LD50 i.v. in mice: 720 mg/kg ^L1605.

Since the introduction of iopanoic acid (Telepaque) in 1951, widespread clinical application has demonstrated that this medium represents an ideal cholecystographic agent.1 Iopanoic acid ?-(3-amino-2, 4, 6-triiodophenyl)-?-ethylpropionic acid contains 66.68% iodine. Maximum concentration in the gallbladder occurs at from 10 to 12 hours. Iopanoic acid is excreted primarily through the intestinal tract. Its elimination is rapid and complete within 48 hours. Toxic reactions to this agent are rare, and side-effects rarely occur ^L1608.

Although the foregoing oral cholecystographic agents are relatively non-toxic substances, adverse reactions such as minor gastrointestinal disturbances or allergic reactions are occasionally observed. Therefore, it is highly desirable, in order to minimize the occurrence of these undesirable side-effects, to use as low a dose as possible and maintain the blood plasma iodine concentration at the lowest possible level without sacrificing adequate imaging of the gallbladder ^L1610.

A study was done on this agent in basic form and slow-release form ^L1610. The acute oral toxicity in mice of the basic formulation was determined, and a 7-day LD50 value of 5042 (3623-6596) mg/kg in terms of sodium tyropanoate was obtained. This compared to a Ld50 value of 3158 (1302-3900) for commercial sodium tyropanoate capsule mix (uncoated). The sustained release preparation was thus statistically significantly less toxic than the immediate-release material ^L1610.