Phenylbutazone 200mg/mL as an Oral Paste
Phenylbutazone is a nonsteroidal anti-inflammatory drug (NSAID) with antipyretic and analgesic activity. It binds irreversibly to the enzyme cyclooxygenase, inhibiting its activity in the biosynthesis of prostaglandins. Prostaglandins are the primary mediators of the inflammatory response causing tissue swelling and inflammation, pain, and fever. Further production of prostaglandin cannot occur until new enzyme is synthesized; resulting in a reduced concentration of prostaglandins at inflammatory sites, and reduced inflammatory responses.
Phenylbutazone is well absorbed following oral administration. The drug is distributed throughout the body, with highest levels being attained in the liver, lungs, heart, kidneys, and plasma. Phenylbutazone is up to 95% plasma protein bound. The increased vascular permeability to plasma proteins during an inflammatory process results in concentration of phenylbutazone in the inflammatory exudate.
The serum half-life of phenylbutazone is dose dependent, ranging in the horse from 3.5 hours at a dose of 2g/450kg to 6 hours at a dose of 8g/450kg. Therapeutic efficacy may last for more than 24 hours, due probably to the irreversible binding of the drug to cyclooxygenase.
Phenylbutazone is almost completely metabolised in the horse. The principal metabolites are oxyphenbutazone, with a pharmacological effect similar to phenylbutazone, and the pharmacologically inactive γ-hydroxyphenylbutazone. The first of the metabolites to be excreted is γ-hydroxyphenylbutazone which can be detected in urine up to 18 hours post administration. Oxyphenbutazone may be detected for at least 96 hours in the horse following a single oral dose.
Phenylbutazone is used for its anti-inflammatory, analgesic and antipyretic activity in the treatment of acute laminitis, bone and joint inflammation, and musculoskeletal disorders, as well as in soft tissue inflammation, tendonitis, acute tenosynovitis, capsulitis and bursitis.
Clinical response to the drug can be seen within a few hours of oral dosage, while optimum effects occur approximately 12 hours post administration.
Anti-inflammatory, analgesic and antipyretic oral paste for the relief of painful musculoskeletal conditions in horses.
DOSAGE AND ADMINISTRATION
For oral use only.
This product is contraindicated in animals with cardiac, renal or hepatic disorders, blood dyscrasias or pre-existing gastrointestinal ulceration.
Horses - Administer orally prior to feeding. 4.4 mg/kg (10 mL/450 kg) bodyweight twice daily for the first day; 2.2 mg/kg (5 mL/450 kg) bodyweight twice daily for the next four days; 2.2 mg/kg (5 mL/450 kg) once daily on alternate days or as directed by a veterinarian. Maximum daily dose should not exceed 4 grams (20 mL).
Ponies - Administer orally prior to feeding. 2.2 mg/kg (2.5 mL/225 kg) bodyweight twice daily for four days; 2.2 mg/kg (2.5 mL/225 kg) once daily on alternate days or as directed by a veterinarian. Do not exceed the recommended dose, as ponies exhibit an increased sensitivity to the toxic effects of phenylbutazone.
Phenylbutazone should not be combined with other NSAIDs or other highly protein bound drugs, such as digoxin, warfarin, and sulfonamides.
Potential adverse effects of phenylbutazone include anorexia, depression, colic, weight loss, ventral oedema, oral and gastrointestinal lesions including ulcers, and renal papillary necrosis. Ponies exhibit an increased sensitivity to the toxic effects of phenylbutazone. If any of these signs occur, discontinue treatment immediately.
If there is concern regarding development of gastric ulcers while phenylbutazone is being administered, it is safe to concurrently administer Omeprazole as Gastropell Daily oral paste to prevent ulcer formation during phenylbutazone therapy. Additionally, try to ensure that horses consume adequate rough, fibrous feeds in preference to grains and concentrates while under treatment with phenylbutazone.
MEAT WITHHOLDING PERIOD
NOT TO BE USED in horses intended for human consumption.
NEW ZEALAND INFORMATION
It is a legal requirement that this product is not used in any animal producing or intended to produce food for human consumption. Registered pursuant to the ACVM Act 1997, No. A10324. See www.nzfsa.govt.nz/acvm/ for registration conditions.
RACING/EVENT WITHHOLDING PERIOD
If used in performance animals, the regulations of the relevant authorities regarding medication should be observed.
If poisoning occurs, contact a doctor or Poisons Information Centre. Phone Australia131126 or in New Zealand 0800 764 766.
Dispose of empty container by wrapping with paper and putting in garbage.
Store below 25°C (Air conditioning). Protect from light.
ACVM A10324 (New Zealand)