, detailed, practical information on pediatric cases is still scarce. Herein, we investigated the association between the TAC blood concentration and dosage focusing on the administration route and concomitant use of VRCZ in children.

METHODS

In total, 38 children who received TAC during stem cell transplantation at our hospital between January 2013 and April 2018 were included. The ratio of the TAC blood concentration (ng/mL) to dosage (mg/kg/day) (C/D) was calculated at the last continuous intravenous infusion (C/Div) and after switching to oral administration (C/Dpo).

RESULTS

Patients with VRCZ (n = 14) showed a higher C/D regardless of administration route (median C/Div: with VRCZ/without VRCZ = 832/643, median C/Dpo: with VRCZ/without VRCZ = 339/45). Additionally, the (C/Div)/(C/Dpo) was about one-fourth in cases with VRCZ; the median (C/Div)/(C/Dpo) was 3.3 for cases with VRCZ and 13.5 for cases without VRCZ. Interestingly, the increase in the TAC blood concentration due to VRCZ was higher when TAC was administered orally, especially in adolescent patients.

CONCLUSIONS

To obtain an optimal TAC blood concentration, dose adjustment based on multiple factors, such as administration route, concomitant use of VRCZ, and age, is required.

Factors Influencing the Safety and Efficiency of Antifungal Prophylaxis with Posaconazole in Children with Hematological Diseases: From Genetics to Polypharmacotherapy

The aim of this study was to determine the impact of ABCB1 polymorphism, BMI, age and drug co-administration on safety and efficiency of posaconazole (PCZ) oral suspension treatment in children with hematological diseases. Seventy children were included in the study. ABCB1 polymorphism in fifty-eight children was determined using a PCR–RFLP method. A protocol with data on the health condition, treatment and adverse events (AE), as well as a survey on treatment tolerance for the legal guardians was evaluated. Liver function tests were observed for the first 20 days, and AE during the complete medication period. For statistical analysis a χ² test with Yates’s correction, a Pearson’s or Spearman’s correlation test was performed (p < 0.05). Genetic testing showed 24% CC, 46% CT and 30% of TT variants. PCZ prophylaxis failed in twenty cases, where change in prophylactic treatment was needed. Fifty-two children suffered from at least one mild to moderate adverse event. Sixty-five legal guardians completed the survey, most of them reported the treatment to be well tolerated. ABCB1 polymorphism had no impact on AE occurrence and posaconazole prophylaxis efficiency. Age influenced the number of gastrointestinal (p = 0.02), visual (p = 0.05), neurological (p = 0.01), dermatological (p = 0.002) and flu-like (p = 0.02) complications. AST (p = 0.03) and LDH (p = 0.008) activity presented age dependency. The concomitant use of proton pump inhibitors (PPI) had impact on liver health parameters elevation (p = 0.009) and circulatory system complications (p = 0.008). High incidence of mild to moderate AE, and other factors influencing PCZ pharmacokinetics (PPI co-administration, obesity), suggest a need for careful pediatric onco-hematology patient evaluation.

Management options for low-dose methotrexate-induced oral ulcers: A systematic review

Background

Oral ulcers caused by methotrexate (MTX) at low doses are a known side effect of this drug. Although increasingly more patients are medicated with MTX, these painful ulcers, without traumatic origin and resistant to any type of treatment, are not usually identified by health professionals as a side effect of the medication.

Material and Methods

In the absence of a consensus protocol for the effective treatment of oral lesions produced by MTX, the objective of this article was to review and analyse the information from articles related to oral ulcers produced by low-dose MTX and to record the clinical management performed and the MTX dose given to the patient. Data sources - Medline, Web of Science, and Cochrane Library. Participants - Patients treated with low-dose MTX (less than 25 mg/week). Interventions - Management of oral lesions caused by MTX. Study eligibility criterion, study appraisal and synthesis method: An initial search was carried out in the aforementioned databases with the terms ‘methotrexate AND oral OR ulcer’. The search was carried out using both medical subject heading (MeSH) terms and a free search between January 2003 and January 2018. Of the results obtained, two independent researchers analysed abstracts that met the search criteria, that is, those that mentioned oral ulcers produced by MTX at low doses. Next, both researchers read the complete article and determined whether it met the following inclusion criteria: written in English, specified the dose of MTX prescribed for the patient and specified the protocol of action for the ulcers. A third investigator acted as a mediator in cases of dispute. Agreement was calculated using Cohen’s kappa coefficient, with a k value of 0.82. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guide for systematic reviews was used.

