Natural products and adverse drug interactions

Guided Metabolic Detoxification Program Supports Phase II Detoxification Enzymes and Antioxidant Balance in Healthy Participants

Adequate antioxidant supply is essential for maintaining metabolic homeostasis and reducing oxidative stress during detoxification. The emerging evidence suggests that certain classes of phytonutrients can help support the detoxification process by stimulating the liver to produce detoxification enzymes or acting as antioxidants that neutralize the harmful effects of free radicals. This study was designed to examine the effects of a guided 28-day metabolic detoxification program in healthy adults. The participants were randomly assigned to consume a whole food, multi-ingredient supplement (n = 14, education and intervention) or control (n = 18, education and healthy meal) daily for the duration of the trial. The whole food supplement contained 37 g/serving of a proprietary, multicomponent nutritional blend in the form of a rehydratable shake. Program readiness was ensured at baseline using a validated self-perceived wellness score and a blood metabolic panel, indicating stable emotional and physical well-being in both groups. No significant changes or adverse effects were found on physical or emotional health, cellular glutathione (GSH) and the GSH:GSSG ratio, porphyrin, and hepatic detoxification biomarkers in urine. The intervention was positively associated with a 23% increase in superoxide dismutase (p = 0.06) and a 13% increase in glutathione S-transferase (p = 0.003) activities in the blood. This resulted in a 40% increase in the total cellular antioxidant capacity (p = 0.001) and a 13% decrease in reactive oxygen species (p = 0.002) in isolated PBMCs from participants in the detoxification group. Our findings indicate that consuming a whole food nutritional intervention as a part of the guided detoxification program supported phase II detoxification, in part, by promoting enhanced free radical scavenging and maintaining redox homeostasis under the body's natural glutathione recycling capacity.

Food and Nutrition in the Pathogenesis of Liver Damage

The liver is an important organ and plays a key role in the regulation of metabolism and in the secretion, storage, and detoxification of endogenous and exogenous substances. The impact of food and nutrition on the pathophysiological mechanisms of liver injury represents a great controversy. Several environmental factors including food and micronutrients are involved in the pathogenesis of liver damage. Conversely, some xenobiotics and micronutrients have been recognized to have a protective effect in several liver diseases. This paper offers an overview of the current knowledge on the role of xenobiotics and micronutrients in liver damage.

Integration of botanicals in contemporary medicine: road blocks, checkpoints and go-ahead signals

The use of botanicals for maintaining good health and preventing diseases is undisputed. The claimed health benefits of natural health products and herbal medicines are based on traditional claims, positive results obtained in preclinical studies and early phase clinical trials that are not backed by safety and efficacy evidences approved by regulatory agencies. Although, the popularity of botanicals is growing, health care practitioners of modern medicine seldom recommend their use because of ill equipped database of their safety and potency. This review discusses problems that preclude botanicals from integrating into the mainstream contemporary therapeutics and cues that provide impetus for their realisation.

Effect of NIPRISAN® on CYP3A4 activity in vitro

NIPRISAN(®) is a phytomedicine developed from herbal products used in folkloric practice for the management of sickle cell disease (SCD). The effect of NIPRISAN(®) was tested on human cytochrome P4503A4 drug metabolising enzyme to generate clinically significant data for its safe and efficacious use. Inhibitory activity on CYP3A4 was measured with and without the addition of NIPRISAN(®), by testing different concentrations of the product at 37 °C in reactive mixtures with ketoconazole (2.5 μM) as the positive control. Results showed a low IC(50) value of 0.06 mg/ml, indicating that metabolic processes of NIPRISAN(®) are likely to inhibit CYP3A4. The result suggests possible herb-drug interaction may occur, with potential implication on common medications that are CYP3A4 substrates. It is, therefore, advocated that concomitant administration of NIPRISAN(®) along with medications that are CYP3A4 substrates should be done with caution so as not to compromise NIPRISAN(®')s established beneficial effect in the management of SCD.

In vitro inhibition of metabolism but not transport of gliclazide and repaglinide by Cree medicinal plant extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Interactions between conventional drug and traditional medicine therapies may potentially affect drug efficacy and increase the potential for adverse reactions. Cree traditional healing is holistic and patients may use medicinal plants simultaneously with the conventional drugs. However, there is limited information that these medicinal plants may interact with drugs and additional mechanistic information is required. In this study, extracts from traditionally used Cree botanicals were assessed for their potential interaction that could alter the disposition of two blood glucose lowering drugs, gliclazide (Diamicron) and repaglinide (Gluconorm) though inhibition of either metabolism or transport across cell membranes.

