Stephanie F. Gardner

Cytochrome P450 phenotypic ratios for predicting herb-drug interactions in humans.

Phytochemical‐mediated modulation of cytochrome P450 (CYP) activity may underlie many herb‐drug interactions. Single‐time point phenotypic metabolic ratios were used to determine whether long‐term supplementation of St Johns wort, garlic oil, Panax ginseng, and Ginkgo biloba affected CYP1A2, CYP2D6, CYP2E1, or CYP3A4 activity.

Clinical assessment of effects of botanical supplementation on cytochrome P450 phenotypes in the elderly: St John's wort, garlic oil, Panax ginseng and Ginkgo biloba.

ObjectivesElderly patients are more likely to ingest prescription medications concurrently with botanical supplements, and may therefore be vulnerable to herb-drug interactions. Phytochemical-mediated modulation of cytochrome P450 (CYP) activity may underlie many herb-drug interactions. Some evidence suggests that CYP activity may decrease in the elderly. If so, herb-mediated changes in CYP activity may take on greater clinical relevance in this population. In this study, single timepoint, phenotypic metabolic ratios were used to determine whether long-term supplementation of St John’s wort, garlic oil, Panax ginseng, and Ginkgo biloba affected CYP1A2, CYP2D6, CYP2E1 or CYP3A4 activity in elderly subjects.MethodsTwelve healthy volunteers between the ages of 60 and 76 years (mean age 67 years) were randomly assigned to receive each botanical supplement for 28 days followed by a 30-day washout period. Probe drug cocktails of midazolam, caffeine, chlorzoxazone and debrisoquine were administered before and at the end of supplementation. Pre- and post-supplementation phenotypic ratios were determined for CYP3A4, CYP1A2, CYP2E1 and CYP2D6 using 1-hydroxymidazolam/midazolam serum ratios (1-hour), paraxanthine/caffeine serum ratios (6-hour), 6-hydroxychlorzoxazone/chlorzoxazone serum ratios (2-hour) and debrisoquine urinary recovery ratios (8-hour), respectively. The content of purported ‘active’ phytochemicals was determined for each supplement.ResultsComparisons of pre- and post-St John’s wort phenotypic ratios revealed significant induction of CYP3A4 (≈140%) and CYP2E1 activity (≈28%). Garlic oil inhibited CYP2E1 activity by approximately 22%. P. ginseng inhibition of CYP2D6 was statistically significant, but the magnitude of the effect (≈7%) did not appear to be clinically relevant. None of the supplements tested in this study appeared to affect CYP1A2 activity.ConclusionsElderly subjects, like their younger counterparts, are susceptible to herb-mediated changes in CYP activity, especially those involving St John’s wort. Pharmacokinetic herb-drug interactions stemming from alterations in CYP activity may adversely affect drug efficacy and/or toxicity. When compared with earlier studies that employed young subjects, the data suggest that some age-related changes in CYP responsivity to botanical supplementation may exist. Concomitant ingestion of botanical supplements with prescription medications, therefore, should be strongly discouraged in the elderly.

In vivo assessment of botanical supplementation on human cytochrome P450 phenotypes: Citrus aurantium, Echinacea purpurea, milk thistle, and saw palmetto

Phytochemical‐mediated modulation of cytochrome P450 (CYP) activity may underlie many herb‐drug interactions. Single‐time point phenotypic metabolic ratios were used to determine whether long‐term supplementation of Citrus aurantium, Echinacea purpurea, milk thistle (Silybum marianum), or saw palmetto (Serenoa repens) extracts affected CYP1A2, CYP2D6, CYP2E1, or CYP3A4 activity.

Pharmacokinetics and cardiovascular effects of ma-huang (Ephedra sinica) in normotensive adults.

