Theophylline

INTRODUCTION

Indications

Long-term control of reversible airway obstruction caused by asthma or COPD.

Action

Inhibit phosphodiesterase, producing increased tissue concentrations of cyclic adenosine monophosphate (cAMP). Increased levels of cAMP result in Bronchodilation, CNS stimulation, Positive inotropic and chronotropic effects, Diuresis, Gastric acid secretion. Therapeutic Effects: Bronchodilation.

Adverse Reactions/Side Effects

CNS: SEIZURES, anxiety, headache, insomnia, irritability. CV: ARRHYTHMIAS, tachycardia, angina, palpitations. GI: nausea, vomiting, anorexia. Neuro: tremor.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Be alert for new seizures or increased seizure activity, especially at the onset of drug treatment. Document the number, duration, and severity of seizures, and report these findings to the physician immediately.

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report a rapid heart rate (tachycardia) or signs of other arrhythmias, including palpitations, chest pain, shortness of breath, fainting, and fatigue/weakness.

• Assess pulmonary function periodically by measuring lung volumes, breath sounds, respiratory rate, and other symptoms (wheezing, dyspnea, shortness of breath) (See Appendixes I, J, K). Report changes in pulmonary function to help document the effects of drug therapy in treating or preventing bronchoconstriction.

• Monitor and report signs of CNS toxicity, including tremor, anxiety, irritability, or other changes in mood or behavior. Sustained or severe CNS signs may indicate overdose or excessive use of this drug.

Interventions

• Because of the risk of cardiovascular stimulation, use caution during aerobic exercise and endurance conditioning. Assess exercise tolerance frequently (blood pressure, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

Patient/Client-Related Instruction

• Because of the risk of cardiovascular and CNS stimulation, caution patient to avoid taking more than the recommended dose. Instruct patient to contact physician immediately if bronchospasm is not relieved by medication or worsens after treatment.

• Advise patient to minimize intake of caffeine or other xanthine-containing foods or beverages (colas, coffee, tea, chocolate) and to reduce intake of charcoal-broiled foods.

• Instruct patient and family/caregivers to report other troublesome side effects such as severe or prolonged headache, sleep loss, skin rash, or GI problems (nausea, vomiting, loss of appetite).

Pharmacokinetics

Absorption: Well absorbed from PO dosage forms; absorption from extended-release dosage forms is slow but complete.

Distribution: Widely distributed; crosses the placenta and into breast milk; does not distribute into adipose tissue.

Metabolism and Excretion: 90% metabolized by the liver to several metabolites (including the active metabolites, caffeine and 3-methylxanthine); metabolites are ...