MATERIALS AND METHODS

The effect of 17 extracts on metabolism was examined in a human liver microsome assay by HPLC and individual cytochrome P450s 2C9, 2C19, 2C8 and 3A4 in a microplate fluorometric assay. Gliclazide, rhaponticin and its aglycone derivative, rhapontigenin were also examined in the fluorometric assay. The effect on transport was examined with 11 extracts using the intestinal epithelial Caco-2 differentiated cell monolayer model at times up to 180 min.

RESULTS

Both blood glucose lowering medications, gliclazide and repaglinide traversed the Caco-2 monolayer in a time-dependent manner that was not affected by the Cree plant extracts. Incubation of the Cree plant extracts inhibited CYP2C9, 2C19, 2C8 and 3A4-mediated metabolism, and the formation of four repaglinide metabolites: M4, m/z 451-A, m/z 451-B and the glucuronide of repaglinide in the human liver microsome assay. Gliclazide caused no significant inhibition. Likewise, rhaponticin had little effect on the enzymes causing changes of less than 10% with an exception of 17% inhibition of CYP2C19. By contrast, the aglycone rhapontigenin showed the greatest effects on all CYP-mediated metabolism. Its inhibition ranged from a mean of 58% CYP3A4 inhibition to 89% inhibition of CYP2C9. While rhaponticin and the aglycone did not show significant effects on repaglinide metabolism, they demonstrated inhibition of gliclazide metabolism. The aglycone significantly affected levels of gliclazide and its metabolites.

CONCLUSION

These studies demonstrate that the Cree plant extracts examined have the potential in vitro to cause drug interactions through effects on key metabolic enzymes.

Inhibitory effects of astaxanthin, β-cryptoxanthin, canthaxanthin, lutein, and zeaxanthin on cytochrome P450 enzyme activities

Astaxanthin, β-cryptoxanthin, canthaxanthin, lutein and zeaxanthin, the major xanthophylls, are widely used in food, medicine, and health care products. To date, no studies regarding the inhibitory effects of these xanthophylls on the nine CYPs isozymes have been reported. This study investigated the reversible and time-dependent inhibitory potentials of five xanthophylls on CYPs activities in vitro. The reversible inhibition results showed that the five compounds had only a weak inhibitory effect on the nine CYPs. Lutein did not inhibit the nine CYPs activities. Astaxanthin weakly inhibited CYP2C19, with an IC₅₀ of 16.2 μM; and β-cryptoxanthin weakly inhibited CYP2C8, with an IC₅₀ of 13.8 μM. In addition, canthaxanthin weakly inhibited CYP2C19 and CYP3A4/5, with IC₅₀ values of 10.9 and 13.9 μM, respectively. Zeaxanthin weakly inhibited CYP3A4/5, with an IC₅₀ of 15.5 μM. However, these IC₅₀ values were markedly greater than the Cmax values reported in humans. No significant IC₅₀ shift was observed in the time-dependent inhibition screening. Based on these observations, it is unlikely that these five xanthophylls from the diet or nutritional supplements alter the pharmacokinetics of drugs metabolized by CYPs. These findings provide some useful information for the safe use of these five xanthophylls in clinical practice.

Induction of expression and functional activity of P-glycoprotein efflux transporter by bioactive plant natural products

The effect of bioactive plant natural products on the expression and functional activity of P-glycoprotein (P-gp) is poorly understood. Interactions of bioactive plant-based food and dietary supplements with P-gp can cause significant alteration of pharmacokinetic properties of P-gp substrate drugs when used in combination. This can augment toxicity and/or interfere with the drug's therapeutic outcomes. This study investigated the effects of diverse commonly used plant natural products on the expression and activity of P-gp in human adenocarcinoma cells (LS-180). These natural products included the tobacco cembranoid (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (cembratriene), the palm oil-derived γ-tocotrienol, the extra-virgin olive oil-derived secoiridoid oleocanthal, and the triterpene acid asiatic acid derived from Melaleuca ericifolia and abundant in several other common plant dietary supplements. Treatment with 25μM of cembratriene, oleocanthal, γ-tocotrienol, or asiatic acid showed 2.3-3.0-fold increase in P-gp expression as demonstrated by Western blotting. These results were consistent with those obtained by quantitative analysis of fluorescent micrographs for P-gp. Accumulation studies demonstrated 31-38% decrease in rhodamine 123 intracellular levels when LS-180 cells were treated with the investigated compounds as a result of P-gp induction. Bioactive natural products can up-regulate the P-gp expression and functionality, which may induce herb/food-drug interactions when concomitantly used with P-gp substrate drugs.

