Pro-Dynam Oral Powder Dosage and administration Pro-Dynam should be administered by mouth. For each 450 kg (1000 lb) body weight the following dosage guide should be used according to individual response: Day 1 Two sachets twice daily (equivalent to 4.4 mg/kg on each occasion). Day 2–4 One sachet twice daily (equivalent to 2.2 mg/kg on each occasion) followed by one sachet daily (2.2 mg/kg daily) or on alternate days as required. If no response is evident after 4–5 days, discontinue treatment. Hay may delay the absorption of phenylbutazone and so the onset of a clinical effect. It is advisable not to feed hay immediately prior to, or during the administration of Pro-Dynam. For ease of administration Pro-Dynam may be added to a quantity of bran or oats. The therapeutic index of phenylbutazone is low. Do not exceed the stated dose or the duration of treatment.