The purpose of this study was to evaluate heart rate and blood pressure responses to a commercially available source of ma‐haung, a natural source of the sympathomimetic substance, ephedrine, and to evaluate the pharmacokinetic properties of the product in normotensive, healthy adults. On day 1, twelve study participants were monitored with an ambulatory blood pressure device between hours 7 and 20. On day 2, they ingested four capsules of powdered ma‐huang at hours 8 and 17 while again wearing the monitor between hours 7 and 20. Serial plasma samples were obtained and concentrations of ephedrine were analyzed by high‐performance liquid chromatography. Pharmacokinetic parameters of ephedrine were determined from plasma concentration‐time profiles. The ephedrine alkaloid content of each capsule was also determined by high‐performance liquid chromatography. Six participants experienced a statistically significant increase in heart rate, but the effects on blood pressure were variable. The half‐life, volume of distribution, clearance, and maximum concentration in plasma of ephedrine in the ma‐huang product were similar to values previously reported for a 20‐mg, immediate‐release ephedrine tablet. Values for the absorption rate were considerably lower and time to reach maximum concentration was longer for the capsules, compared with the standard tablet. Variability in alkaloid content of ephedrine was low and yielded a mean dose of ephedrine at 19.4 mg; pseudoephedrine at 4.9 mg; and methylephedrine at 1.2 mg for a four‐capsule dose. In summary, ma‐haung had variable effects on blood pressure and increased heart rate in healthy, normotensive adults. Pharmacokinetic parameters for ephedrine were in agreement with those previously reported; however, the absorption rate was much slower after ingestion of ma‐huang.

24-Hour Ambulatory Blood Pressure Monitoring in Male Children Receiving Stimulant Therapy

OBJECTIVE: To determine whether cardiac indices are altered as assessed by 24-hour ambulatory blood pressure monitoring (ABPM) in male children receiving either chronic methylphenidate or dextroamphetamine/levoamphetamine (Adderall) therapy. METHODS: Boys 7–11 years old who were receiving methylphenidate or Adderall for a minimum of 2 months were asked to participate. Subjects wore ambulatory blood pressure monitors for 24-hour periods both off and on stimulant therapy. RESULTS: Subjects (n = 17; 8 methylphenidate, 9 Adderall) were well matched. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate differed between off and on stimulant therapy (p < 0.05). DBP load calculated from ABPM reference data was increased significantly (9.0% ± 5.6% on and 4.8% ± 4.5% off therapy; p < 0.05) while subjects were taking Adderall. There was a trend toward a greater elevation in blood pressure load during awake hours and a more pronounced decrease during the asleep hours for periods on compared with off-stimulant therapy. This trend resulted in significant (p < 0.05) nocturnal dipping on-stimulant phases compared with off-stimulant therapy for both SBP and DBP (Adderall) and SBP (methylphenidate). Two subjects (1 Adderall, 1 methylphenidate) met the criteria to be considered hypertensive based both on mean awake and 24-hour blood pressure load assessments during their on-treatment period. One additional subject receiving Adderall therapy met the criteria to be considered hypertensive based on blood pressure load criteria while off therapy only. Positive correlation coefficients (p < 0.05) were found when comparing stimulant dose (mg/kg) with the percent change of mean SBP, DBP, and heart rate between off and on therapy (r = 0.56, 0.61, and 0.58, respectively). CONCLUSIONS: These preliminary data suggest that blood pressure and heart rate appear to be altered in male patients while receiving stimulant therapy for attention-deficit hyperactivity disorder. Blood pressure and heart rate screening and monitoring during stimulant therapy to determine whether alterations become clinically significant is encouraged.

The Impact of First‐Line Antihypertensive Drugs on Erectile Dysfunction

Erectile dysfunction, a problem estimated to affect up to 30 million American men, is associated with a number of systemic illnesses and drugs. Age is not thought to be an independent risk factor for the disorder, but accompanying illnesses and their treatments may contribute to its onset. Newer classes of antihypertensive agents are less frequently associated with sexual dysfunction than diuretics or (β‐blockers. However, nearly every first‐line antihypertensive drug has been reported to cause some degree of erectile dysfunction. Management options include lifestyle modification, dosage reduction, discontinuation of the offending agent, switching to an alternative drug, and pharmacologic therapy.

