The two compounds target entirely different systems and do not compete with one another
61:104-108 Masayuki Ikeda, Makoto Asai, Takahiro Moriya, Masami Sagara, Shojiro Inou, Shigenobu Shibata, Methylcobalamin amplifies melatonin-induced circadian phase shifts by facilitation of melatonin synthesis in the rat pineal gland, Brain Research, Volume 795, Issues 12, 8 June 1998, Pages 98-104, ISSN 0006-8993, Carmen Wheatley Cobalamin in inflammation III glutathionylcobalamin and methylcobalamin/adenosylcobalamin coenzymes: the sword in the stone
Proper medical supervision is essential
Cardiovascular disease and cancer: shared risk factors and mechanisms
A common guideline for opened multi-dose vials is to date the vial when first accessed and discard within 28 days unless the manufacturer states another timeframe