Selective actions of aspirin- and sulphasalazine-like drugs against prostaglandin synthesis and breakdown.

Groups of ten aspirin- and five sulphasalazine-like drugs were tested as inhibitors of prostaglandin synthesis (rabbit renal medulla 14,000 g supernatants) and prostaglandin breakdown (rabbit colon 100,000 g supernatants). The aspirin-like drugs exhibited selectivity against synthesis but all also inhibited breakdown at higher doses. The sulphasalazine-like drugs (including diphloretin phosphate and carbenoxolone) exhibited selectivity against breakdown and some, but not all, inhibited synthesis at higher doses. It is proposed that there are accordingly two pharmacologically distinct groups of drugs, and that they can be characterised by the ratios of ID50S against breakdown and synthesis (M/S ratio).