Reversal of tall larkspur (Delphinium barbeyi) poisoning in cattle with physostigmine.

Tall larkspur poisoning of cattle is a serious problem on western US rangelands. Single oral doses of tall larkspur ranging from 1.5 to 3 g/kg body weight were administered to steers. These doses caused clinical signs of muscular tremors and collapse. Physostigmine was administered iv, ip or sc at 0.04 to 0.08 mg/kg body weight when animals were sternally or laterally recumbent. Physostigmine given iv rapidly reversed the larkspur toxicity. Serial injections of physostigmine were generally necessary to reverse acute toxicity. Administration of physostigmine to grazing animals poisoned on larkspur was also effective. Physostigmine can be effective treatment for intoxicated cattle consuming tall larkspurs.