Low apparent volume of distribution of drug indicates that:
(A) Drug has low half life (B) Drug has low bioavailability (C) Drug has low efficacy (D) Drug is not extensively distributed to tissue
(D) Vd means "the plasma volume that would accommodate all the drug in the body, if the concentration throughout was same as in plasma". Drugs with high volume of distribution are more distributed in body and vice-versa. Low volume of distribution tells that most of the drug is retained in plasma.