Common Supplement-Drug Interactions
Vitamins, minerals and herbal supplements are increasingly being taken all over the world and providing significant benefits. However, it is crucial to know that your supplements can interact with certain medications and even other supplements.
It's a must to pay attention to the way each supplement can affect your medications, so that you can use them properly. Below are some common supplement interactions, for your general knowledge.
Turmeric supplements are generally used for a variety of health issues, such as osteoarthritis, abdominal pain, rheumatoid arthritis, dyspepsia and Crohn's disease.
Anticoagulant drugs & Anti-platelet drugs
Both anti-coagulant and anti-platelet drugs are indicated to decrease platelet aggregation and to prevent blood clots. The administration of supplements containing turmeric was shown to increase the effects of the previous drugs, which in turn can result in a high tendency of bleeding. [1, 2]
Examples of those drugs include: aspirin, warfarin (Coumadin), clopidogrel (Plavix), ticlopidine (Ticlid), dalteparin (Fragmin), enoxaparin (Lovenox) and heparin.
A lot of people are struggling with diabetes, taking medications to lower the levels of glucose in blood. It was shown that curcumin, which is the main active ingredient of Turmeric, can also lower both glucose and another substance known as glycosylated hemoglobin.
Thus, if you're a diabetic, please, take care, as Turmeric may make you prone to hypoglycemia. [3, 4]
Examples of anti-diabetic medication include: insulin, glimepiride (Amaryl), tolbutamide (Orinase), pioglitazone (Actos), chlorpropamide (Diabinese), and glipizide (Glucotrol).
Drugs metabolized by cytochrome CYP3A4
After the administration of any drug, that drug should be eliminated to outside the system. That process is known as metabolism. Turmeric administration is likely to inhibit the cytochrome CYP3A4. That in turn can cause the drugs that are eliminated by this cytochrome to accumulate in your body, making you at a high risk of toxicity. 
Examples of those drugs:
- some calcium channel blockers (diltiazem, nicardipine, verapamil)
- chemotherapeutic agents (etoposide, paclitaxel)
- antifungals (ketoconazole, itraconazole)
- alfentanil (Alfenta)
- cisapride (Propulsid)
- fentanyl (Sublimaze)
- lidocaine (Xylocaine)
People taking estrogen replacement therapy are likely not to benefit from this treatment, in case they are concomitantly taking turmeric supplements. The reason is that curcumin competes with estrogen at the same receptors that estrogen needs to bind to so as affect the body. 
Black pepper is also generally used for arthritis, depression, asthma, stomach upset, bronchitis and cholera.
Antiplatelet drugs/ anti-coagulants
Black pepper contains an ingredient known as piperine, which was noted to decrease platelets aggregation. Thus, if you concomitantly take black pepper with antiplatelet or anti-coagulant drugs, you'd be at a high risk of bleeding. 
Piperine also decreases the level of glucose in blood, making people taking anti-diabetic drugs at a high risk of hypoglycemia, in case of concomitantly taking anti-diabetic drugs. 
Patients taking the anti-epileptic drug carbamazepine should be cautious, if they are willing to take black pepper, as piperine increases blood flow to the gastrointestinal tract, improving the absorption rate of carbamazepine, which in turn can result in carbamazepine toxicity. 
Drugs metabolized by cytochrome CYP2D6
Black pepper can inhibit the activity of a certain cytochrome known as CYP2D6, resulting in increasing the side effects of the drugs metabolized by those drugs, which include, for example, amitriptyline (Elavil), codeine, paroxetine (Paxil), desipramine (Norpramin), haloperidol (Haldol), imipramine (Tofranil), ondansetron (Zofran), tramadol (Ultra) and venlafaxine (Effexor). 
Vitamin D3 & K2
Both vitamin D3 and vitamin K2 are essentially required for vital processes in the body. While Vitamin D3 is used to prevent vitamin D deficiency, and other issues, such as osteoporosis, muscle weakness, autoimmune disease, and rheumatoid arthritis; on the other side, vitamin K supplements are used to prevent blood coagulation and hypoprothrombinemia.
Some people, especially those with renal failure are much prone to aluminum toxicity, in case of taking vitamin D3-containing supplements concomitantly with aluminum-containing drugs, as vitamin D improves the absorption of aluminum from intestine. For example, Alternagel. [11, 12]
Vitamin D administration improves the activity of the enzyme responsible for metabolism of the common anti-cholesterol drug atorvastatin. Therefore, if you're taking vitamin D supplements with atorvastatin, the latter levels will be decreased, and so will its effectiveness. 
