Can i give my dog penicillin for parvo? Administer twice weekly for up to 4 weeks (maximum of 8 injections) at approved dosage of 2 mg/lb body weight (0.02 ml/lb or 1 ml/50 lb) by intramuscular (im) injection only. In dogs and cats, the typical dose of penicillin g ranges from 10,000 to 25,000 units per pound (20,000 to 50,000 units/kg) two to six times a.