(Boehringer Ingelheim) Polyflex is an injectable antibiotic used in the treatment of respiratory infections and other infections in cattle, calves, dogs and cats. Polyflex must be reconstituted with sterile water before use. The dosage of Polyflex will vary according to the severity of infection and the animal’s response. The recommended dosage of Polyflex for cattle and calves is 2-5 mg per lb body weight given IM once daily. The recommended dosage of Polyflex for dogs and cats is 3 mg per lb body weight given IM or SQ twice daily. Ampicillin.