Controlled comparison of l-5-methyltetrahydrofolate versus folic acid for the treatment of hyperhomocysteinemia in hemodialysis patients

Background-The hyperhomocysteinemia regularly found in hemodialysis patient s is largely refractory to combined oral B-vitamin supplementation featurin g supraphysiological doses of folic acid. We evaluated whether a high-dose L-5-methyltetrahydrofolate-based regimen provided improved total homocystei ne (tHcy)-lowering efficacy in chronic hemodialysis patients. Methods and Results-We block-randomized 50 chronic, stable hemodialysis pat ients on the basis of their screening predialysis tHcy levels, sex, and dia lysis center into 2 groups of 25 subjects treated for 12 weeks with oral fo lic acid at 15 mg/d (FA group) or an equimolar amount (17 mg/d) of oral L-5 -methyltetrahydrofolate (MTHF group). All 50 subjects also received 50 mg/d of oral vitamin B-6 and 1.0 mg/d of oral vitamin B-12. The mean percent re ductions (+/-95% Cls) in predialysis tHcy were not significantly different: MTHF, 17.0% (12.0% to 22.0%); FA, 14.8% (9.6% to 20.1%); P=0.444 by matche d ANCOVA adjusted for pretreatment tHcy. Final on-treatment values (mean wi th 95% CI) were MTHF, 20.0 mu mol/L (18.8 to 21.2 mu mol/L); FA, 19.5 mu mo l/L (18.3 to 20.7 mu mol/L). Moreover, neither treatment resulted in "norma lization" of tHcy levels (ie, final on-treatment values <12 mu mol/L) among a significantly different or clinically meaningful number of patients: MTH F, 2 of 25 (8%); FA, 0 of 25 (0%); Fisher's exact test of between-groups di fference, P=0.490. Conclusions-Relative to high-dose folic acid, high-dose oral L-5-methyltetr ahydrofolate-based supplementation does not afford improved tHcy-lowering e fficacy in hemodialysis patients. The preponderance of hemodialysis patient s (ie, >90%) exhibit mild hyperhomocysteinemia refractory to treatment with either regimen. This treatment refractoriness is not related to defects in folate absorption or circulating plasma and tissue distribution.