what respiratory diseases are Xanthines used for ?
relax and open airway passages in lungs
-asthma-maintenance therapy:mild, persistent (theophylline)
-COPD- alternative to B2 agonist and anticholinergic, NOT for acute exacerbations (theophylline)
-Apnea of prematurity (caffeine citric)
how are theophyllines administered?
-tablets for oral
-injections
-suppositories
the xanthine of choice to treat apnea of prematurity is
IV or oral caffeine citrate
-stimulates breathing of neonates until CNS matures
-first choice when non-pharmacological methods unsuccessful
caffeine citrate dosing levels for Apnea of prematurity
loading dose: 20 mg/kg
maintenance dose: 5mg/kg
therophylline and caffeine are examples of
xanthines agents: methylxanthines
*what are the physiologic effects produced by xanthines
-CNS stimulation
-cardiac muscle stimulation
-diuresis
-bronchial,uterine and vascular smooth muscle relaxation
-peripheral and coronary vasodilation
-cerebral vasoconstriction
why is it difficult to determine dosing for theophyllines?
-metabolism
*age, smoking status, concurrent medication
-clearance rate
-narrow therapeutic margin
*benefit vs toxic side effect
*difficult to determine therapeutic doses
*dosage schedule are used
what are the side effects of theophylline often seen in pt
-gastric upset
-headache
-diuresis
-vomiting
-tachycardia
-tachypnea
serum levels of theophylline and effects ( overdose symptoms)
- <5ug/mL=no effects seen
- 10-20ug/mL: therapeutic range
- > 20ug/mL. nausea
- > 30ug/mL: cardiac arrhythmias
- 40-55ug/mL: seizures
serum levels of theophylline for asthma and COPD
asthma: 5-15ug/mL
COPD: 5-10ug/ mL
factors affecting theophylline activity
-liver and kidney functions
-interactions w/other drugs
-smoking(decrease levels) and viral infections (increase levels)