People with heart-related issues, who take drugs containing digoxin, such as Lanoxin are much prone to fatal cardiac arrhythmia, if they take vitamin D supplements at the same time. The reason is that vitamin D increases the levels of calcium in blood. 
People taking vitamin K supplements along with anti-diabetic drugs are prone to hypoglycemia (decreased glucose levels in blood), as a result of the improving effects of vitamin K on the sensitivity of insulin, as well as decreasing postprandial levels of glucose. 
Warfarin is an anti-coagulant drug whose effects are significantly affected by vitamin K levels in the body. If you take much vitamin K supplements; while you're on Warfarin or other anti-coagulants, it may diminish the effects, which can be dangerous. 
5-HTP is a substance resulting from the amino acid L-tryptophan. 5-HTP-containing supplements are used to relive and prevent insomnia, anxiety, depression and migraine.
It is strongly advised to avoid taking 5-HTP supplements at the same time with anti-depressants, as 5-HTP can stimulate the effects of anti-depressants, resulting in a risky syndrome known as serotonin syndrome, in addition to cerebral vasoconstrictive disorders. 
- Fuoxetine (Prozac), o paroxetine (Paxil) o sertraline (Zoloft)
- clomipramine (Anafranil) o imipramine (Tofranil)
Carbidopa is a drug used to treat Parkinson's disease. Taking 5-HTP along with Carbidopa can result in a case that makes your skin inflamed, thickened and hard. That case is known as a scleroderma-like illness. 
Garlic is also a herb used for the treatment and prevention of some issues, such as hypertension, hyperlipidemia, hypotension, and familial hypercholesterolemia.
The same as black pepper, garlic
Anti-coagulant drugs/anti-platelet drugs
administration concomitantly with anti-coagulant drugs can make you prone to bleeding 
Taking garlic with anti-hypertensive drugs can make you prone to severe hypotension. Examples of those drugs: Nifedipine (Adalat, Procardia)
- Verapamil (Calan, Isoptin, Verelan) o Diltiazem (Cardizem)
- Isradipine (DynaCirc) o Felodipine (Plendil) o Amlodipine (Norvasc)
Both ginkgo and ginseng are herbs used to enhance cognitive function and memory, reduce fatigue, and to improve both physical and mental performance.
Ginkgo administration can decrease the effectiveness of Alprazolam .
Ginkgo seeds contain an ingredient known as ginkgotoxin, which can cause seizures. Therefore, if you're taking ginkgo; while you're on anticonvulsant drugs, the effectiveness of anticonvulsant drugs is prone to be lowered. 
- Phenobarbital, primidone (Mysoline( o Valproic acid (Depakene)
- Gabapentin (Neurontin) o Carbamazepine (Tegretol) o Phenytoin (Dilantin)
Anti-coagulant drugs/anti-platelet drugs
Both anti-coagulant drugs and a main active ingredient of ginseng, which is known as Ginsenoids, decrease platelets aggregation, resulting in increasing the risk of bleeding. 
Taking ginseng supplement; while you are on anti-diabetic drugs makes as you at a risk of hypoglycemia (decreased glucose levels in blood) .
Zinc is an element essentially required for your body, which means that you daily need to get zinc either from foods or from supplements, as it can't be synthesized in the body. Zinc supplements are used for many issues, such as those related to wound healing, immunity, reproduction, vision, growth, smell, and blood clotting.
The same as ginseng, if zinc supplements are taken along with anti-diabetic drugs, hypoglycemia is much likely to occur. 
Taking amiloride drug with zinc supplements can result in zinc toxicity, as amiloride decreases the urinary excretion rate of zinc, causing the body to store zinc for longer time through 
Therefore, if you're planning to take any of the previously mentioned supplements; while you are on any medications, please, pay attention to the way those supplements can interfere with your medications. Considering a time interval between your supplements and medications can help you avoid a lot of the side effects that are likely to occur. However, a medical advice from your doctor is still required.
The information provided on this site is intended for your general knowledge only and is not a substitute for professional medical advice or treatment. The list of interactions is not exhaustive. Always consult your doctor before taking supplements, especially, if you're taking medications or if you have a family history of certain conditions, such as blood clots/heart disease etc.
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