Readability of patient and health care professional targeted dietary supplement leaflets used for diabetes and chronic fatigue syndrome

OBJECTIVES

The purpose of this study was to assess readability of patient and health care professional targeted dietary supplement (DS) leaflets used for diabetes mellitus (DM) and chronic fatigue syndrome (CFS) with a novel measurement tool and Flesch-Kincaid Grade Level (FKGL).

METHODS

Patient and professional leaflets for DS used to treat DM and CFS from the Natural Medicines Comprehensive Database (NMCD) and Natural Standard (NS) databases were evaluated. Leaflets were analyzed using FKGL and the author-developed health information readability analyzer (HIReA). HIReA integrates lexical, semantic, syntactic, cohesion, and style features and yields values of -1 (very hard) to 1 (very easy).

RESULTS

Patient-targeted leaflets substantially exceeded the consensus readability level (6th grade) as assessed by both FKGL (grade 13.0767) and HIReA (-0.2360). Professional leaflets were similarly more difficult to read as scored by HIReA (-0.7065) and FKGL (grade 14.7429). Most and least difficult-to-read sections in patient leaflets (NS/NMCD) were Related Terms (-0.8863)/Other Names (-0.8146), and Safety Concerns (0.0821)/Scientific Evidence (0.0629), respectively. Overall, leaflets in NS (-0.5721) were more difficult to read than those in NMCD (-0.3704). These differences appeared to be less pronounced when FKGL was used to assess the readability, indicating its lack of preciseness.

CONCLUSIONS

Readability for patient targeted DS leaflets is far more difficult than recommended levels. HIReA is a more precise method to measure readability than FKGL. The disparity between targeted levels of readability and measured levels may contribute to a lack of understanding by patients, with a resulting negative impact on adherence and outcomes.

Effects of some commonly used Saudi folk herbal medications on the metabolic activity of CYP2C9 in human liver microsomes

OBJECTIVE

To investigate the potential effects of eleven of the most commonly used Saudi folk herbal medications on the metabolic activity of CYP2C9 in human liver microsomes.

METHOD

CYP2C9-mediated 4'-hydroxylation of tolbutamide (TB) to 4'-hydroxytolbutamide (4-OH-TB) was utilized to assess the metabolic activity of CYP2C9. In the present study, an initial screening of the eleven herbs was carried out by incubating TB with microsomes and NADPH in absence or presence of a fixed concentration (25 μg/ml) of alcoholic extracts of different herbs and the metabolite formed was measured by HPLC. Herbs that showed significant effects were further investigated at a lower range of concentration.

RESULTS

Among the investigated herbal extracts, only aniseed and curcuma showed statistically significant effects on the formation of 4-OH-TB in human liver microsomes. Curcuma produced a potent inhibition on the metabolite formation and its maximum (about 45% inhibition) was observed at the highest extract concentrations (10 and 25 μg/ml). On the other hand, aniseed significantly activates the formation of 4-OH-TB and the maximum activation (about 55%) was observed at 2.5 μg/ml of aniseed extract.

CONCLUSION

The results of this study have shown that alcoholic extracts of curcuma and aniseed were capable of inhibiting and activating; respectively, the CYP2C9-mediated 4-OH-TB formation in human liver microsomes, suggesting that these herbs have the potential to interact with CYP2C9 drug substrates. None of the other nine investigated herbs was able to produce any statistically significant effect.

Grapefruit juice and verapamil: a toxic cocktail

The US public consumes grapefruit juice in large quantities, with 14% of the population drinking the juice at least weekly. Grapefruit juice is a well-documented inhibitor of the CYP3A4 isoenzyme, which is involved in the metabolism of over 50% of commonly prescribed drugs. Here we report an unusual case of verapamil toxicity in a 42-year-old female, which resulted from accidental ingestion of only three tablets of the sustained release preparation (120 mg each) over 24 hours which resulted in severe toxicity.

