Cartiswap 1 milligram drinking solution, Cartiswap is an oral solution that contains L-carnitine, which is a nutritional supplement that has several benefits, including preventing and treating low levels of carnitine in the blood. L-carnitine is found naturally in the body, but in some medical cases, the body may find it difficult to produce it sufficiently, or the body may not be able to obtain it sufficiently from the diet, which may lead to several problems in the liver, heart, and muscles.