Interactions with Drugs
Vitamin A may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
Vitamin A may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be increased or decreased in the blood and may cause increased or decreased effects or potentially serious adverse reactions. Patients using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Vitamin A may cause low blood pressure. Caution is advised in people taking drugs that lower blood pressure.
Vitamin A may also interact with agents for depression, agents for diarrhea, agents for lowering cholesterol, agents for the stomach and for intestine disorders, agents for weight loss, agents for worm infections, agents that affect the nervous system, agents that affect the liver, alcohol, antibiotics, anticancer agents, antifungals, antimalarials, antivirals, birth control agents taken by mouth, folate agents, iron salts, mineral oil, nicotine, orlistat, osteoporosis agents (for decreased bone density), phytonadione (vitamin K), retinoids, skin disorder agents, thyroid agents, vaccines, and valproic acid.
Interactions with Herbs and Dietary Supplements
Vitamin A may increase the risk of bleeding when taken with herbs or supplements that increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Vitamin A may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too high or too low in the blood. It may also alter the effects that other herbs or supplements possibly have on the cytochrome P450 system.
Vitamin A may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.
Vitamin A may also interact with antibacterials, anticancer herbs and supplements, antifungals, antimalarials, antioxidants, antivirals, apple pectin, carob, carrageenan, cholesterol-lowering herbs and supplements, fat-soluble vitamins, fiber, folic acid, guar, herbs and supplements for birth control, for bone loss, for depression, for diarrhea, for obesity, for stomach and intestine disorders, and for worm infections, herbs and supplements that affect the nervous system, herbs and supplements that affect the thyroid, herbs and supplements that affect the liver, iron, microcrystalline cellulose, multiple micronutrient supplements, plant stanols and sterols, tobacco, vitamin E, vitamin K, wheat bran, and zinc.
This evidence-based monograph was prepared by The Natural Standard Research Collaboration