Clinically relevant safety issues associated with St. John's wort product labels

BACKGROUND

St. John's wort (SJW), used to treat depression, is popular in the USA, Canada, and parts of Europe. However, there are documented interactions between SJW and prescription medications including warfarin, cyclosporine, indinavir, and oral contraceptives. One source of information about these safety considerations is the product label. The aim of this study was to evaluate the clinically relevant safety information included on labeling in a nationally representative sample of SJW products from the USA.

METHODS

Eight clinically relevant safety issues were identified: drug interactions (SJW-HIV medications, SJW-immunosupressants, SJW-oral contraceptives, and SJW-warfarin), contraindications (bipolar disorder), therapeutic duplication (antidepressants), and general considerations (phototoxicity and advice to consult a healthcare professional (HCP)). A list of SJW products was identified to assess their labels. Percentages and totals were used to present findings.

RESULTS

Of the seventy-four products evaluated, no product label provided information for all 8 evaluation criteria. Three products (4.1%) provided information on 7 of the 8 criteria. Four products provided no safety information whatsoever. Percentage of products with label information was: SJW-HIV (8.1%), SJW-immunosupressants (5.4%), SJW-OCPs (8.1%), SJW-warfarin (5.4%), bipolar (1.4%), antidepressants (23.0%), phototoxicity (51.4%), and consult HCP (87.8%). Other safety-related information on labels included warnings about pregnancy (74.3%), lactation (64.9%), discontinue if adverse reaction (23.0%), and not for use in patients under 18 years old (13.5%). The average number of a priori safety issues included on a product label was 1.91 (range 0-8) for 23.9% completeness.

CONCLUSION

The vast majority of SJW products fail to adequately address clinically relevant safety issues on their labeling. A few products do provide an acceptable amount of information on clinically relevant safety issues which could enhance the quality of counseling by HCPs and health store clerks. HCPs and consumers may benefit if the FDA re-examined labeling requirements for dietary supplements.

Potentially adverse interactions between haloperidol and valerian

This study was designed to determine whether the treatment with haloperidol (HP), valerian or both in association impairs the liver or kidney functions. Valerian alone did not affect oxidative stress parameters in the liver or kidney of rats. HP alone only increased glutathione (GSH) depletion in liver, but not in kidney. However, when HP was associated with valerian, an increase in lipid peroxidation levels and dichlorofluorescein (DCFH) reactive species production was observed in the hepatic tissue. Superoxide dismutase (SOD) and Catalase (CAT) activities were not affected by the HP plus valerian treatment in the liver and kidney of rats. HP and valerian when administered independently did not affect the activity of hepatic and renal delta-aminolevulinate dehydratase (delta-ALA-D), however, these drugs administered concomitantly provoked an inhibition of hepatic delta-ALA-D activity. The delta-ALA-D reactivation index was higher in rats treated with HP plus valerian than other treated groups. These results strengthen the view that delta-ALA-D can be considered a marker for oxidative stress. Serum aspartate aminotransferase (AST) activity was not altered by any treatment. However, serum alanine aminotransferase (ALT) activity was higher in the HP group and HP plus valerian group. Our findings suggest adverse interactions between haloperidol and valerian.

Polymeric and Low Molecular Mass Efflux Pump Inhibitors for Oral Drug Delivery

Transmembrane located transporter proteins can be responsible for the low bioavailability of orally administered drugs. Drug delivery systems which can overcome this barrier caused by efflux pumps are therefore highly on demand. Within the current review, intestinal located efflux transporters, methods to identify efflux pump substrates and inhibitors as well as strategies to minimize efflux pump mediated transport of drugs are discussed. Methods include in silico screening, transport and accumulation studies and monitoring of the ATPase activity. An emphasis has been placed on efflux pump inhibitors including low molecular mass inhibitors such as cyclosporine, PSC833 or KR30031 and polymeric inhibitors such as myrj, thiomers and cremophor EL. Also formulation approaches to circumvent intestinal segments with high efflux pump expression are briefly addressed.

