Agonists:- Have both affinity and maximal intrin-sic activity. Competitive antagonists :- Have affinity but no intrinsic activity. Paial agonists:- Have affinity and submaximal intrinsic activity. Inverse agonists:- Have affinity but intrinsic activity with a minus sign (IA between 0 and -1). Ref:- kd tripathi; pg num:-41,42