Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2023 Publisher: Ennogen Healthcare Ltd, Unit G4, Riverside Industrial Estate, Riverside Way, Dartford, DA1 5BS, UK
Pharmacotherapeutic group: Drugs for obstructive airways diseases, xanthines
ATC code: R03DA04
Theophylline is a bronchodilator. In addition it affects the function of a number of cells involved in the inflammatory processes associated with asthma and chronic obstructive airways disease. Of most importance may be enhanced suppressor T-lymphocyte activity and reduction of eosinophil and neutrophil function. These actions may contribute to an anti-inflammatory prophylactic activity in asthma and chronic obstructive airways disease.
Theophylline stimulates the myocardium and produces a diminution of venous pressure in congestive heart failure leading to marked increase in cardiac output.
Following oral administration, theophylline is efficiently absorbed and is associated with an absolute bioavailability approximating 100%. Following oral administration of UNIPHYLLIN CONTINUS tablets, the delivery of theophylline is controlled and, at steady state, peak concentrations are typically seen after approximately 5 hours.
An effective plasma concentration is considered to be 5-12 micrograms/ml, although plasma concentrations up to 20 micrograms/ml may be necessary to achieve efficacy in some cases. Do not exceed 20 micrograms/ml.
Theophylline is distributed through all body compartments; approximately 60% is bound to plasma proteins.
An effective plasma concentration is considered to be 5-12 micrograms/ml, although plasma concentrations up to 20 micrograms/ml may be necessary to achieve efficacy in some cases. Do not exceed 20 micrograms/ml.
Theophylline is metabolised in the liver to 1, 3-dimethyl uric acid and 3-methylxanthine.
Theophylline and its metabolites are excreted mainly in the urine. Approximately 10% is excreted unchanged. The mean elimination half life associated with UNIPHYLLIN CONTINUS tablets is approximately 7 hours.
The predominant factors which alter theophylline clearance are: age, body weight, diet, smoking habits, other drugs and cardiorespiratory or hepatic disease. Clearance is increased in children compared to values observed in adult subjects. Clearance decreases towards adult values in late teens.
Studies involving prolonged-release UNIPHYLLIN CONTINUS tablets have demonstrated approximately dose-proportional pharmacokinetics across the 200-600 mg dose range.
Non-clinical data reveal no special hazard for humans based on conventional studies of safety pharmacology and repeated dose toxicity.
In vitro and in vivo assays have shown both positive and negative genotoxic results for theophylline. However, oral theophylline administered daily to rats and mice for 2 years did not show carcinogenicity. Therefore, it is unlikely that theophylline poses a carcinogenic risk in humans.
Theophylline has been shown to have effects upon the male reproductive system in rodents, but at doses considered in excess of the maximum human dose indicating little relevance to clinical use.
Several embryofetal developmental studies in rats, mice and rabbits have demonstrated developmental effects independent from maternal toxicity at high doses of theophylline. Therefore, theophylline should be considered to have the potential for developmental toxicity in humans.
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