Olugbenga Obasanjo, MD, MPH, PhD, CPH


October 27, 2011

In This Article

Complications Seen With Commonly Used Supplements

Table 1 lists herbal supplements commonly used in the United States, their typical uses and known toxicities, as well as drug interactions of these herbals with prescribed and over-the-counter medications. Table 1 can be used by the clinician as a handy guide to the clinical signs and symptoms of supplement toxicity, including acute and chronic effects of use as well as idiosyncratic effects and interaction with prescription drugs.

Table 1. Uses, Toxicities, and Drug Interactions of Commonly Used Dietary Supplements

Herb Common Use Known Toxicities Drug Known Drug Interactions
Echinacea Upper respiratory tract infection   Warfarin Reduced plasma levels of warfarin
Garlic Hypercholesterolemia Chopped garlic at room temperature can result in botulism Chlorpropamide Bleeding, increase in international normalized ratio (INR)
Ginkgo biloba Dementia, cognitive impairment; remedy for impotence and vertigo Gastric disturbance, headache, dizziness, and bleeding Warfarin Bleeding
Saw palmetto Benign prostatic hyperplasia      
Ginseng Physical performance Can increase blood pressure Warfarin Decrease in INR
Grape seed extract Venous insufficiency      
Green tea Cancer      
St. John's wort Depression Can increase blood pressure, causes severe headache Amitryptyline Reduced plasma concentrations of amitryptyline
Bilberry Vision impairment      
Aloe Dermatitis/wound healing (topical) Excessive amounts may cause a laxative effect    
Ma Huang (ephedra) Weight loss Hypertension and cardiovascular events    
Goldenseal Cough, upset stomach, and menstrual problems Can increase blood pressure and cause gastrointestinal distress and nervous system effects    
Feverfew Migraine Can increase blood pressure    
Kava Anxiolytic, analgesic, muscle-relaxing and anticonvulsant effects Can potentiate CNS acting substances Alprazolam Increased sedation
Prickly chaff powder Hypercholesterolemia Bone marrow toxicity, abnormal electrolyte homeostasis    
Evening primrose Premenstrual syndrome, attention-deficit/hyperactivity disorder, diabetic neuropathy Lowers seizure threshold of various anticonvulsants    
Shankhpushpi Dementia, cognitive impairment   Phenytoin May have adverse effect on blood levels of phenytoin

Data from Pharmacy Times.[6]

For more detailed information on dietary supplements and their uses, side effects, interactions, and dosing, visit WebMD's Protect Your Health: Vitamins and Supplements or Find a Dietary Supplement by Name, or check the resources section at the end of this article.

Up to 60,000 cases of ingestion of toxic levels of vitamins occur annually, primarily in children who ingest the vitamins thinking they are candy. Cases are rarely fatal. Table 2 lists the known toxicities of vitamins.

Table 2. Vitamin Toxicity

Vitamin Symptoms
A (Retinol) Blurred vision in early stages of toxicity; acute toxicity can cause headache, photophobia, anorexia, nausea, vomiting, abdominal pain, drowsiness, irritability, seizures, and skin desquamation; chronic toxicity can cause erythema, eczema, pruritus, dry and cracked skin, cheilitis, conjunctivitis, palmar and plantar peeling, alopecia, and pain and tenderness in the bones of the extremities
B1 (Thiamine) Tachycardia, hypotension, cardiac dysrhythmias, headache, anaphylaxis, vasodilation, weakness, and convulsions
B3 (Niacin) Acute toxicity can cause prostaglandin-mediated symptoms (eg, flushing, wheezing, diarrhea); chronic toxicity can cause jaundice, abnormal liver function tests, and acanthosis
B6 (Pyridoxine) Signs of sensory neuropathy (eg, paresthesias, ataxia, perioral numbness, impairment of position and vibration senses)
B2 (Riboflavin) Yellow-orange urine
B5 (Pantothenic Acid) Diarrhea
B9 (Folic Acid) Gastrointestinal disorders, sleep problems, seizures; may interfere with some chemotherapy agents
C (Ascorbic Acid) Renal colic, diarrhea, rebound scurvy in children of women taking high doses, glucose-6-phosphate dehydrogenase (G6PD)-associated hemolysis, dental decalcification, occult rectal bleeding, increased estrogen levels
D (Calciferol) Acute toxicity can cause muscle weakness, apathy, headache, anorexia, irritability, nausea, vomiting, and bone pain; chronic toxicity can cause acute symptoms and constipation, anorexia, abdominal cramps, polydipsia, polyuria, backache, hyperlipidemia, and hypercalcemia
E (Tocopherol) Acute toxicity can cause nausea, abdominal cramps, diarrhea, headache, fatigue, easy bruising and bleeding, diplopia, muscle weakness, creatinuria, and poor platelet agglutination
K (Phylloquinone) Inhibits the effect of oral anticoagulants

Data from US Preventive Services Task Force.[8]

Reporting Adverse Events

Healthcare providers and consumers can report adverse events, product use errors, and product quality problems associated with dietary supplements through an FDA voluntary online reporting system known as MedWatch. MedWatch is the FDA Safety Information and Adverse Event Reporting Program for reporting serious reactions, product quality problems, therapeutic inequivalence/failure, and product use errors with human medical products, including drugs, biologic products, medical devices, dietary supplements, infant formula, and cosmetics. If your patient has suffered a serious harmful effect or illness after taking a dietary supplement, a healthcare provider can report this by calling FDA's MedWatch hotline at 1-800-FDA-1088 or online at the Medwatch Website. The identity of the patient is kept confidential. Consumers also can report an adverse event or illness they believe to be related to the use of a dietary supplement. Health professionals and consumers also can check for dietary supplement alerts and safety information at https://www.fda.gov/Food/DietarySupplements/Alerts/default.htm or by contacting the FDA Center for Food Safety and Applied Nutrition Outreach and Information Center at 1-888-SAFEFOOD. Clinician resources can be found online or in software packages for computers and mobile devices, usually as part of an electronic health records package.


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