Theophylline precautions

 

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1.    Adjust dosage carefully

Theophylline has a relatively long half-life in certain patient populations (the elderly and CHF patients), consequently it may take several days to reach steady state. Dosage increases should be made with caution. The patient must be followed closely for signs of toxicity.

 

2.    Proper serum sampling is important when monitoring oral theophylline.

Suggested serum sampling times:

Rapid release: at least 2 hours post dose.
Slow release : at least 4 hours post dose.

 

3.    Factors affecting theophylline elimination

Hepatic disease

Patients with decompensated cirrhosis, acute hepatitis, and, possible, cholestasis have reduced theophylline clearance. A correlation between slow hepatic metabolism and serum albumin and bilirubin concentration has been made in patients with cirrhosis.

 

Cardiac disease

Patients with CHF have decreased theophylline clearance due to diminished blood flow to the liver. With treatment of CHF, theophylline clearance increases.

 

Fever

Acute illnesses associated with fever have been reported to prolong theophylline half-life. If fever is high and sustained, e.g., >102 for >24 hours, dosage should be reduced.

 

Diet

Ingestion of a high protein, low carbohydrate diet accelerates theophylline metabolism presumably by increasing liver enzyme activity. Dietary intake of methylxanthines, caffeine in particular, decreases theophylline metabolism by acting as a Substrate for metabolizing enzymes.

 

Cigarette smoking

Smoking of cigarettes has a profound effect on theophylline metabolism. There is a dose-related increase in theophylline clearance, with heavy smokers metabolizing theophylline twice as fast as nonsmokers.

 

Drug interactions are of major clinical importance

Cimetidine, macrolide antibiotics, and quinolones significantly decrease theophylline metabolism.  Phenytoin, phenobarbital, and rifampin significantly increase theophylline metabolism.

 

Age

Most studies report slower clearance in the elderly.

 


See also:

Introduction

Monitoring parameters

Pharmacokinetic formulas

Bibliography

 

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