Antihypertensive therapy: special focus on drug interactions

Drug Interactions with Antihypertensives

PURPOSE OF REVIEW

Hypertension is remarkably prevalent, affecting an estimated 1.13 billion people worldwide. It often requires the use of multi-drug regimens and is commonly associated with a myriad of other comorbidities which increase medication use. The pervasive use of antihypertensive medications combined with the presence of polypharmacy in many hypertensive patients results in significant risk of drug interactions. This review will summarize the relevant literature to assist clinicians in mitigating drug interaction risks when prescribing antihypertensives.

RECENT FINDINGS

Pharmacokinetic interactions affect drug disposition in the body and can occur at the steps of absorption, distribution, metabolism, or elimination of involved medications. Data has established the calcium channel blockers, namely, diltiazem and verapamil, as potent inhibitors of CYP3A4, and the majority of significant drug interactions involving antihypertensives are attributable to these two agents. Although less common, pharmacokinetic drug interactions with other antihypertensive classes have also been identified. Pharmacodynamic drug interactions with antihypertensives lead to synergy or antagonism of blood pressure lowering effects and can increase or mitigate adverse effects depending on the agents involved. Knowledge is emerging about drug-induced phenoconversion, a phenomenon whereby a drug interaction results in a drug metabolizing phenotype that is different than that predicted by an individual's genotype. Antihypertensive use in patients with comorbidities and polypharmacy increases the likelihood of encountering important drug-drug interactions. Dedicated efforts to better understand the relationship between pharmacokinetic drug interactions and pharmacogenomic information is important to advance efforts related to personalized medicine.

Effects of Ramadan fasting on anthropometric measures, blood pressure, and lipid profile among hypertensive patients in the Kurdistan region of Iraq

Objective

This study was employed to assess the effects of Ramadan fasting on anthropometric measures, blood pressure, and lipid profile among hypertensive patients.

Method

This cross-sectional study was conducted among a representative sample, which was selected using a census survey of hypertensive patients (both gender, aged 25-50 years, on regular antihypertensive drugs (atenolol: 50 mg orally once a day)), during Ramadan month that was falling in April to May 2020. The patients were receiving care at Halabja hospital in the Kurdistan region of Iraq. All patients were assessed in two phase's baseline (a week before Ramadan) and end stage (a week after Ramadan), using anthropometric indices, physical examination, biochemical tests, and a structured questionnaire. Statistical analysis was performed using SPSS version 21.

Results

A total of 120 hypertensive patients were included in the study (50% females and 50% males), with a mean age of 37.5 ± 6.6 years. The major finding of our study was the significant decrease in blood pressure (P < 0.001). Furthermore, the body weight, body mass index, and waist circumference of the participants decreased after Ramadan fasting in a significant approach (P < 0.001 for all). However, for the lipid profile components, the total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol change persisted not statistically significant (P > 0.05), while only triglyceride decreased drastically after Ramadan fasting (P < 0.001).

Conclusion

Ramadan fasting could contribute in the improvement of blood pressure and lowers triglyceride levels, body weight, body mass index, and waist circumference of adult hypertensive patients.

Concomitant drugs with low risks of drug-drug interactions for use in oncology clinical trials

BACKGROUND

Drug-drug interactions (DDIs) may occur with investigational drugs and affect patient safety, trial outcomes, and drug development. A list of preferred drugs with minimal risks of DDIs for treatment of symptoms or comorbidities frequently encountered by cancer patients would be helpful.

METHODS

We reviewed the literature to assess DDIs reported for the main drugs available for treatment of symptoms/comorbidities frequently encountered by cancer patients. Reviews and relevant original articles cited were retrieved and analyzed, and the following data were collected and double-checked: pharmacological properties; effects, if any, of drugs on CYP enzymes, membrane transporters, and QT interval; and involvement in significant DDIs.

RESULTS

A list of preferred drugs with minimal risks of DDIs was compiled.

CONCLUSION

Acknowledging for heterogeneity in data sources, prevention of unexpected DDIs during clinical trials may be improved by using this list of preferred drugs for the management of study patient's symptoms.

Non-steroidal anti-inflammatory drugs (NSAIDs) and hypertension treatment intensification: a population-based cohort study

PURPOSE

Non-steroidal anti-inflammatory drugs (NSAIDs) are known to antagonize the effects of antihypertensive drugs, and these associations can lead to an increase in arterial blood pressure. However, the impact of NSAIDs on hypertension treatment management in large-scale populations remains poorly evaluated. We examined whether the introduction of NSAID into the treatment regimen would induce an intensification of hypertension treatment (defined as the introduction of a new antihypertensive drug).

METHODS

We conducted a cohort study involving 5,710 hypertensive subjects included in the French health insurance system database who had been treated and stabilized with their antihypertensive therapy and not exposed to any NSAID between 1 April 2005 and 1 April 2006. The maximum follow-up duration was 4 years.

