Herb-Drug Interactions

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Herb-Drug Interactions:
The use of herbs as a complementary and alternative medicine has increased steadily over the last decade. The WHO (2002) report stated that more than 80% of the world market depending on herbal medicinal products. In Asian countries, approximately 80% population use herbal medicine for promoting health conditions and healing several diseases (Young et al., 2011).
In India and China, traditionally herbs are widely used in Ayurveda and Traditional Chinese medicines (TCM) systems, respectively. Ayurveda (Ayur, life; Veda, science or knowledge) is an ancient medical science of India. It is included several herbs viz., aloe-vera, garlic, ginger, brahmi, ashoka, neem and tulsi. In Traditional Chinese medicines (TCM), several
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Whereas, simultaneous administration with aspirin, acetaminophen, trazodone, ibuprofen and warfarin, it is reported to inhibit platelet aggregation activity resulting in spontaneous bleeding (Gohil et. al., 2007). Several herbs as kava-kava, ginger, echinacea, ginseng and garlic shows significant herb-drug interaction (Izzo et. al., 2004).
CYPs mediated herb-drug interactions:
Herb-drug interactions involving the CYP isoforms generally result in enzyme induction or inhibition. As shown in figure 2, Co-administration of herbs (CYPs inhibitor activity) with narrow therapeutic index drugs may results in enhanced plasma drug concentrations leading to toxicity. Long term consumption of herbs may induce CYPs enzymes by enhancing the rate of enzyme synthesis. Due to the increased amount of CYPs, rate of metabolite production is increase; whereas serum Half-life and drug response decreases. This lead to sub-therapeutic drug response, finally results into therapy
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It is long process; few days are required for synthesis of new enzymes. In human, CYPs isoforms like CYP1A1, 1A2, 2B6, 2C8, 2C9, 2C19 and 3A4 are induced by drug, whereas CYP2D6 is not inducible. It is reversible process; generally occurs through two mechanisms as given: i) increasing gene transcription and ii) stabilizing the mRNA or enzyme (e.g., CYP2E1). For the induction of CYP3A and 2B isoforms, gene transcriptional activation is mediated by nuclear receptors viz., pregnane X receptor (PXR), constitutive androstane receptor (CAR), G protein-coupled receptor and vitamin D3 receptor. Whereas, induction of CYP1A enzyme mediated by aryl hydrocarbon receptor (AhR). Depending on the case, CYP450 induction may be beneficial or harmful. For example, the induction of CYP1 isoforms by β-naphthoflavone reduces the carcinogenicity of 7, 12-dimethylbenz-α-anthracene in rodents. In contrast, CYP1A isoforms can also activate compounds such as benzo-α-pyrene to their carcinogenic metabolite, and the induction of these isoforms increases the risk of carcinogenicity (Martignoni et. al., 2006). St. John's wort is CYP 3A4, 2C9 and 1A2 inducer, affects the pharmacokinetic of several drugs such as cyclosporine, theophyllin, warfarin, oral contraceptives, digoxin, indinavir and

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