Results

The initial search resulted in a total of 66 articles, of which 30 were selected to assess their inclusion in this study. Finally, 16 met the inclusion criteria. Using the Pierson and Newcastle-Ottawa scales and Bradford Hill criteria modified for studies of case series and “in relation to a case”, 2 were rated as high quality, 2 were rated as low quality and 12 were rated as medium quality. The limitations of this study are based on the fact that all of the articles available to carry out the systematic review were “in relation to a case or series of cases”, with the heterogeneity of data that this implies.

Conclusions

Evidence on the management of oral ulcers in the oral cavity produced by MTX at low doses is scarce due to the heterogeneity of data and the measures adopted in the selected studies. Therefore, it seems that this management is relegated to the perception of the clinician rather than to a specific protocol of action. Studies with a longer follow-up duration and larger sample size are needed to guide different health professionals on the management of these lesions.

Key words:Methotrexate, Oral ulcers, Low-dose methotrexate.

Proton Pump Inhibitors and Dementia: Physiopathological Mechanisms and Clinical Consequences

Alzheimer's disease (AD) is the most common type of dementia, mainly encompassing cognitive decline in subjects aged ≥65 years. Further, AD is characterized by selective synaptic and neuronal degeneration, vascular dysfunction, and two histopathological features: extracellular amyloid plaques composed of amyloid beta peptide (Aβ) and neurofibrillary tangles formed by hyperphosphorylated tau protein. Dementia and AD are chronic neurodegenerative conditions with a complex physiopathology involving both genetic and environmental factors. Recent clinical studies have shown that proton pump inhibitors (PPIs) are associated with risk of dementia, including AD. However, a recent case-control study reported decreased risk of dementia. PPIs are a widely indicated class of drugs for gastric acid-related disorders, although most older adult users are not treated for the correct indication. Although neurological side effects secondary to PPIs are rare, several preclinical reports indicate that PPIs might increase Aβ levels, interact with tau protein, and affect the neuronal microenvironment through several mechanisms. Considering the controversy between PPI use and dementia risk, as well as both cognitive and neuroprotective effects, the aim of this review is to examine the relationship between PPI use and brain effects from a neurobiological and clinical perspective.

Opioid analgesics-related pharmacokinetic drug interactions: from the perspectives of evidence based on randomized controlled trials and clinical risk management

BACKGROUND

Multimorbidity results in complex polypharmacy which may bear a risk of drug interactions. A better understanding of opioid analgesics combination therapy used for pain management could help warrant medication safety, efficacy, and economic relevance. Until now there has been no review summarizing the opioid analgesics-related pharmacokinetic drug interactions from the perspective of evidence based on randomized controlled trials (RCTs).

METHOD

A literature search was performed using PubMed, MEDLINE, and the Cochrane Library, using a PRISMA flowchart.

RESULTS

Fifty-two RCTs were included for data interpretation. Forty-two RCTs (80.8%) were conducted in healthy volunteers, whereas 10 RCTs (19.2%) enrolled true patients. None of the opioid-drug/herb pairs was listed as contraindications of opioids involved in this review. Circumstances in which opioid is comedicated as a precipitant drug include morphine-P2Y12 inhibitors, morphine-gabapentin, and methadone-zidovudine. Circumstances in which opioid is comedicated as an object drug include rifampin-opioids (morphine, tramadol, oxycodone, methadone), quinidine-opioids (morphine, fentanyl, oxycodone, codeine, dihydrocodeine, methadone), antimycotics-opioids (buprenorphine, fentanyl, morphine, oxycodone, methadone, tilidine, tramadol), protease inhibitors-opioids (ritonavir, ritonavir/lopinavir-oxycodone, ritonavir-fentanyl, ritonavir-tilidine), grapefruit juice-opioids (oxycodone, fentanyl, methadone), antidepressants-opioids (paroxetine-tramadol, paroxetine-hydrocodone, paroxetine-oxycodone, escitalopram-tramadol), metoclopramide-morphine, amantadine-morphine, sumatriptan-butorphanol nasal sprays, ticlopidine-tramadol, St John's wort-oxycodone, macrolides/ketolides-oxycodone, and levomepromazine-codeine. RCTs investigating the same combination, almost unanimously, drew consistent conclusions, except two RCTs on amantadine-intravenous morphine combination where a different amantadine dose was used and two RCTs on morphine-ticagrelor combination where healthy volunteers and true patients were enrolled, respectively. RCTs investigating in true patients may reflect a realistic clinical scenario and overcome the limitation of RCTs performed in healthy volunteers under standardized conditions. Further research opportunities are also presented in this review.

