Methylxanthines RC 195

Types of Methylxanthines Caffeine Theobromine Theophylline Most common methylxanthine used in respiratory care

Methylxanthine Effects Bronchodilation Cerebral stimulation Skeletal muscle stimulation Vasodilator Cardiac stimulation Smooth muscle relaxation Diuresis

Theophylline Common Brands Aminophylline IV administration while hospitalized Oxtriphylline Oral form Choledyl, TheoBid, TheoDur Combinations (Theophylline and sympathomimetc) Oral preparations: Marax, Tedral, Quibron, Slo-Phylline

Theophylline Duration 3-9 ½ hours Is deactivated in liver Desired effects and side effects are determined by serum, ie plasma, levels

Signs that indicate need to check serum Theophylline levels N &V Thirst Agitation Arrhythmias

Factors that decrease Theophylline clearance CHF Pneumonia Pulmonary Edema Hepatic problems Drugs- eg, Cimetidine, Erythromycin, Propranolol These patients are prone to high serum levels and toxicity

Factors that increase Theophylline clearance Cigarette smoking Being a pediatric patient Acidosis These patients may need higher doses to achieve therapeutic levels

Routes and Dosages IV Loading dose is 6 mg/kg over thirty minutes (why?) or 3 mg/kg in a patient who has received Theophylline within last 24 hours Maintenance dose: .9 mg/kg/hour for person who smokes .5 mg/kg/hour for non-smoker .25 mg/kg/hour in a patient with decreased clearance

Routes and Dosages (cont.) Oral – 100-200 mg TID or QID TheoBid and Theodur are BID Rectal – 500 mg IM – 250-500mg Very painful so not a commonly used route Theophylline is rarely aerosolized! Variable serum levels and intense coughing

Drug Interactions Antagonizes Propranolol Potentiates sympathomimetics Additive with diuretics Antibiotics – variable. May also cause precipitation if mixed in same IV line It is best to administer IV Theophylline in its own IV line

Time for a case study!