New Recommendations from the 1999 American College of Cardiology/American Heart Association Acute Myocardial Infarction Guidelines

OBJECTIVE: To review literature relating to significant changes in drug therapy recommendations in the 1999 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines for treating patients with acute myocardial infarction (AMI). DATA SOURCES: 1999 ACC/AHA AMI guidelines, English-language clinical trials, reviews, and editorials researching the role of drug therapy and primary angioplasty for AMI that were referenced in the guidelines were included. Additional data published in 2000 or unpublished were also included if relevant to interpretation of the guidelines. STUDY SELECTION: The articles selected influence AMI treatment recommendations. DATA SYNTHESIS: Many clinicians and health systems use the ACC/AHA AMI guidelines to develop treatment plans for AMI patients. This review highlights important changes in AMI drug therapy recommendations by reviewing the results of recent clinical trials. Insights into evolving drug therapy strategies that may impact future guideline development are also described. CONCLUSIONS: Several changes in drug therapy recommendations were included in the 1999 AMI ACC/AHA guidelines. There is emphasis on administering fibrin-specific thrombolytics secondary to enhanced efficacy. Selection between fibrin-specific agents is unclear at this time. Low response rates to thrombolytics have been noted in the elderly, women, patients with heart failure, and those showing left bundle-branch block on the electrocardiogram. These patient groups should be targeted for improved utilization programs. The use of glycoprotein (GP) IIb/IIIa receptor inhibitors in non-ST—segment elevation MI was emphasized. Small trials combining reduced doses of thrombolytics with GP IIb/IIIa receptor inhibitors have shown promise by increasing reperfusion rates without increasing bleeding risk, but firm conclusions cannot be made until the results of larger trials are known. Primary percutaneous coronary intervention (PCI) trials suggest lower mortality rates for primary PCI when compared with thrombolysis alone. However, primary PCI, including coronary angioplasty, is only available at approximately 13% of US hospitals, making thrombolysis the preferred strategy for most patients. Clopidogrel has supplanted ticlopidine as the recommended antiplatelet agent for patients with aspirin allergy or intolerance following reports of a better safety profile. The recommended dose of unfractionated heparin is lower than previously recommended, necessitating a separate nomogram for patients with acute coronary syndromes. Routine use of warfarin, either alone or in combination with aspirin, is not supported by clinical trials; however, warfarin remains a choice for antithrombotic therapy in patients intolerant to aspirin. β -Adrenergic receptor blockers continue to be recommended, and emphasis is placed on improving rates of early administration (during hospitalization), even in patients with moderate left ventricular dysfunction. New recommendations for drug treatment of post-AMI patients with low high-density lipoprotein cholesterol and/or elevated triglycerides are included, with either niacin or gemfibrozil recommended as an option. Supplementary antioxidants are not recommended for either primary or secondary prevention of AMI, with new data demonstrating lack of efficacy for vitamin E in primary prevention. Estrogen replacement therapy or hormonal replacement therapy should not be initiated solely for prevention of cardiovascular disease, but can be continued in cardiovascular patients already taking long-term therapy for other reasons. Bupropion has been added as a new treatment option for smoking cessation. As drug therapy continues to evolve in treating AMI, more frequent updates of therapy guidelines will be necessary.

