Examples
Theophylline
Aminophylline
Narrow TI
How do the Xanthines work?
- Phosphodiesterase inhibitor
- They inhibit leukotriene synthesis and therefore cause bronchodilation and inflammation
What is the difference between Theophylline and Aminophylline?
- Theophylline is pure form of drug
- Aminophylline is a mixture of Theophylline with Ethylenediamine
- Aminophylline is 20 times more soluble than Theophylline on its own
What formulation is
Aminophylline available as?
- Injection
- MR Tablet (Phyllocontin continus)
What formulation is
Theophylline available as?
- MR Tablet
- Nuelin SA
- Uniphylline continus - MR Capsules
- Slo-phyllin
NOTE: Theophylline is only MR oral preparation. If it is to be given as an injection, it would be given as Aminophylline
What is the therapeutic range of Theophylline?
-10-20mg/L
- Side effects can still occur during this range
- Frequency and severity of side effects increase when over 20mg/L
SE of theophylline < 20mg/L
- DNV
- Headache
- Tremor
SE of theophylline > 20mg/L
Overdose
- Severe vomiting
- Insomnia
- Agitation/Restlessness
- Dilated pupils
- sinus tachycardia/ arrythmias
- hyperglycaemia
- convulsions
- Severe hypokalaemia
Theophylline concentration is decreased in
- smokers
- alcohol consumption
- enzyme inducers (carbamazepine, rifampicin, phenytoin)
smoking is an enzyme inducer
Theophylline concentration is increased in
- heart failure
- hepatic impairment
- viral infection
- enzyme inhibitors (macrolides, cimetidine, cipro)
Interactions
Hypokalaemia
- CS
- SABA/LABA
- diuretics
- inducers
- lithium
Monitoring
- Plasma-theophylline concentration
- Aiming for 10-20mg - Plasma-Potassium
- Especially if concomitant administration with drugs that increase the risk of HYPOkalaemia
Check drug plasma levels
o Sample should be taken 4-6 hours after an oral dose
o 5 days after starting treatment
o At least 3 days after dose adjustment
Brands
- Brands do not have the same bioavailability
o Maintain the same brand
o Prescribe by brand
Theophylline and
Disulfiram
Disulfiram can increase the concentration of Theophylline leading to toxicity
Aminophylline dosage and obesity
- This only applies to aminophylline
- If a patient is OBESE, then use IDEAL BODY WEIGHT to avoid excessive dosage
Can Theophylline be taken in pregnancy and breastfeeding?
- Can be taken as normal in pregnancy & breastfeeding
- It is important that asthma is controlled in pregnancy
