Doc, Where Were You During Human Physiology Class?

Folinic Acid and 5-Fluorouracil, the Cancer Drug Shortage That Isn't.

Folinic acid is routinely used in cancer chemotherapy regimens that also use 5-fluorouracil. At Medscape Today, Dr. John Marshall explains how he responds to doctors and patients who ask him how to manage a shortage of folinic acid, aka leucovorin. Although the article is titled Drug Crisis: Getting by Without Leucovorin, the article's content makes clear that there is no crisis. You can read the article by registering with Medscape, but here is a key quote.

If you really want to give leucovorin you could, in fact, just give folic acid. You could go to the drugstore, and for not very much money get some folic acid and have the patient take it throughout the duration of the leucovorin shortage.

An additional factor is that folic acid is very inexpensive compared to leucovorin. Some physicians are substituting an even more expensive brand name drug, Fusilev (levoleucovorin), that contains only the purified active form of leucovorin. The point is that the human body changes folic acid, leucovorin, and Fusilev into the same tetrahydrofolate which increases the effectiveness of the 5-fluorouracil.

Methotrexate Rescue

On the other hand, leucovorin and levoleucovorin are important to a cancer chemotherapy regimen that uses high-dose methotrexate. When there is a shortage of either, the two compounds are best used for this purpose because they save the body from the toxic effects of the high doses of methotrexate that can be an effective cancer treatment. Carefully timed doses must be given intravenously for this system to work.

Off-Label Use for Methotrexate Overdose

A common off-label use of leucovorin and levoleucovorin is to save the patient from the ill effects of a methotrexate overdose.

As reported by the American Society for Health-System Pharmacists, there is a current shortage of leucovorin, but Fusilev is available. The leucovorin shortage is yet another caused by the voluntary shutdown of the Ben Venue plant where the drug was manufactured under contract with Bedford Labs.