Pakadali pano, pali mitundu inayi ya vitamini B12 pamsika wapadziko lonse wa API. Izi ndi hydroxycobalamin, mecobalamin, cyanobalamin ndi cobalamin adenosine. Izi ndichifukwa choti ion yapakati mu molekyulu ya B12 ili ndi magulu osiyanasiyana ogwira ntchito, motero amatchedwa mayina osiyanasiyana. Hydroxycobalamin imatchedwa hydroxycobalamin chifukwa ion yapakati ya B12 imalumikizidwa ndi gulu la hydroxyl. Pakati pa mamolekyu anayi a B12, hydroxycobalamin imakhala ndi madzi abwino kwambiri osungunuka m'madzi komanso pang'onopang'ono mumkodzo, yomwe imadziwikanso kuti cobalamin ya nthawi yayitali. Ngakhale kuchuluka kwa mayamwidwe sikungafanane ndi cyanocobalan ndi Mecobalamin, kuchuluka kwake m'maso kumakhala kokwera kwambiri, komwe kumatha kuthetsa kutopa kwamaso ndikudyetsa mitsempha yamaso. Choncho, ali ndi ena ochiritsa kwambiri amblyopia chifukwa cha poizoni. Kuphatikiza apo, hydroxycobalamin imatha kuphatikiza mwachangu ndi cyanide yaulere kupanga cyanobalamin yopanda poizoni mumadzi amadzimadzi, chifukwa chake machiritso ake ena ndi mankhwala a cyanide poisoning.