RESULTS

Adjusted hazard ratios (HR) for hypertension treatment intensification were 1.34 [95 % confidence interval (CI) 1.05-1.71] for NSAIDs in general, 1.79 (95 % CI 1.15-2.78) for diclofenac and 2.02 (95 % CI:1.09-3.77) for piroxicam. There were significant interactions between NSAIDs and angiotensin converting enzyme inhibitors (ACEIs; HR 4.09, 95 % CI 2.02-8.27) or angiotensin receptor blockers (ARBs; HR 3.62, 95 % CI 1.80-7.31), but not with other antihypertensive drugs.

CONCLUSIONS

Exposure to NSAIDs leads to an intensification of hypertension treatment, especially in patients treated with ACEIs or ARBs. Renin-angiotensin system blockers should be avoided whenever NSAIDs are prescribed.

Cytochrome P450-mediated cardiovascular drug interactions

INTRODUCTION

There are numerous drug-drug interactions (DDIs) related to cardiovascular medications and many of these are mediated via the cytochrome P450 (CYP) system. Some of these may lead to serious adverse events and it is, therefore, essential that clinicians are aware of the important interactions that occur.

AREAS COVERED

An extensive literature search was performed to analyze the CYP-mediated cardiovascular DDIs that lead to a loss of efficacy or potential toxicity. Cardiovascular drugs may be victims or act as perpetrators of DDIs. The paper analyzes CYP-mediated drug interactions concerning anticoagulants, antiplatelet agents, antiarrhythmics, β-blockers, calcium antagonists, antihypertensive medications, lipid-lowering drugs and oral antidiabetic agents.

EXPERT OPINION

Cardiovascular DDIs involving the CYP system are numerous. Additionally, the spectrum of drugs prescribed is constantly changing, particularly with cardiovascular diseases and it is not necessarily the case that drugs that had shown safety earlier will always show safety. Clinicians are encouraged to develop their knowledge of CYP-mediated DDIs so that they can choose safe drug combination regimens, adjust drug dosages appropriately and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

A study of the pharmacokinetic interactions of the direct renin inhibitor aliskiren with allopurinol, celecoxib and cimetidine in healthy subjects

OBJECTIVE

Aliskiren is the first in a new class of orally effective direct renin inhibitors approved for the treatment of hypertension. This multiple-dose study investigated the potential for pharmacokinetic interactions between aliskiren and three drugs, each predominantly eliminated by a different clearance/metabolic pathway: allopurinol (glomerular filtration), celecoxib (cytochrome P450 metabolism) and cimetidine (P-glycoprotein and organic anion/cation transporters).

RESEARCH DESIGN AND METHODS

Three open-label, multiple-dose studies in healthy subjects investigated possible pharmacokinetic interactions between aliskiren 300 mg od and allopurinol 300 mg od (n = 20), celecoxib 200 mg bid (n = 22), or cimetidine 800 mg od (n = 22). Subjects received aliskiren alone or co-administered with allopurinol, celecoxib or cimetidine. Allopurinol and celecoxib were also administered alone and in combination with aliskiren. Plasma drug concentrations were determined by LC/MS/MS.

RESULTS

Co-administration of aliskiren with allopurinol had no effect on allopurinol AUC(tau) (ratio of geometric means 0.93 [90% CI, 0.88, 0.98]) or oxypurinol AUC(tau) (mean ratio 1.12 [90% CI, 1.08, 1.16]) and C(max) (mean ratio 1.08 [90% CI, 1.04, 1.13]), with 90% CI within the bioequivalence range 0.80-1.25, and a minor effect on allopurinol C(max) (mean ratio 0.88 [90% CI, 0.78, 1.00]). Aliskiren co-administration had no effect on AUC(tau) or C(max) of celecoxib (mean ratios and 90% CI within range 0.80-1.25). Neither allopurinol nor celecoxib significantly altered aliskiren AUC(tau) or C(max) (geometric mean ratios 0.88-1.02 with 90% CI including 1.00, but with some 90% CI outside the 0.80-1.25 range due to high variability). Co-administration of aliskiren with cimetidine increased aliskiren AUC(tau) by 20% (mean ratio 1.20 [90% CI, 1.07, 1.34]) and C(max) by 25% (mean ratio 1.25 [90% CI, 0.98, 1.59]).

CONCLUSIONS

In this multiple-dose study, aliskiren showed no clinically relevant pharmacokinetic interactions when co-administered with allopurinol, celecoxib or cimetidine in healthy subjects.

Calcium channel blockers in the spectrum of antihypertensive agents

Calcium channel blockers (CCBs) are widely used in the treatment of hypertension. Through blood pressure reduction, and possibly other mechanisms such as antioxidative effects, they may play a role in diminishing the risk for a variety of cardiovascular outcomes. The combination of CCBs with other newer antihypertensive agents such, as ACE inhibitors and angiotensin receptor blockers, may provide complementary effects on risk reduction in cardiovascular adverse events and renal disease. Although the efficacy of CCBs as antihypertensive agents has been adequately demonstrated, there have been concerns regarding the use of short acting dihydropyridines after acute myocardial infarction. There have also been questions about the role of CCBs with regards to other antihypertensive agents in renal disease. For example, differential effects of dihydropyridine and non-dihydropyridine CCBs may affect progression of renal disease and risk for diabetes. Certain precautions involving drug interactions are needed because of the effects of CCBs on the CYP450 enzyme systems.

