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

TheophyllineCommon 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!