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Clinical particulars
Target species
Horses and ponies.
Indications for use
Indicated in the treatment of musculoskeletal disorders in horses and ponies where the anti-inflammatory and analgesic properties of phenylbutazone can offer relief, for example, in lameness associated with osteoarthritic conditions, acute and chronic laminitis, bursitis and carpitis.
Contraindications
The therapeutic index of phenylbutazone is low.
Do not exceed the stated dose or duration of treatment.
Use is contraindicated in animals suffering from cardiac, hepatic or renal disease, where there is the possibility of gastrointestinal ulceration or bleeding, and where there is evidence of a blood dyscrasia or hypersensitivity to the product.
Do not administer other NSAIDs concurrently or within 24 hours of each other.
Special warnings for each target species
Discontinue treatment if no response is evident after four to five days treatment.
The clinical effect of phenylbutazone can be evident for at least three days following cessation of administration. This should be borne in mind when examining horses for soundness.
Special precautions for use in animals
Use in any animal under six weeks of age or in aged animals may involve additional risks. If such use cannot be avoided, animals may require a reduced dosage and special clinical management.
Avoid use in any dehydrated, hypovolaemic or hypotensive animal as there is a risk of increased toxicity.
It is preferable that NSAIDs which inhibit prostaglandin synthesis are not administered to animals undergoing general anaesthesia until fully recovered.
Response to long term therapy should be monitored at regular intervals by a veterinary practitioner.
Dosage should be discontinued in animals developing gastrointestinal or vascular disorders, oral ulceration or inappetance during treatment.
Special precautions to be taken by the person administering the veterinary medicinal product to animals
The product should be handled with care at all times to reduce the risk of accidental ingestion or skin contact. If accidental skin or eye contact occurs, the site should be washed immediately with water. If the product is ingested, seek medical advice immediately and show the product packaging.
Advice to doctors: gastric lavage (emesis in children) should be performed urgently. Charcoal haemoperfusion has also been shown to be beneficial. Treatment should then be administered symptomatically.
Other precautions
Some authorities (including the Jockey Club) regard phenylbutazone as a 'prohibited substance' under the rules of competition. Therefore, use of this product in a competition horse should be in accordance with the recommendations/advice of the relevant competition authorities.
Adverse reactions
Non-steroidal anti-inflammatory drugs can cause inhibition of phagocytosis and hence in the treatment of inflammatory conditions associated with bacterial infections, appropriate concurrent antimicrobial therapy should be instigated.
Use during pregnancy and lactation
The safety of phenylbutazone in pregnancy has not been established. Use during pregnancy should be avoided whenever possible, particularly during the first trimester.
Interactions
Some non-steroidal anti-inflammatory agents may be highly bound to plasma proteins and compete with other highly bound drugs to produce an increase in non-bound pharmacologically active concentrations which can lead to toxic effects.
Concurrent administration of potential nephrotoxic drugs (e.g. aminoglycoside antibiotics) should be avoided.
It is preferable that NSAIDs, which inhibit prostaglandin synthesis, are not administered to animals undergoing general anaesthesia until fully recovered.
Gastrointestinal tract ulceration may be exacerbated by corticosteroids in animals given non-steroidal anti-inflammatory drugs.
Amounts to be administered and administration route
Each marked division (2 turns of the ring) is equivalent to one unit dose (i.e. 1 g phenylbutazone).
Horses: 450 kg (1000 lb) body weight:
2 unit doses twice on day one (equivalent to 8.8 mg/kg/day), 1 unit dose twice daily for four days (i.e. 4.4 mg/kg/day) followed by 1 unit dose daily or on alternate days (i.e. 2.2 mg/kg/day), sufficient to keep the horse comfortable.
Ponies: 225 kg (500 lb) body weight:
1 unit dose (i.e. 4.4 mg/kg) on alternate days.
Remove cap from nozzle. Turn ring to required dosage. Express dose as near to the back of the tongue as possible. Replace cap after use. Store in a cool place.
Discontinue treatment if no response is evident after four to five days.
Avoid the introduction of contamination during use.
Overdose
The therapeutic index of phenylbutazone is low. In man, charcoal haemoperfusion in conjunction with dopamine has been used to treat overdosage. There is no experience of this technique in the horse.
Withdrawal periods
Not to be used in horses intended for human consumption. Treated horses may never be slaughtered for human consumption. The horse must have been declared as not intended for human consumption under national horse passport legislation.