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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!