Olmesartan Medoxomil: The Seventh Angiotensin Receptor Antagonist

OBJECTIVE To review the pharmacology, pharmacokinetics, efficacy, and adverse effects of olmesartan medoxomil, an angiotensin II receptor antagonist for the treatment of hypertension. DATA SOURCES Information was obtained from MEDLINE searches (1996–April 2002) of English-language medical literature. Search terms included CS-866, olmesartan, olmesartan medoxomil, RNH-6270 (active metabolite of olmesartan), Benicar, angiotensin receptors, and antihypertensive agents. In addition, references from relevant articles were reviewed for additional citations. The authors independently reviewed literature identified in the searches. Studies evaluating olmesartan (i.e., abstracts, clinical trials, data on file with manufacturer) were considered for inclusion. STUDY SELECTION All articles identified from data sources with pertinent information regarding olmesartan medoxomil were evaluated, and all information deemed relevant was included in this review. DATA SYNTHESIS Olmesartan medoxomil is a competitively priced addition to the class of angiotensin II receptor antagonists. Monotherapy with olmesartan medoxomil in once-daily doses of 20–40 mg has produced significant reductions in systolic and diastolic blood pressure in hypertensive patients. Adverse effects have been minimal with olmesartan medoxomil, with dizziness being the only adverse effect occurring more often than with placebo in clinical trials. Additionally, animal studies indicate that olmesartan medoxomil may prove to be useful treatment for diabetic nephropathy, as well as atherosclerosis. CONCLUSIONS Olmesartan medoxomil has a favorable safety and efficacy profile, with blood pressure–lowering effects comparable to those of other angiotensin receptor blockers (i.e., losartan, valsartan, irbesartan). At this time, formulary decisions will be driven primarily by economic issues. Theoretical benefits of olmesartan medoxomil in reducing atherogenesis and lowering angiotensin II concentrations better than the alternative agents will be determined only with more extensive research. THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT ACPE UNIVERSAL PROGRAM NUMBER: 407-000-03-002-H01

Community Pharmacy Data Bases to Identify Patients at High Risk for Hypercholesterolemia

We compared the effectiveness of selectively screening pharmacy data bases to identify patients with hypercholesterolemia with that of mass cholesterol screening. Screening data bases of four community pharmacies yielded 426 patients filling prescriptions for β‐blockers, thiazide diuretics, oral hypoglycemics, insulin, sublingual nitroglycerin, nicotine gum, or nicotine patches. They were invited to attend a cholesterol screening. Eighty‐eight of the contacted patients attended, as did 97 walk‐in persons. Cholesterol readings were higher in the contacted group (p=0.017). Borderline‐high cholesterol levels (200–239 mg/dl) were reported in 36.3% of the contacted group and 29.8% of the walk‐in group. High cholesterol levels (> 239 mg/dl) were reported in 31.8% and 18.6%, respectively Targeting certain drugs that directly contribute to raising cholesterol or indicate other risk factors for coronary artery disease (e.g., diabetes mellitus) was an effective method of identifying patients with hypercholesterolemia.

Candesartan Cilexetil Effectively Reduces Blood Pressure in Hypertensive Children

Background: The angiotensin-receptor blocker candesartan cilexetil is a well-toleraled antihypertensive agent with demonstrated benefits in adults with hypertension. However, there are few data supporting its use in children with hypertension. Objective: To determine the efficacy and tolerability of candesartan cilexetil in the treatment of pediatric hypertension. Methods: In an open-label, uncontrolled pilot study, hypertensive pediatric patients were eligible tor participation if untreated systolic and/or diastolic blood pressure (BP) exceeded the 95th percentile for sex, age, and height. Patients underwent a 7-day washout period prior to initiation of weight-based dosing of candesartan cilexetil (2-8 mg daily). The dose was doubled after 7 days of therapy if inadequate antihypertensive response was determined by clinic-measured casual BP monitoring (CBPM) and home BP monitoring (HBPM). Three methods of BP measurement were compared before and after 2 weeks of treatment with the final dose of candesartan cilexetil: CBPM, HBPM, and 24-hour continuous ambulatory BP monitoring (ABPM). Self-reported adverse effects and clinical laboratory analyses were used to determine tolerability. Results: Eleven patients (mean age 14.2 y) received a final candesartan cilexetil median daily dose of 8 mg (0.13 mg/kg, range 2-16 mg). Study treatment resulted in significant reductions in systolic and diastolic BP as measured by CBPM (-7.4%, p = 0,03 and -5.9%, p = 0.01, respectively) and by ABPM (-6.0%, p = 0.03 and -10.8%, p = 0.006, respectively), but no significant reductions as measured by HBPM. No clinically significant changes in laboratory measures were observed, and patients reported nonspecific mild adverse effects. Conclusions: Candesartan cilexetil effectively reduced BP as demonstrated by CBPM and ABPM measurements and was well tolerated in this group of hypertensive children.