Herbal Remedies: Drug-Herb Interactions 笔记 part 1
Content:
2. STANDARDIZATION AND QUALITY CONTROL
3. DRUG INTERACTIONS
4. DRUG-HERB INTERACTIONS
5. SELECTED POPULAR HERBS
i. Ginkgo (Ginkgo biloba)-----------------------------(Part 1)
1. Herbs harmless?
About one third of our drugs, including
- digitalis洋地黄
- medicine that is used to treat certain heart conditions
- morphine嗎啡
- treat severe pain
- atropine
- treat the symptoms of low heart rate
- several chemotherapeutic agents
- were developed from plants.
Herbs can affect body functions; therefore, when herbs are taken concurrently with drugs, interactions are possible.
2. STANDARDIZATION AND QUALITY CONTROL
Because herbs are sold as food supplements, companies are not required to prove the efficacy of the herbs or determine the side effects or interactions of these products.
Often, multiple ingredients are present in the same bottle, and products are sometimes mislabeled, misidentified, and adulterated.
The potency of herbs can also vary depending on the climate and soil conditions where they were grown.
When a drug is prescribed, the dosage and quality of the product is more or less assured; such is not the case with herbs.
Even with these drawbacks, herbs are an effective form of therapy.
3. DRUG INTERACTIONS
Drug interaction
- any modification caused by another exogenous chemical (drug, herb, or food) in the diagnostic, therapeutic, or other action of a drug in or on the body.
The possibilities of drug interaction are endless, because
- more than 30000 over-the-counter products
- more than 1000 unique chemical substances from which prescription drugs are produced
- hundreds of herbs, vitamins, and minerals are available.
The risk for drug interactions
- increases with the number of products consumed
- for 2 products, the risk is 6%
- for 5 products, 50%
- for 8 or more products, 100%.
The mechanisms for drug interaction
- divided into
- pharmacokinetics
- absorption
- distribution
- metabolism
- excretion
- pharmacodynamic interactions
- the combined pharmacological effects of a drug
Related link: 【Pharmacology】 Pharmacokinetics 【Pharmacology】Pharmacodynamics
4. DRUG-HERB INTERACTIONS
Pharmacokinetic Interactions
i. Absorption
- Herbs have hydrocolloidal carbohydrate components, such as gums and mucilage
- soluble in water
- poorly absorbable
- example:
- psyllium 车前子
- rhubarb 大黄
- flaxseed 亚麻籽
- marshmallow 药蜀葵
- 性味：甘，溫
- 功效：解表散寒，利尿，止咳，消炎解毒
- 治疗：疮疖痈肿，突发、气管炎，风寒实例
- 内服：煎汤，6-9克。
- aloe
 |
| Marshmallow |
These compounds are apt to bind to other drugs, particularly when consumed in their whole or powdered forms.
a. Psyllium
- an herb high in mucilage富含粘液
- inhibits the absorption of lithium.
Lithium Review: 【Pharmacology】Antidepressants
b. Rhubarb & aloe
- cause diarrhea, which reduces the action of drugs that have a narrow therapeutic index (eg, digoxin, warfarin).
Digoxin Review: 【Pharmacology】Antiarrhythmic 【Pharmacology】Drug for Heart Failure
In order to prevent an herb from binding with drugs, the drug should be taken 1 hour before or 2 hours after these herbal products.
ii. Distribution
Herbs such as meadowsweet and black willow, which contain pain-reducing salicylates,
- may displace highly protein-bound drugs such as
- warfarin
- carbamazepine (Tegretol)
- increasing the adverse effects of the drugs.
- These products should not be taken concurrently. 不可同时服用
iii. Metabolism
Licorice
- as an herb, not a sweetener
- decreases the metabolism of corticosteroids
- leading to adverse and toxic effects from the buildup of corticosteroids.
St John’s wort can induce hepatic microsomal enzymes in the cytochrome P-450 system
- thus, it increases the metabolism of drugs metabolized in this system, such as
- digoxin and theophylline,
- protease inhibitors,
- and cyclosporine.
- The drugs are thus rendered less effective, so concurrent use of licorice with these drugs is not recommended.
Pharmacodynamic Interactions
An example of a pharmacodynamic interaction is additive activity.
For example,
i. Benzodiazepines & valerian
- the hypnotic activity of benzodiazepines is increased by valerian缬草
- valerian缬草: 治心神不安，胃弱，腰痛，月经不调，跌打损伤
ii. warfarin &ginkgo
- the anticoagulant action of warfarin is enhanced by ginkgo and possibly by many other herbs
It is best not to take these products concurrently.
Benzodiazepines Review: 【Pharmacology】Anxiolytic and hypnotic drugs 【Pharmacology】Antiepileptic drugs
5. SELECTED POPULAR HERBS
i. Ginkgo (Ginkgo biloba)
- improve cognitive function in persons with
- Alzheimer’s disease
- dementia
- improve blood flow in persons with
- peripheral vascular disease
- tinnitus
- memory impairment
Patients who experienced bleeding were from 33 to 78 years old;
- one person was taking no other drugs concurrently, whereas several other patients were taking aspirin, warfarin, acetaminophen, or an ergotamine-caffeine preparation concurrently.
- Patients had both minor and major episodes of bleeding, and one person died of a massive cerebral hemorrhage
Patients taking other products known to affect platelet activity, such as
- vitamin E (>1200 IU)
- excessive garlic (the equivalent of 15 to 20 cloves/day)
- warfarin
- aspirin
- low molecular weight heparins
should be cautioned about the potential interaction of those products with ginkgo.
Patients taking ginkgo should be counseled to inform their healthcare providers of
- unusual bleeding and bruising
- new onset of
- dizziness
- headache
- blurred vision
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