Rather than pale and small RBC’s (hypochromic microcytic) which you’d find in iron deficiency anemia, the red blood cells look huge in megaloblastic anemia. The two main causes of megaloblastic anemia are either a folic acid deficiency or a B12 deficiency.
Folic Acid Deficiency Onset of Symptoms: 2 months (faster than B12 deficiency of a year)
Etiology (Reasons for Folic Acid Deficiency): Poor diet, especially alcoholics as they don’t eat well or get their vitamins.
The State of California was thinking of passing a law, to protect the alcoholics, that would require beer and wine makers to add B vitamins and folic acid in their beer and wine. Funny way to take care of a problem. The law never passed.
Drug Interactions
- Phenytoin (Dilantin) blocks absorption of FA so we give them more folic acid to override this.
- Birth Control pills also block the absorption of folic acid. Some birth control pills have iron and folic acid in the placebo (7 day) pills for this purpose.
- Methotrexate, used as a chemotherapy drug in high doses (sometimes with RA doses), blocks absorption of folic acid.
- Co-trimoxazole, in high doses, can also cause a folic acid deficiency.
Folic acid is not the active vitamin. Our body has to convert folic acid to the active vitamin. Our body takes two enzymatic steps to convert it into the active vitamin, called tetrahydrafolate, also known as folinic acid.
Methotrexate in high doses, kills cancer cells because it doesn’t allow folic acid to be converted to tetrahydrofolate (folinic acid).
Co-trimoxazole in low doses is not a problem, it doesn’t affect our normal cells but it kills our bacteria for the same reason (bacteria can’t convert folic acid to the active form and they die). In high doses, when we’re treating HIV patients, we’re using high doses of this antibiotic and patients may develop folic acid deficiency.
When we treat cancer patients with these drugs to kill cancer cells, we also affect our normal cells and they end up becoming anemic. The treatment is to give them folinic acid because the chemotherapy drug doesn’t allow the converting of folic acid to folinic acid. Leucovorin (Welcovorin) is this folinic acid. If a person doesn’t have a problem converting folic acid, we don’t give people folinic acid because it’s very expensive.
In order to kill a cancer cell, you have to enter it. Cancer cells grow faster than normal cells do and because they’re going to use this folic acid faster than normal cells, we’re going to kill off cancer cells before the normal cells. Before we kill off too many normal cells, we have to rescue the normal cells. We give them the Leucovorin (Welcovorin) after they have been given their methotrexate dose. But what also happens is that their cancer cells recover as well. We will go into greater detail about this later in specific oncology posts.
Therapy for folic acid deficiency.
- The therapy is to give them folic acid to overcome the decreased absorption.
- However if they are on Methotrexate or Co-trimoxazole, we give them tetrahydrofolate/folinic acid, called Leocovorin (Welcovorin).