Dietary Fiber Intake and Endogenous Serum Hormone Levels in Naturally Postmenopausal Mexican American Women: The Multiethnic Cohort Study

This study investigated dietary fiber intake in association with serum estrogen levels in naturally postmenopausal Latina women with a wide range of fiber intake. Estrone (E1), estradiol (E2), and sex-hormone-binding globulin (SHBG) were measured in 242 women. Associations between estrogen levels and intake of dietary fiber, including insoluble and soluble fractions, quantified from a food frequency questionnaire, were examined. The biomarker enterolactone was also measured. After adjustment for age, weight, and other nondietary factors, dietary fiber intake was inversely associated with E1 and E2; there was a 22% and 17% decrease (2Ptrend=0.023 and 0.045) among subjects in the highest quintile of intake compared with the lowest. Fitting dietary fiber together with soluble and insoluble nonstarch polysaccharides (NSP) showed a much greater decrease in E1 and E2 (47% and 41%, respectively) while increased soluble NSP intake showed increases in E1 and E2 (64% and 69%, respectively). Two foods, avocado and grapefruit, showed significant positive associations with E1 (2Ptrend=0.029 and 0.015, respectively). This study suggests that different components of dietary fiber may have very significant different effects on serum estrogen levels. The suggestive findings relating increased estrogen levels to avocado and grapefruit intakes need confirmation.

Drug interaction between oral contraceptives and St. John's Wort: appropriateness of advice received from community pharmacists and health food store clerks

OBJECTIVE

To estimate the extent to which community pharmacists and health food store clerks provide appropriate advice regarding a drug interaction between oral contraceptives and St. John's wort (SJW).

DESIGN

Cross-sectional study.

SETTING

Three community pharmacy chains and three health food store chains in four highly populated counties in California.

PARTICIPANTS

Community pharmacists (n=99) and health food store clerks (n=84).

INTERVENTION

Investigators, posing as consumers, telephoned pharmacists and health food store clerks and asked the following question: "Is there a problem with taking SJW with birth control pills?"

MAIN OUTCOME MEASURES

Respondents were classified based on their ability to correctly identify the drug interaction (yes or no) and on the overall appropriateness (i.e., the absence of incorrect advice) of their advice. Comparisons were made between men and women respondents and between pharmacists and health food store clerks.

RESULTS

Community pharmacists were more likely than health food store clerks to correctly identify the drug interaction (50.5% versus 10.9%; Xchi(1 df) = 54.32, P < 0.001). Overall, 31.8% of respondents provided inappropriate advice that implied the absence of a drug interaction (26.3% of 99 pharmacists and 34.8% of 184 health food store clerks; Xchi(1 df) = 2.15, P = 0.14). Appropriateness of advice varied significantly among the three pharmacy chains (P < 0.001) and the three health food store chains (P < 0.05). Responses did not differ by gender of respondents (P = 0.18).

CONCLUSION

Lack of awareness of the potentially serious drug interaction between SJW and oral contraceptives by those who sell these products places the public at risk. Training and education, more comprehensive product labeling, and policies to refer consumers to drug information centers are needed.

Herbal product-drug interactions mediated by induction

Despite their common use, it is not widely recognized that herbal medicines can alter the efficacy of coadministered prescription drugs. Constituents in herbs interact with nuclear receptors to enhance metabolizing enzyme and/or transporter activity leading to reduced drug concentrations. Although St John's wort was the first and most frequently reported source of induction-style herb-drug interactions, this knowledge has not yet changed its current availability. This type of interaction is likely to be relevant to other herbal products. Caregivers need to be aware of the issues and options for therapeutic management.

Prevalence of natural health product use in healthy postmenopausal women

OBJECTIVES

Population studies examining dietary supplement use reveal that users are more likely to be women of older age, yet there are few focused studies among postmenopausal women. The purpose of this study was to determine the prevalence of natural health product (NHP) use, as well as the attitudes and motivations associated with NHP use, among postmenopausal women.

DESIGN

Healthy postmenopausal women were recruited from shopping malls and community centers to complete a questionnaire that collected information regarding use of NHPs; attitudes and motivations about NHPs; and demographic, health, and lifestyle characteristics.

RESULTS

The prevalence of NHP use among the 204 subjects was 83.3%. There were no significant differences in characteristics between NHP users and non-users, with the exception of a lower body mass index among NHP users (P = 0.01). The most commonly consumed NHP was calcium, followed by multivitamins/minerals, vitamin C, and vitamin E. Almost all NHP users (98.8%) believed that NHPs improved their overall health, and most (70.6%) attributed specific positive effects to their NHPs. Three quarters of NHP users believed that their NHPs could not cause adverse effects, and 64.2% believed that their NHPs could not interact negatively with medications. The most common source of NHP information was magazines/books, and 71.8% of NHP users indicated they did not need further information about their NHPs.

CONCLUSIONS

In this study, we found that the prevalence of NHP use among a sample of 204 healthy postmenopausal women was 83.3% and that, apart from body mass index, there were no variables that predicted NHP use.