Lack of pharmacokinetic interactions of aliskiren, a novel direct renin inhibitor for the treatment of hypertension, with the antihypertensives amlodipine, valsartan, hydrochlorothiazide (HCTZ) and ramipril in healthy volunteers

Aliskiren is a novel, orally active direct renin inhibitor that lowers blood pressure alone and in combination with existing antihypertensive agents. As aliskiren does not affect cytochrome P450 enzyme activities, is minimally metabolised, and is not extensively protein bound, the potential for drug interactions is predicted to be low. Four open-label studies investigated the pharmacokinetic interactions between aliskiren 300 mg and the antihypertensive drugs amlodipine 10 mg (n = 18), valsartan 320 mg (n = 18), hydrochlorothiazide 25 mg (HCTZ, n = 22) and ramipril 10 mg (n = 17) in healthy subjects. In each study, subjects received multiple once-daily doses of aliskiren and the test antihypertensive drug alone or in combination in two dosing periods separated by a drug-free washout period. Plasma concentrations of drugs were determined by liquid chromatography and mass spectrometry methods. At steady state, relatively small changes in exposure to aliskiren were observed when aliskiren was co-administered with amlodipine (AUC(tau) increased by 29%, p = 0.032), ramipril (C(max,ss) increased by 31%, p = 0.043), valsartan (AUC(tau) decreased by 26%, p = 0.002) and HCTZ (C(max,ss) decreased by 22%, p = 0.039). Co-administration with aliskiren resulted in small changes in exposure to ramipril (AUC(tau) increased by 22%, p = 0.002), valsartan (AUC(tau) decreased by 14%, p = 0.062) and HCTZ (AUC(tau) decreased by 10% and C(max,ss) by 26%, both p < 0.001). All other changes in pharmacokinetic parameters were also small, and not statistically significant. None of the observed pharmacokinetic changes was considered clinically relevant. Aliskiren inhibited plasma renin activity (PRA) and also prevented the reactive rise in PRA induced by valsartan. The most commonly reported adverse events were headache, dizziness and gastrointestinal symptoms (all mild in severity), which were similar in frequency during antihypertensive drug treatment alone and in combination with aliskiren except for an increase in dizziness during treatment with the combination of aliskiren and HCTZ. In conclusion, aliskiren shows no clinically relevant pharmacokinetic interactions and is generally well tolerated when administered in combination with amlodipine, valsartan, HCTZ or ramipril.

Hypertension Curriculum Review Donald G. Vidt, MD, Section Editor. Drug Interactions and Drugs That Affect Blood Pressure

Many antihypertensive drugs have important interactions with drugs used for different purposes; when these are used concomitantly, adverse effects on blood pressure can result. Fortunately, in recent years, the drug development process has generally discouraged the approval and marketing of antihypertensive drugs with this problem, although some anomalies still exist (eg, telmisartan + digoxin). Physicians who work in emergency departments are more familiar with illicit or unregulated drugs that affect blood pressure; chief among these are cocaine and other opioids, and methylphenidate and its congeners. The most important prescription drugs that affect blood pressure are the nonsteroidal anti-inflammatory drugs (including selective inhibitors of the second isoform of cyclooxygenase) and steroids. Phenylpropanolamines, some antidepressants, and sibutramine can often be avoided, as they raise blood pressure in a significant proportion of those who take them. Conversely, the hypertensive effects of calcineurin inhibitors and erythropoietin are most commonly overcome by increasing the intensity of antihypertensive drug treatment, since these drugs are essentially unavoidable in most patients who receive them.

[Antihypertensive drug-drug interactions]

A drug interaction is the quantitative or qualitative modification of the effect of a drug by the simultaneous or successive administration of a different one. Hypertensive patients, mainly the more elderly ones, frequently present concomitant diseases that require the administration of several medicines which facilitates the appearance of interactions. The lack of effectiveness of the antihypertensive treatment is a relatively frequent fact that sometimes is due to interactions of antihypertensive drugs with other treatments. It is difficult to determine the incidence of interactions, but it is related to the number of drugs administered simultaneously. Between 37 and 60% of hospital-admissions are treated with potentially dangerous drug associations and up to a 6% of fatal events are due to this circumstance. Among antihypertensive drugs, diuretics and angiotensin converting enzyme inhibitors are less affected by drug-interactions. Lipophilic beta-blockers agents may present some clinical relevant interactions, whereas calcium channel blockers, especially the non-dihydropiridinic ones, are implied in clinically relevant pharmacokinetic interactions. Among the angiotensin receptor blockers there are differences that would have to be considered when they are used in patients who receive other drugs. Although it is impossible for the doctor to remember all the clinical relevant interactions, it is important to bear in mind their existence and the possible mechanisms of production which can help to identify them and to contribute to their prevention. The most frequent interactions related with clinical problems are the pharmacokinetic ones, mainly those related to the metabolism through the cytochrome P450 system or the presystemic clearance by means of the P-glycoprotein. Enzymes of the cytochrome P450 system may present polymorphisms that can explain the individual differences in the response to drugs or the appearance of drug-interactions.