Effects of Ginkgo biloba extracts on diazepam metabolism: a pharmacokinetic study in healthy Chinese male subjects

Herb-drug interactions: A short review on central and peripheral nervous system drugs

Herbal medicines are widely perceived as natural and safe remedies. However, their concomitant use with prescribed drugs is a common practice, often undertaken without full awareness of the potential risks and frequently without medical supervision. This practice introduces a tangible risk of herb-drug interactions, which can manifest as a spectrum of consequences, ranging from acute, self-limited reactions to unpredictable and potentially lethal scenarios. This review offers a comprehensive overview of herb-drug interactions, with a specific focus on medications targeting the Central and Peripheral Nervous Systems. Our work draws upon a broad range of evidence, encompassing preclinical data, animal studies, and clinical case reports. We delve into the intricate pharmacodynamics and pharmacokinetics underpinning each interaction, elucidating the mechanisms through which these interactions occur. One pressing issue that emerges from this analysis is the need for updated guidelines and sustained pharmacovigilance efforts. The topic of herb-drug interactions often escapes the attention of both consumers and healthcare professionals. To ensure patient safety and informed decision-making, it is imperative that we address this knowledge gap and establish a framework for continued monitoring and education. In conclusion, the use of herbal remedies alongside conventional medications is a practice replete with potential hazards. This review not only underscores the real and significant risks associated with herb-drug interactions but also underscores the necessity for greater awareness, research, and vigilant oversight in this often-overlooked domain of healthcare.

Pharmacokinetic and pharmacodynamic herb-drug interactions-part I. Herbal medicines of the central nervous system

Unlike conventional drug substances, herbal medicines are composed of a complex of biologically active compounds. Therefore, the potential occurrence of herb-drug interactions is even more probable than for drug-drug interactions. Interactions can occur on both the pharmacokinetic and pharmacodynamic level. Herbal medicines may affect the resulting efficacy of the concomitantly used (synthetic) drugs, mainly on the pharmacokinetic level, by changing their absorption, distribution, metabolism, and excretion. Studies on the pharmacodynamic interactions of herbal medicines and conventional drugs are still very limited. This interaction level is related to the mechanism of action of different plant constituents. Herb-drug interactions can cause changes in drug levels and activities and lead to therapeutic failure and/or side effects (sometimes toxicities, even fatal). This review aims to provide a summary of recent information on the potential drug interactions involving commonly used herbal medicines that affect the central nervous system (Camellia, Valeriana, Ginkgo, Hypericum, Humulus, Cannabis) and conventional drugs. The survey databases were used to identify primary scientific publications, case reports, and secondary databases on interactions were used later on as well. Search keywords were based on plant names (botanical genera), officinal herbal drugs, herbal drug preparations, herbal drug extracts.

Herb-drug Interactions in Neuropsychiatric Pharmacotherapy - A Review of Clinically Relevant Findings

The management of neuropsychiatric disorders relies heavily on pharmacotherapy. The use of herbal products as complimentary medicine, often concomitantly, is common among patients taking prescription neuropsychiatric drugs. Herb-drug interaction, a clinical consequence of this practice, may jeopardize the success of pharmacotherapy in neuropsychiatry. Besides the wellknown ability of phytochemicals to inhibit and/or induce drug-metabolizing enzymes and transport proteins, several phytoconstituents are capable of exerting pharmacological effects on the central nervous system. This study reviewed the relevant literature and identified 13 commonly used herbal products - celery, echinacea, ginkgo, ginseng, hydroxycut, kava, kratom, moringa, piperine, rhodiola, St. John's wort, terminalia/commiphora ayurvedic mixture and valerian - which have shown clinically relevant interactions with prescription drugs used in the management of neuropsychiatric disorders. The consequent pharmacokinetic and pharmacodynamic interactions with orthodox medications often result in deleterious clinical consequences. This underscores the importance of caution in herb-drug co-medication.

Pharmacokinetic Interactions between Herbal Medicines and Drugs: Their Mechanisms and Clinical Relevance

The therapeutic efficacy of a drug or its unexpected unwanted side effects may depend on the concurrent use of a medicinal plant. In particular, constituents in the medicinal plant extracts may influence drug bioavailability, metabolism and half-life, leading to drug toxicity or failure to obtain a therapeutic response. This narrative review focuses on clinical studies improving knowledge on the ability of selected herbal medicines to influence the pharmacokinetics of co-administered drugs. Moreover, in vitro studies are useful to anticipate potential herbal medicine-drug interactions. In particular, they help to elucidate the cellular target (metabolic or transporter protein) and the mechanism (induction or inhibition) by which a single constituent of the herbal medicine acts. The authors highlight the difficulties in predicting herbal–drug interactions from in vitro data where high concentrations of extracts or their constituents are used and pharmacokinetics are missed. Moreover, the difficulty to compare results from human studies where different kinds of herbal extracts are used is discussed. The herbal medicines discussed are among the best sellers and they are reported in the “Herbal Medicines for Human Use” section of the European Medicinal Agency (EMA).

Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells

Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

Evaluation of risk factors, including fluconazole administration, for prolonged anesthetic recovery times in horses undergoing general anesthesia for ocular surgery: 81 cases (2006-2013)

OBJECTIVE--To determine risk factors for prolonged anesthetic recovery time in horses that underwent general anesthesia for ocular surgery. DESIGN--Retrospective cohort study. ANIMALS--81 horses that underwent general anesthesia for ocular surgery between 2006 and 2013. PROCEDURES--Descriptive information recorded included the ocular procedure performed, concurrent fluconazole treatments, analgesic and anesthetic agents administered, procedure duration, use of sedation for recovery, and recovery time. Data were analyzed for associations between recovery time and other variables. RESULTS--81 horses met inclusion criteria. In 72 horses, anesthesia was induced with ketamine and midazolam; 16 horses treated concurrently with fluconazole had significantly longer mean recovery time (109 minutes [95% confidence interval {CI}, 94 to 124 minutes]) than did 56 horses that were not treated with fluconazole (50 minutes [95% CI, 44 to 55 minutes]). In 9 horses anesthetized with a protocol that included ketamine but did not include midazolam, there was no difference between mean recovery time in horses that either received (59 minutes [95% CI, 36 to 81 minutes]; n = 5) or did not receive (42 minutes [95% CI, 16 to 68 minutes]; 4) fluconazole. Other variables identified as risk factors for prolonged recovery included duration of anesthesia and use of acepromazine for premedication. CONCLUSIONS AND CLINICAL RELEVANCE--Fluconazole administration was associated with prolonged anesthetic recovery time in horses when ketamine and midazolam were used to induce anesthesia for ocular surgery. Duration of anesthesia and premedication with acepromazine were also identified as risk factors for prolonged recovery time.

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

BACKGROUND

Omeprazole, a proton pump inhibitor (PPI), is widely used for the treatment of dyspepsia, peptic ulcer, gastroesophageal reflux disease, and functional dyspepsia. Polypharmacy is common in patients receiving omeprazole. Drug toxicity and treatment failure resulting from inappropriate combination therapy with omeprazole have been reported sporadically. Systematic review has not been available to address the pharmacokinetic drug-drug interaction (DDI) profile of omeprazole with adverse consequences, the factors determining the degree of DDI between omeprazole and comedication, and the corresponding clinical risk management.

METHODS

Literature was identified by performing a PubMed search covering the period from January 1988 to March 2013. The full text of each article was critically reviewed, and data interpretation was performed.

RESULTS

Omeprazole has actual adverse influences on the pharmacokinetics of medications such as diazepam, carbamazepine, clozapine, indinavir, nelfinavir, atazanavir, rilpivirine, methotrexate, tacrolimus, mycophenolate mofetil, clopidogrel, digoxin, itraconazole, posaconazole, and oral iron supplementation. Meanwhile, low efficacy of omeprazole treatment would be anticipated, as omeprazole elimination could be significantly induced by comedicated efavirenz and herb medicines such as St John's wort, Ginkgo biloba, and yin zhi huang. The mechanism for DDI involves induction or inhibition of cytochrome P450, inhibition of P-glycoprotein or breast cancer resistance protein-mediated drug transport, and inhibition of oral absorption by gastric acid suppression. Sometimes, DDIs of omeprazole do not exhibit a PPI class effect. Other suitable PPIs or histamine 2 antagonists may be therapeutic alternatives that can be used to avoid adverse consequences. The degree of DDIs associated with omeprazole and clinical outcomes depend on factors such as genotype status of CYP2C19 and CYP1A2, ethnicity, dose and treatment course of precipitant omeprazole, pharmaceutical formulation of object drug (eg, mycophenolate mofetil versus enteric-coated mycophenolate sodium), other concomitant medication (eg, omeprazole-indinavir versus omeprazole-indinavir-ritonavir), and administration schedule (eg, intensified dosing of mycophenolate mofetil versus standard dosing).

CONCLUSION

Despite the fact that omeprazole is one of the most widely prescribed drugs internationally, clinical professionals should enhance clinical risk management on adverse DDIs associated with omeprazole and ensure safe combination use of omeprazole by rationally prescribing alternatives, checking the appropriateness of physician orders before dispensing, and performing therapeutic drug monitoring.