CONCLUSION

Effective and safe combination therapy of opioids can be achieved by promoting the awareness of potential changes in therapeutic efficacy and toxicities, prescribing alternatives or changing administration strategy, tailoring dose, reviewing the appropriateness of orders, and paying attention to medication monitoring.

Therapeutic Risk and Benefits of Concomitantly Using Herbal Medicines and Conventional Medicines: From the Perspectives of Evidence Based on Randomized Controlled Trials and Clinical Risk Management

Despite increased awareness of the potential of herb-drug interactions (HDIs), the lack of rigorous clinical evidence regarding the significance provides a challenge for clinicians and consumers to make rational decisions about the safe combination of herbal and conventional medicines. This review addressed HDIs based on evidence from randomized controlled trials (RCTs). Literature was identified by performing a PubMed search till January 2017. Risk description and clinical risk management were described. Among 74 finally included RCTs, 17 RCTs (22.97%) simply addressed pharmacodynamic HDIs. Fifty-seven RCTs (77.03%) investigated pharmacokinetic HDIs and twenty-eight of them showed potential or actual clinical relevance. The extent of an HDI may be associated with the factors such as pharmacogenomics, dose of active ingredients in herbs, time course of interaction, characteristics of the object drugs (e.g., administration routes and pharmacokinetic profiles), modification of herbal prescription compositions, and coexistence of inducers and inhibitors. Clinical professionals should enhance risk management on HDIs such as increasing awareness of potential changes in therapeutic risk and benefits, inquiring patients about all currently used conventional medicines and herbal medicines and supplements, automatically detecting highly substantial significant HDI by computerized reminder system, selecting the alternatives, adjusting dose, reviewing the appropriateness of physician orders, educating patients to monitor for drug-interaction symptoms, and paying attention to follow-up visit and consultation.

Patient-centered Outcomes with Concomitant Use of Proton Pump Inhibitors and Other Drugs

PURPOSE

We performed a systematic review of patient-centered outcomes after the concomitant use of proton pump inhibitors (PPIs) and other drugs.

METHODS

We searched 4 databases in July 2016 to find studies that reported mortality and morbidity after the concomitant use of PPIs and other drugs. We conducted direct meta-analyses using a random-effects model and graded the quality of evidence according to the Grading of Recommendations Assessment, Development and Evaluation working group approach.

FINDINGS

We included data from 17 systematic reviews and meta-analyses, 16 randomized controlled trials, and 16 observational studies that examined the concomitant use of PPIs with medications from 10 drug classes. Low-quality evidence suggests that the use of PPIs is associated with greater morbidity when administered with antiplatelet drugs, bisphosphonates, antibiotics, anticoagulants, metformin, mycophenolate mofetil, or nelfinavir. Concomitant PPIs reduce drug-induced gastrointestinal bleeding and are associated with greater docetaxel and cisplatin response rates in patients with metastatic breast cancer. For demonstrated statistically significant relative risks and benefits from concomitant PPIs, the magnitudes of the effects are small, with <100 attributable events per 1000 patients treated, and the effects are inconsistent among specific drugs. Among individual PPIs, the concomitant use of pantoprazole or esomeprazole, but not omeprazole or lansoprazole, is associated with an increased risk for all-cause mortality, nonfatal myocardial infarction, or stroke. Clopidogrel is associated with a greater risk for myocardial infarction compared with prasugrel. Conflicting results between randomized controlled trials and observational studies and high risk for bias in the body of evidence lessened our confidence in the results.

IMPLICATIONS

Available evidence suggests a greater risk for adverse patient outcomes after the concomitant use of PPIs and medications from 9 drug classes and warns against inappropriate drug combinations.

