Section 21(1)(b) in The Bihar Narcotic Drugs and Psychotropic Substances Rules, 1985
(b)A licensed chemist shall not dispense a prescription unless he is acquainted with the signature of the approved practitioner by whom it purports to have been given or is acquainted with the person or the family of the person for whose use or for the use of whose animal the prescription purports to be given and has no reason to suppose that the prescription is not genuine.