Interactions between herbs and conventional drugs: overview of the clinical data

This article provides an overview of the clinical evidence of interactions between herbal and conventional medicines. Herbs involved in drug interactions--or that have been evaluated in pharmacokinetic trials--are discussed in this review. While many of the interactions reported are of limited clinical significance and many herbal products (e.g. black cohosh, saw palmetto, echinacea, hawthorn and valerian) seem to expose patients to minor risk under conventional pharmacotherapy, a few herbs, notably St. John's wort, may provoke adverse events sufficiently serious to endanger the patients' health. Healthcare professionals should remain vigilant for potential interactions between herbal medicines and prescribed drugs, especially when drugs with a narrow therapeutic index are used.

Effect of Ginkgo biloba special extract EGb 761® on human cytochrome P450 activity: a cocktail interaction study in healthy volunteers

PURPOSE

We assessed the human in vivo metabolic drug interaction profile of Ginkgo biloba extract EGb 761® with respect to the activities of major cytochrome P450 (CYP) enzymes.

METHODS

A single-center, open-label, randomized, three-fold crossover, cocktail phenotyping design was applied. In random order, the following treatments were administered to 18 healthy men and women for 8 days each: placebo twice daily, EGb 761® 120 mg twice daily, and EGb 761® 240 mg in the morning and placebo in the evening. In the morning of day 8, administration was performed together with the orally administered phenotyping cocktail (enzyme, metric): 150 mg caffeine (CYP1A2, paraxanthine/caffeine plasma ratio 6-h postdose), 125 mg tolbutamide (CYP2C9, plasma concentration 24-h postdose), 20 mg omeprazole (CYP2C19, omeprazole/5-hydroxy omeprazole plasma ratio 3-h postdose), 30 mg dextromethorphan (CYP2D6, dextromethorphan/dextrorphan plasma ratio 3-h postdose), and 2 mg of midazolam (CYP3A, plasma concentration 6-h postdose). Formally, absence of a relevant interaction was assumed if the 90% confidence intervals (CIs) for EGb 761®/placebo ratios of the metrics were within the 0.70-1.43 range.

RESULTS

EGb 761®/placebo ratios for phenotyping metrics were close to unity for all CYPs. Furthermore, respective CIs were within the specified margins for all ratios except CYP2C19 for EGb 761® 120 mg twice daily (90% CI 0.681-1.122) and for CYP2D6 for EGb 761® 240 mg once daily (90% CI 0.667-1.281). These findings were attributed to the intraindividual variability of the metrics used. All treatments were well tolerated.

CONCLUSION

EGb 761® has no relevant effect on the in vivo activity of the major CYP enzymes in humans and therefore has no relevant potential to cause respective metabolic drug-drug interactions.

Salvianolic acid B modulates the expression of drug-metabolizing enzymes in HepG2 cells

BACKGROUND

Enzymes involved in drug and xenobiotic metabolism have been considered to exist in two groups: phase I and phase II enzymes. Cytochrome P450 isoenzymes (CYPs) are the most important phase I enzymes in the metabolism of xenobiotics. The products of phase I metabolism are then acted upon by phase II enzymes, including glutathione S-transferases (GSTs). Herbs that inhibit CYPs such as CYP3A4 or that induce GSTs may have the potential to protect against chemical carcinogenesis since the mutagenic effects of carcinogens are often mediated through an excess of CYP-generated reactive intermediates. This study was designed to investigate the effects of salvianolic acid B (Sal B), a pure compound extracted from Radix Salviae Miltiorrhizae, a Chinese herb, on cell proliferation and CYP1A2 and CYP3A4 mRNA expression in the presence or absence of rifampicin, a potent inducer of CYPs and GST protein expression in HepG2 cells.

METHODS

HepG2 cells were incubated with different concentrations of Sal B. Cell proliferation was determined by SYTOX-Green nucleic acid staining. CYP3A4 and CYP1A2 mRNA expression was assayed by real-time PCR. GST protein expression was analyzed by Western blotting.

RESULTS

Low concentrations of Sal B (0-20 μmol/L) had no significant effects on cell proliferation, while higher concentrations (100-250 μmol/L) significantly inhibited proliferation in a concentration-dependent manner. Ten μmol/L Sal B, but not 1 μmol/L, down-regulated CYP3A4 and CYP1A2 mRNA expression after 24 hours of incubation, whereas both 1 and 10 μmol/L Sal B down-regulated CYP3A4 mRNA expression after 96 hours of incubation; moreover, 1 and 10 μmol/L Sal B inhibited CYP3A4 mRNA expression induced by rifampicin. Both 1 μmol/L and 10 μmol/L Sal B increased GST expression.

CONCLUSION

Sal B inhibits CYP3A4 and CYP1A2 mRNA expression and induces GST expression in HepG2 cells.