The compelling case for therapeutic drug monitoring of mycophenolate mofetil therapy

We have reviewed current evidence on the therapeutic drug monitoring (TDM) of mycophenolic acid (MPA) in relationship to drug efficacy and safety. The relationship between actual MPA exposure and mycophenolate mofetil (MMF) dose has been shown to be weak in children and adolescents. The TDM of MPA exposure should ideally be performed using full pharmacokinetic profiles or limited sampling strategies. Recent evidence has provided some rationale for using the post-dose trough level as a single measure. In terms of short-term efficacy, there is strong evidence that a MPA area under the time-concentration curve of >30 mg × h/L reduces acute rejection episodes early after renal transplantation, and there is evolving evidence that aiming for the same exposure over the long term may be a viable strategy to reduce the formation of donor-specific antibodies. Strong evidence also supports the existence of important drug interactions and age/developmental dependent differences in drug metabolism that may necessitate the need for TDM of MMF therapy. Based on these findings and given the substantial inter- and intra-patient variability of MPA exposure, it would appear that MMF therapy should be subject to TDM to avoid over- and under-dosing. This may be a viable strategy to reduce treatment-emergent adverse events and to increase the effective pediatric transplant survival rates.

Proton Pump Inhibitors and the Prescribing Cascade

ACTIVITY OBJECTIVES: 1. Describe the prescribing cascade of proton pump inhibitors (PPI) in nursing home residents. 2. Identify the statistically significant factors related to the use of PPI and H2 receptor blockers. DISCLOSURE STATEMENT Neither the planners nor the authors have any conflicts of interest to disclose. The current study examined the use of proton pump inhibitor (PPI) drugs in 248 nursing home residents and factors associated with being prescribed a PPI. Ninety-three percent of residents taking a PPI had done so for longer than recommended durations. As anticholinergic burden, vitamin/supplement use, and number of oral products taken daily increased, residents were more likely to be taking a PPI. Higher anticholinergic burden (p = 0.031) and number of oral products taken daily (p = 0.04) were two statistically significant predictors in the final logistic regression model. Significant predictors of PPI use in the current study may be explained by the association between polypharmacy and dyspepsia and the lowering of esophageal sphincter pressure by anticholinergic drugs. High use of PPIs in nursing home residents may represent a prescribing cascade.

Pharmacokinetic drug interactions with clopidogrel: updated review and risk management in combination therapy

Background

Coprescribing of clopidogrel and other drugs is common. Available reviews have addressed the drug–drug interactions (DDIs) when clopidogrel is as an object drug, or focused on combination use of clopidogrel and a special class of drugs. Clinicians may still be ignorant of those DDIs when clopidogrel is a precipitant drug, the factors determining the degree of DDIs, and corresponding risk management.

Methods

A literature search was performed using PubMed, MEDLINE, Web of Science, and the Cochrane Library to analyze the pharmacokinetic DDIs of clopidogrel and new P2Y₁₂ receptor inhibitors.

Results

Clopidogrel affects the pharmacokinetics of cerivastatin, repaglinide, ferulic acid, sibutramine, efavirenz, and omeprazole. Low efficacy of clopidogrel is anticipated in the presence of omeprazole, esomeprazole, morphine, grapefruit juice, scutellarin, fluoxetine, azole antifungals, calcium channel blockers, sulfonylureas, and ritonavir. Augmented antiplatelet effects are anticipated when clopidogrel is coprescribed with aspirin, curcumin, cyclosporin, St John’s wort, rifampicin, and angiotensin-converting enzyme inhibitors. The factors determining the degree of DDIs with clopidogrel include genetic status (eg, cytochrome P540 [CYP]2B6*6, CYP2C19 polymorphism, CYP3A5*3, CYP3A4*1G, and CYP1A2-163C.A), species differences, and dose strength. The DDI risk does not exhibit a class effect, eg, the effects of clopidogrel on cerivastatin versus other statins, the effects of proton pump inhibitors on clopidogrel (omeprazole, esomeprazole versus pantoprazole, rabeprazole), the effects of rifampicin on clopidogrel versus ticagrelor and prasugrel, and the effects of calcium channel blockers on clopidogrel (amlodipine versus P-glycoprotein-inhibiting calcium channel blockers). The mechanism of the DDIs with clopidogrel involves modulating CYP enzymes (eg, CYP2B6, CYP2C8, CYP2C19, and CYP3A4), paraoxonase-1, hepatic carboxylesterase 1, P-glycoprotein, and organic anion transporter family member 1B1.

