Dr Sharon Rees @reesprescribe
Day 1: #theophylline was extracted from green and black tea leaves in 19th Century; Theophylline is a natural derivative of the purine ‘xanthine’ and structurally similar to caffeine. Used from 1902 as a diuretic and since 1930s for asthma. Oral preparation as a m.r formulation and given iv as aminophylline (more soluble).
Dr Sharon Rees @reesprescribe
Day 2: Indications for #theophylline include adult and children over 5 (UK step 3+) for chronic asthma (specialist use <5). Adults only use in severe acute asthma/COPD. Asthma 2-11yrs 9 mg/kg every 12 hrs, can increase to 10-16 mg/kg; 12-17 yrs 200-400 every 12 hrs; COPD 200-400 mg twice daily.
Dr Sharon Rees @reesprescribe
Day 3: Kinetics; #theophylline thought 100% bioavailable orally! Metabolised in liver and this process determines blood levels. Approximately 10% is renally excreted as unchanged drug. Prolonged release tablets t½ 7 hrs. Caution in hepatic impairment, heart failure andand viral infection. Can use in pregnancy.
Dr Sharon Rees @reesprescribe
Day 3 (cont); #theophylline clearance can be altered by age, weight, diet, smoking, some disease eg cardiorespiratory and hepatic. #theophylline is a drug with a narrow therapeutic index; monitor at the start and with each dose adjustment or change to clearance eg altered smoking habit.
Dr Sharon Rees @reesprescribe
Day 4: Mechanism of action is unknown for #theophylline. Thought to inhibit phosphodiesterase and antagonise adenosine, thus regulating calcium flow and impairing histamine release, leading to relaxation of bronchial smooth muscle. Also stimulates the CNS and cardiac muscle, induces diuresis and increases gastric acid secretion.
Dr Sharon Rees @reesprescribe
Day 5: The frequency of ADRs is largely unknown for #theophylline as it pre-dates licensing regs. Include arrhythmias, anxiety, nausea/vomiting, rash, abdominal discomfort, tremor, sleep disorders, convulsions. Risk of severe hypokalamia when used with beta2 agonists (not exhaustive) Prolonged release preparations can cause delayed toxicity.
Dr Sharon Rees @reesprescribe
Day 6: Drug-drug interactions for #theophylline include numerous ‘severe’ interactions from either hypokalaemia eg citalopram, clarithromycin, as well as asthma drugs eg salbutamol; OR via enzyme induction eg St John's wort, or drugs which can worsen respiratory function eg beta blockers.
Dr Sharon Rees @reesprescribe
Day 7: Interesting fact; At lower concentrations #theophylline is believed to exert an anti-inflammatory effect in lungs, reducing the number of eosinophils and IL-8. Theories include inhibition of prostaglandin levels, T cell apoptosis, antagonism TNF-alpha while increasing IL-10 (anti-inflammatory).
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Further reading on #theophylline
- Theophylline: https://bnf.nice.org.uk/drug/theophylline.html
- Uniphyllin Continus 300 mg prolonged release tablets: https://www.medicines.org.uk/emc/product/1021/smpc#gref
- Theophylline is a drug with a narrow therapeutic index TRUE or FALSE?
Renal function is more important than hepatic function when managing plasma concentration
TRUE or FALSE?
Which is TRUE?
- Smoking induces liver enzymes which increases theophylline levels
- Smoking induces liver enzymes which decreases theophylline levels
- Smoking causes lung broncho-spasm and opposes the drug effects
- Smoking reduces lung absorption of theophylline, so higher drug doses are needed
Which of the following does NOT exacerbate hypokalaemia when taken with theophylline?
- Salbutamol
- Prednisolone
- Indapamide
- Rifampicin
Theophylline has sedative effects TRUE or FALSE?
- Theophylline toxicity can manifest as
- Bradycardia and hypoglycaemia
- Tachycardia and seizure
- Rash and urinary retention
- Hypotension and renal failure
An important drug-drug interaction pathway is caused by enzyme inducers, such as carbamazepine TRUE or FALSE?
- Which best describes the action of theophylline on bronchial smooth muscle?
- Opposing adenosineactivity reduces histamine & allows more calcium availability to the smooth muscle
- Stimulates epinephrine, which opens up the airway
- Prevents constriction by lowering histamine levels
- Opposes lung damage caused by smoking
Theophylline is related to caffeine
TRUE or FALSE?
Theophylline is introduced at step 3 and above on the algorithms for chronic asthma treatment for people over 5 years old
TRUE or FALSE?