L-Carnitine, an amino acid present in weight loss supplements, may interact with some medications

One of the natural substances that is often included in weight loss products is L-Carnitine, an essential amino acid for infants but not for adults. L-Carnitine promises to transport fats stored in the body to the cells where they will be metabolized and eliminated, increasing fat burning and leading to weight loss and a decrease in LDL, blood sugar and blood pressure levels.

Various forms of oral carnitine appear in the various supplements available on the market, including L-carnitine, D-carnitine and DL-carnitine, the latter two are those associated with the majority of side effects but are frequently found in these products. Products containing them should be avoided.

Interactions of L-carnitine with valproic acid and sodium benzoate have been reported. It is likely that valproic acid, a medicine used to treat seizures, will produce toxicity if the patient being treated has a carnitine deficiency, as the medicine can result in a decrease in the levels of this substance.

It can also increase levels of warfarin, an anticoagulant medication.

Carnitine should not be used in combination with some substances such as pseudoephedrine and caffeine as they can increase the side effects of carnitine, which are nausea, vomiting, gastritis and ulcers, abdominal spasms and diarrhea.

It can also cause a decrease in blood sugar levels in people on low-carbohydrate diets and a reduction in the rate of fat metabolism, which can increase blood lipids (cholesterol and triglycerides) after stopping treatment.

Bibliography:

Coelho CdF, Mota JF, Bragrança E, Burini RC. Aplicações clínicas da suplementação de L-carnitina. Revista de Nutrição. 2005;18:651-9.