Methylcobalamin (B12) vs Pantothenic Acid (B5)

Mechanism

Methylcobalamin serves as a cofactor for methionine synthase, transferring a methyl group from 5-MTHF to homocysteine to regenerate methionine and subsequently SAMe. Adenosylcobalamin (the other active B12 form) is a cofactor for methylmalonyl-CoA mutase in mitochondrial energy production and odd-chain fatty acid metabolism. B12 is essential for myelin synthesis, DNA synthesis (thymidylate synthase pathway), red blood cell maturation, and neurological function. Deficiency causes megaloblastic anemia and irreversible subacute combined degeneration of the spinal cord.

Standard Dosing

1000-5000 mcg methylcobalamin daily (sublingual preferred)

Timing

Morning, sublingual for best absorption (bypasses intrinsic factor requirement). Can combine with methylfolate.

Cycle Duration

ongoing

Side Effects

• Acne/skin breakouts (common)
• Anxiety (overmethylation in susceptible individuals)
• Diarrhea
• Headache
• Hypokalemia (during rapid repletion of severe deficiency)

Contraindications

• Leber's hereditary optic neuropathy (cyanocobalamin specifically; methylcobalamin is generally safer)
• Polycythemia vera

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Mechanism

Pantothenic acid is converted to Coenzyme A (CoA), the universal acyl-group carrier essential for >100 metabolic reactions. CoA is required for: fatty acid synthesis and beta-oxidation, citric acid cycle (acetyl-CoA entry), steroid hormone synthesis (pregnenolone from cholesterol), acetylcholine synthesis, melatonin synthesis, and Phase II detoxification (acetylation reactions). Pantethine (the active form) supports healthy lipid metabolism by inhibiting hepatic HMG-CoA reductase and fatty acid synthase, while stimulating fatty acid oxidation.

Standard Dosing

500mg pantothenic acid or 300mg pantethine twice daily

Timing

With meals. Split doses for pantethine.

Cycle Duration

ongoing

Side Effects

• Diarrhea at high doses
• GI discomfort
• Contact dermatitis (topical dexpanthenol)

Contraindications

• Hemophilia (theoretical concern: pantethine may have mild antiplatelet effect at high doses)

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