Theophylline PK

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What are some common uses of theophylline?
- Asthma
- COPD: emphysema, chronic bronchitis
- Premature apnea: CNS stimulant
What is the M.O.A of theophylline?
- Bronchodilation: antagonises adenosine receptors and inhibits phosphidesterase (increase cAMP)
- Anti-inflammatory
- Enhances contractile ability of the diaphragm: helps break up the mucus in the lungs
What is the LD for theophylline in patients who have not received theophylline for 24 hours?

4-6 mg/kg
What is the LD for theophylline in patients who have already received the drug within the last 24 hours?
- 2-3 mg/kg
- Or no LD
What type of product must be used to give a LD?
- IV
- Rapid-release oral products
What is the salt factor for aminophylline?

0.8
How often do you have to dose immediate-release tablets of theophylline?

q 6-8 hours
How often do you have to dose extended release tablets/capsules of theophylline?

BID
What type of body weight should be used when dosing theophylline?
- ACTUAL
- Unless the patient is > 30% IBW then use IBW
Approximately how large of a rise in the serum concentration of theophylline would you expect to see with every 1 mg/kg of theophylline given?

~ 2 mg/L
What is the oral maintenance dose for theophylline?

10 mg/kg/day
What is the max dose for oral theophylline?
- 900 mg/daily
- (400 mg/day in patients with HF or renal dysfunction)
What is the adjusted MD for patients with HF or liver dysfunction?

5 mg/kg/day
What is the IV MD of theophylline?

0.5 mg/kg/hr continuous infusion
What is the goal therapeutic range in adults on theophylline?

5-15 mg/L
What is the goal therapeutic range in neonates on theophylline?

6-13 mg/L
When giving a LD, when should a blood level be drawn?

30 minutes after the LD is given
When should you monitor the blood level of theophylline?

12-24 hours after administration
What are some AE seen with theophylline when in the therapeutic range?
- N/V/D
- Insomnia
- Nervousness
- Headache
- Tachycardia
- Seizures (occur without any other SE and may not respond to anti-epileptic drugs)
What AE is seen when the theophylline blood concentration is 20-30 mg/L?

Tachyarrhythmias
What AE is seen when serum concentrations of theophylline exceed 40 mg/L?

Life threatening arrhythmias: ventricular tachycardia, fibrillations or PVCs; seizures
What is the % of theophylline bound to plasma proteins?

40%
Does theophylline have a large or small volume of distribution?

Small
What is the major CYP enzyme involved in metabolism of theophylline?

1A2
What % of theophylline metabolism is hepatic?

90%
What are the three types of metabolism that theophylline undergoes?
- hydroxylation
- demethylation
- methylation
Why does theophylline have to be renally adjusted in neonates?

Because it is not demethylated therefore 50% of the drug is excreted unchanged via the kidneys
Can theophylline be removed by hemodialysis?

Yes
When should theophylline be dosed in relation to hemodialysis?

After
What can vary the clearance of theophylline?

Age
In what patient population is the clearance of theophylline accelerated?

Children between 1-9
In what patient population is the clearance of theophylline slower?
- neonates
- premature neonates
- Patients > 65 y/o
What are some inducers of 1A2 that will increase the clearance of theophylline?
- Smoking (tobacco and marijuana)
- Phenytoin
- Carbamazepine
- Phenobarbital
- Rifampin
What are some things that increase the clearance of theophylline?
- Hyperthyrodism
- Diet (high in charbroiled foods)
What are some inhibitors of 1A2 that will decrease the clearance of theophylline?
- Ciprofloxacin
- Azoles
- Clarithromycin, Erythrmoycin
- Telithromycin
- Protease inhibitors
- Verapamil
- Oral Contraceptives
What are some other factors that will decrease the clearance of theophylline?
- Cirrhosis
- Acute hepatitis
- Heart failure
- Hypothyroidism
- Diet (Atkins : low carbs, high protein)

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rclee06

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Theophylline PK

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Updated

2012-04-28T01:47:25Z

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