Menadione, a phased-out synthetic form of Vitamin K, is also known to be toxic. Menadione is a synthetic provitamin of vitamin K. These doses have yielded no reported cases of toxicity from menadione in livestock or pets. Menadione is an organic compound with the formula CH(CO)CH(CH). Low-dose menadione is still used as an inexpensive micronutrient for livestock in many countries. Menadione in combination with vitamin C has been investigated for the treatment for prostate cancer.