You are hereHERBS AND THEIR INTERACTION WITH ALLOPATHIC DRUGS – A REVIEW
HERBS AND THEIR INTERACTION WITH ALLOPATHIC DRUGS – A REVIEW
Mechanism of herb drug interactions :
All the herbs interact with drugs to either cause side effects or produce additive effects, the concern rises to observe cases where herbs produces side effects as they can implicit major problems to already ill patient. Herbs interact with drug pharmacodynamically or pharmacokinetically or sometimes by both ways. Pharmacokinetic interactions result in alterations of drug or natural medicine absorption, distribution, metabolism or elimination thereby affecting drug action quantitatively. Pharmacokinetic interactions are more complicated and difficult to predict because the interacting drugs often have unrelated actions; the interactions are mainly due to alteration of absorption, distribution, metabolism, or excretion, which changes the amount and duration of a drug's availability at receptor sites. Pharmcodynamic interaction alters the way herb or drug interacts with receptor thereby producing toxic or pharmacological actions. (pharmainfo.net/reviews/herb-drug interactions).
Pharmacokinetic Interactions: These interactions take place when an herbal drug changes the absorption, distribution, metabolism, protein binding, or excretion of a drug that results in altered levels of the drug or its metabolites. Most of the pharmacokinetic drug interactions involve oxidative metabolism by the cytochrome P-450 system (CYF) or by the effect of herbal on the efflux drug transporter P-glycoprotein. The CYF system is a family of monooxygenase enzymes that are mainly found in intestinal and liver cells and catalyzes several Phase I metabolic processes, including oxidation, hydroxylation, S- and O-demethylation and oxidative deamination of more than 70% of prescription drugs.
Absorption: The term Absorption is describes the process of the physical passage of herbs or drugs from the outside to the inside. The majority of all absorption occurs in the intestines, where herbs or drugs must pass through the intestinal wall to enter the bloodstream. Several mechanisms may interfere with the absorption of drugs through the intestines. The absorption of herbs may be adversely affected if they are administered with drugs that may promote binding in the gastrointestinal tract. Herb absorption may be adversely affected in the presence of drugs that change the pH of the stomach. Drugs that affect gastrointestinal motility may also affect the absorption of herbs. Slower gastrointestinal motility means the herbs stay in the intestines for a longer period of time, thereby increasing the potential absorption. Conversely, more rapid gastrointestinal motility means the herbs stay in the intestines for a shorter time, which may decrease absorption.
[FIGURE: DOSE-EFFECT RELATIONSHIP STDY]
(Katzung G.Bertram et.al. 2009)
Distribution: Distribution refers to the process in which herbs or drugs are carried and released to different parts of the body. After absorption, herbs or drugs need to be presented to the affected area to exert their effect. Interactions occur during the distribution phase if the drug has a narrow range of safety index and is highly protein-bound. For example, Coumarin (warfarin) is an anticoagulant medication that is very highly bound to protein and has a very narrow range of safety index.
Metabolism: In most cases, drugs that stimulate greater liver metabolism do not exert an immediate effect. The metabolism rate of the liver changes slowly, over several weeks. Therefore, the effect of accelerated liver metabolism is not seen until weeks after the initiation of drug therapy. Once metabolized by the liver, most of the herbs and drugs become inactive derivatives. The rate at which the liver metabolizes a substance determines the length of time it stays active in the body. If the liver was induced to speed up its metabolic rate, herbs and drugs would be deactivated at a more rapid pace and the overall effectiveness of ingested substances would be lower. On the other hand, if the liver was made to slow down its metabolism, herbs and drugs would be deactivated at a slower pace and the overall impact of the substances would be greater.
Elimination: One more possible mechanism for producing herbal-drug interactions is modifying in renal clearance of a drug. Herbals that can inhibit tubular uptake or in other ways that can interfere with the renal clearance of a drug should be considered as having potential to produce pharmacokinetic herbal-drug interactions. The liver neutralizes incoming drugs and herbs, the kidneys are responsible for eliminating the substances and their metabolites from the body. ( Tyagi Lalit K. et.al.2010)
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