Theophylline Flashcards
What two formulations are given for theophylline?
PO
IV
What is the percentage of absorption for theophylline PO?
100%
What is the percentage of absorption for theophylline IV?
80%
Is it best for theophylline to be administered with food or without food? Why or why not?
Without food - can increase the absorption and toxicities with food
What is the volume of distribution (Vd) for theophylline?
0.4 to 0.6 L/kg
Where is theophylline mainly metabolized?
Hepatic metabolism (> 90%) FYI = CYP1A2 (mainly), 3A4, 2E1
(T/F) - Smoking cessation (stopped smoking) can decrease theophylline concentration
FALSE - it increases concentrations
Where is theophylline eliminated/excreted?
10% unchanged in urine
Are renal dose adjustments needed for the theophylline in renal failure patients?
No
Is theophylline given before or after hemodialysis (HD)?
After - eliminated by HD
What is the half-life of theophylline?
T 1/2 = 5 to 24 hours
In which 2 patient populations is theophylline’s half-life prolonged?
- Premature or mature neonates
- Patients > 65 yo
What 4 things can increase theophylline clearance?
- Inducers of CYP1A2 and 3A4
- Hyperthyroidism
- Diet charbroiled foods
- Low CHO/high protein diet
Name 5 inducers of CYP1A2 and 3A4
- Smoking (any type of smoking)
- Carbamazepine
- Phenobarbital
- Phenytoin
- Rifampin
What 5 things can decrease theophylline clearance?
- Inhibitors of CYP1A2 and 3A4
- Cirrhosis or acute hepatitis
- Heart failure
- Hypothyroidism
- Low protein/high CHO
Name 6 inhibitors of CYP1A2 and 3A4
- Ciprofloxacin
- Macrolides
- Azole antifungals
- Oral contraceptives
- Protease inhibitors
- Verapamil
What are the names of the extended-release theophylline tablets and capsules?
Theo-24
Theocron
Theo-Dur
Is theophylline a prodrug in the IV form?
YES
There are two general dosing rules, name 1 regarding the weight that should be used to calculate doses
Use TBW (Act. BW) for dosing unless the patient is obese, then use the IBW
There are two general dosing rules, name 1 regarding the blood concentration
For every 1 mg/kg of theophylline, blood concentrations will rise ~ 2 mg/L
What is the maintenance dose (MD) of theophylline orally given in most patients (healthy)? What is the max dose?
10 mg/kg/day
Max = 900 mg/day
What is the MD of theophylline orally given in patients who have HF or liver dysfunction?
5 mg/kg/day
Max = 400 mg/day
What is the MD of theophylline given IV?
0.5 mg/kg/hr
What is the therapeutic range of serum concentrations in adults taking theophylline?
5 to 15 mg/L
Is it acceptable for serum concentrations to reach 20 mg/L?
Yes - in some patients
What is the therapeutic range of serum concentrations in neonates taking theophylline?
6 to 13 mg/L
In normal serum concentrations, what side effects can occur?
- N/V
- Dyspepsia
- Nervousness
- Insomnia
- HA
- Tachycardia
What side effects can occur in serum concentrations ranging from 20 to 30 mg/L?
Tachyarrhythmias
What side effects can occur in serum concentration > 40 mg/L?
- Life threatening arrhythmias
- Seizures