Conclusion

Effective and safe clopidogrel combination therapy can be achieved by increasing the awareness of potential changes in efficacy and toxicity, rationally selecting alternatives, tailoring drug therapy based on genotype, checking the appropriateness of physician orders, and performing therapeutic monitoring.

Pharmacokinetic drug-drug interactions between 1,4-dihydropyridine calcium channel blockers and statins: factors determining interaction strength and relevant clinical risk management

Background

Coadministration of 1,4-dihydropyridine calcium channel blockers (DHP-CCBs) with statins (or 3-hydroxy-3-methylglutaryl-coenzyme A [HMG-CoA] reductase inhibitors) is common for patients with hypercholesterolemia and hypertension. To reduce the risk of myopathy, in 2011, the US Food and Drug Administration (FDA) Drug Safety Communication set a new dose limitation for simvastatin, for patients taking simvastatin concomitantly with amlodipine. However, there is no such dose limitation for atorvastatin for patients receiving amlodipine. The combination pill formulation of amlodipine/atorvastatin is available on the market. There been no systematic review of the pharmacokinetic drug–drug interaction (DDI) profile of DHP-CCBs with statins, the underlying mechanisms for DDIs of different degree, or the corresponding management of clinical risk.

Methods

The relevant literature was identified by performing a PubMed search, covering the period from January 1987 to September 2013. Studies in the field of drug metabolism and pharmacokinetics that described DDIs between DHP-CCB and statin or that directly compared the degree of DDIs associated with cytochrome P450 (CYP)3A4-metabolized statins or DHP-CCBs were included. The full text of each article was critically reviewed, and data interpretation was performed.

Results

There were three circumstances related to pharmacokinetic DDIs in the combined use of DHP-CCB and statin: 1) statin is comedicated as the precipitant drug (pravastatin–nimodipine and lovastatin–nicardipine); 2) statin is comedicated as the object drug (isradipine–lovastatin, lacidipine–simvastatin, amlodipine–simvastatin, benidipine-simvastatin, azelnidipine– simvastatin, lercanidipine–simvastatin, and amlodipine–atorvastatin); and 3) mutual interactions (lercanidipine–fluvastatin). Simvastatin has an extensive first-pass effect in the intestinal wall, whereas atorvastatin has a smaller intestinal first-pass effect. The interaction with simvastatin seems mainly driven by CYP3A4 inhibition at the intestinal level, whereas the interaction with atorvastatin is more due to hepatic CYP3A4 inhibition. The interaction of CYP3A4 inhibitor with simvastatin has been more pronounced compared with atorvastatin. From the current data, atorvastatin seems to be a safer CYP3A4-statin for comedication with DHP-CCB. There is no convincing evidence that amlodipine is an unusual DHP-CCB, either as a precipitant drug or as an object drug, from the perspective of CYP3A4-mediated drug metabolism. Amlodipine may have interactions with CYP3A5 in addition to CYP3A4, which may explain its particular characteristics in comparison with other DHP-CCBs. The degree of DDIs between the DHP-CCB and statin and the clinical outcome depends on many factors, such as the kind of statin, physicochemical proprieties of the DHP-CCB, the dose of either the precipitant drug or the object drug, the sex of the patient (eg, isradipine–lovastatin), route of drug administration (eg, oral versus intravenous nicardipine–lovastatin), the administration schedule (eg, nonconcurrent dosing method versus concurrent dosing method), and the pharmacogenetic status (eg, CYP3A5-nonexpressers versus CYP3A5-expressers).

Conclusion

Clinical professionals should enhance risk management regarding the combination use of two classes of drugs by increasing their awareness of the potential changes in therapeutic efficacy and adverse drug reactions, by rationally prescribing alternatives, by paying attention to dose adjustment and the administration schedule, and by review of the appropriateness of physician orders. Further study is needed – the DDIs between DHP-CCBs and statins have not all been studied in humans, from either a pharmacokinetic or a clinical perspective; also, the strength of the different pharmacokinetic interactions of DHP-CCBs with statins should be addressed by systematic investigations.