Corvental-D Capsules are hard gelatin capsules containing either 100 mg, 200 mg or 500 mg Theophylline Ph.Eur. in a sustained release `Divido' presentation. The capsules are coloured and sized, according to active ingredient content. Corvental-D 100 mg: blue and white (small capsule), Corvental-D 200 mg: green (small capsule), Corvental-D 500 mg: green (large capsule)

Corventa-D Capsules are used for the treatment of bronchitis and congestive heart failure in the dog. 20 mg per kg bodyweight to be administered orally once daily.

Care should be taken to ensure that dogs are weighed carefully and accurately and the dose does not exceed 20 mg/kg bodyweight.

Do not use in dogs with a known history of epileptiform seizures as convulsions have been reported in patients on theophylline treatment, often with no preceding signs of toxicity and in otherwise apparently normal animals.

Concurrent use of beta-sympathomimetics is contra-indicated, as additive or synergistic interactions resulting in exaggerated side effects may result.

Theophylline should be used with caution in patients with liver disease. When theophylline is prescribed to pregnant bitches, the risk benefit of the treatment should be assessed. Only small amounts of theophylline are excreted in milk.

The following side effects have been reported; restlessness, agitation, excitement, vomiting, diarrhoea, polydipsia, sedation, reduced appetite and polyuria.

If vomiting occurs the dose should be reduced or the treatment discontinued.

If signs of CNS excitement occur (twitching, restlessness or convulsions) discontinue treatment immediately.

Plasma theophylline levels may increase in patients under treatment with macrolide and fluoroquinolone antibiotics such as erythromycin and enrofloxacin and decrease in patients receiving phenobarbitone or phenytoin.

Theophylline may reduce the convulsive threshold in patients receiving ketamine.

Administration of theophylline shortly before halothane anaesthesia may result in arrythmogenic effects. In the case of accidental ingestion, seek medical advice immediately and show the package insert or the label to the physician.

For animal treatment only.Keep out of reach of children. Do not store above 30°C. Store in a dry place.

Dispose of used packaging in the household refuse. Unused product should be returned to the veterinary surgeon. Packs containing 60 capsules are available for all 3 strengths. The capsules are packed in blister strips.

Shelf life of the veterinary medicinal products as packaged for sale: 5 years.

Pharmacotherapeutic group: Systemic drugs for obstructive airway diseases, xanthines.

ATCvet code: QR03DA04

Theophylline is a dimethylated xanthine which was introduced into medicine in 1900. It is similar in structure to the common dietary xanthines, caffeine and theobromine, and has many pharmacological actions. It relaxes smooth muscle, relieves bronchospasm and has a stimulant effect on respiration. Theophylline dilates coronary arteries and increases the strength of contraction of the myocardium. It also acts on the kidney to induce diuresis and is a potent stimulant of the central nervous system.

Absorption: The methylxanthines are readily absorbed following oral administration. Studies in man have shown that the administration of theophylline with food may slow but not reduce absorption of the drug, and help avoid local irritation of the gastro-intestinal tract. In absence of food, theophylline solutions or uncoated tablets produce maximal plasma concentration within two hours. The rate and extent of absorption of theophylline differs between various slow release formulations and absorption of the drug appears to be slower at night. However, slow release formulations, if completed absorbed, allow loner dosing intervals with less fluctuation in serum concentration.

Distribution: Theophylline is distributed into all body compartments and human studies have shown that it crosses the placenta and diffuses into breast milk. The drug also crosses the blood brain barrier and enters the central nervous system. The apparent volume of distribution of theophylline in man ranges from 300 to 700 ml/kg and in dogs 500 to 800 ml/kg. In humans, it is about 50% bound to plasma proteins, but in dogs is lower at about 9%.

Metabolism and Excretion: Little information is available concerning the metabolism and excretion of theophylline in dogs. In man, theophylline is eliminated from the body by hepatic biotransformation into relatively inactive metabolites which are excreted in the urine. Theophylline is metabolised by demethylation and oxidation, mainly to 1,3-dimethyluric acid. Dimethyluric acid and 3-methylxanthine are also formed in smaller amounts and about 10% of the drug is excreted unchanged in the urine. The half life of theophylline in adults is 8 to 9 hours, and in children it is 3.5 hours.