TDM Theophylline Flashcards
What drug class is Theophylline?
Theophylline is a bronchodilator, belonging to the xanthine drug class
Describe the mechanism of action of Theophylline.
Theophylline relaxes the smooth muscle of the bronchial airways and pulmonary blood vessels and reduces airway responsiveness to histamine, methacholine, adenosine, and allergen. Theophylline competitively inhibits type III and type IV phosphodiesterase (PDE), the enzyme responsible for breaking down cyclic AMP in smooth muscle cells, possibly resulting in bronchodilation. Theophylline also binds to the adenosine A2B receptor and blocks adenosine mediated bronchoconstriction.
What are the adverse effects of inhibiting phosphodiesterase?
Hypertension
Tachycardia
Headache
What are the therapeutic indications of Theophylline?
Chronic asthma
Severe acute asthma
Reversible airways obstruction
What is the therapeutic range for Theophylline?
55-110 umol/L or 10-20mg/L
When should Theophylline levels be taken?
For IV Aminophylline loading dose levels should be taken: 4-8 hours post dose (peak level)
For oral Theophylline/Aminophylline: pre dose trough level and 4-8 hours post dose*
What is the ongoing level monitoring for Theophylline?
Serum levels should be monitored every 5-7 days after initiating therapy and every 3 days following dose changes
What is the half life of Theophylline?
Between 8-24 hours
Are ADR of Theophylline predictable?
Yes, adverse drug reactions to Theophylline are concentration dependent and therefore certain reactions would be expected at certain serum drug levels.
What adverse effects would you expect at Theophylline serum level of less than 5mg/L?
Nausea
What adverse effects would you expect at Theophylline serum level of between 5-20mg/L?
Insomnia
Diarrhoea
What adverse effects would you expect at Theophylline serum level of between 20-35mg/L?
Persistent vomiting
GI bleed
Seizures
Cardiac arrhythmias
What adverse effects would you expect at Theophylline serum level of greater than 35mg/L?
Arrhythmias
Convulsions
