Theophylline

Methylxanthines

Mechanism :

blocks actions of phosphodiesterase and
adenosine  / increases cAMP levels due to decreased cAMP hydrolysis

Effects:

bronchodilator, antinflammatory, bronchoprotective

positive cardiac inotropic effects, produces vasodilation, has diuretic action and stimulates diaphragmatic contraction

Use :

for maintenance therapy in patient with moderate to severe asthma / usage is limited because of narrow therapeutic index (cardiotoxicity, neurotoxicity)

Side Effects :

capable of causing nausea, insomnia

Acute toxicity :

vomitin, abdominal pain, seizures and cardiac arrhythmias
seizures most common cause of morbidity and mortality, followed by tachyarrhythmia but does not cause QT-prolongation

• beta-blocker are drug of choice for theophylline induced tachyarrhythmias
• seizures are difficult to treat but use benzo and barbiturates

Clearance :

metabolized by cytochrome P450

varies with age (highest in young adolescents) ; half life in children is less because of faster hepatic metabolism

smoking status (higher in smokers)

concurrent use of other drugs that inhibit or induce hepatic enzymes