Folic acid supplementation dosage

Gastrointestinal adverse effects (stomatitis, anorexia, abdominal pain, dyspepsia, nausea, vomiting, diarrhea, and weight loss) are very common, particularly after oral administration of methotrexate (up to 50%), and often require dosage adjustment (3). Folic acid supplementation reduces the incidence of several gastrointestinal adverse effects. 

The lesion results from the action of a bioactivated metabolite produced by cytochrome P450. This process has most commonly been noted in patients treated for psoriasis and arthritis. The extent of damage can be reduced or controlled by increasing the dosage interval to once weekly or by routine use of folic acid supplements. Vitamin A is normally stored in liver cells, and causes significant... 

A very well documented and clinically important interaction, which has been the subject of review." Reductions in serum phenytoin levels of 16 to 50% have been described in patients taking 5 to 15 mg folic acid daily for 2 to 4 weeks. If folic acid supplements are given to folate-deficient epileptics taking phenytoin, phenobarbital, primidone and possibly pheneturide, their serum antiepileptic levels should be well monitored so that suitable dosage increases can be made. 

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