The effect of different treatment regimens in reducing fasting and postmethionine-load homocysteine concentrations.

Objectives: To determine the homocysteine-lowering effect of different treatment regimens on both fasting and postmethionine-load plasma total homocysteine (tHcy) concentrations.

Design: Descriptive study of consecutive hyperhomocysteinaemic subjects per treatment regimen. Homocysteine was measured in the fasting state and 6 h after methionine loading, both before and after 8 weeks of vitamin therapy. Hyperhomocysteinaemia was defined as a fasting tHcy and/or increase in tHcy (postmethionine-load minus fasting tHcy concentration) exceeding the 95th percentile of local controls.

Setting: Outpatient clinic of internal medicine of a large non-academic teaching hospital.

Subjects: One hundred and seventeen hyperhomocysteinaemic subjects (vascular patients and first-degree relatives).

Interventions: There were four regimens: pyridoxine, 200 mg; folic acid, 5 mg; combination of folic acid 0.5 mg and pyridoxine 100 mg; and folic acid, 0.5 mg daily.

Results: All regimens, except pyridoxine 200 mg, significantly reduced fasting tHcy without differences in the percentage reduction (32-38%). All regimens produced a significant reduction in the increase in tHcy and postmethionine-load tHcy. The reduction in postmethionine-load tHcy was smaller for pyridoxine 200 mg than for combination therapy. No differences were found in the percentage reduction (for both increase in tHcy and postmethionine-load tHcy) between folic acid 5 mg and folic acid 0.5 mg.

Conclusions: Monotherapy folic acid (0.5 mg daily) is the lowest effective therapy for reducing both fasting and postmethionine-load tHcy concentrations, with the same results as high-dose folic acid (5 mg daily). Pyridoxine has no additional value.