醫學三：80題 ( 包括內科,家庭醫學科等科目及其相關臨床實例與醫學倫理 )題庫下載題庫

Metabolism
Theophylline does not undergo any measurable first-pass elimination. In adults and children older than 1 yr of age, about 90% of the dose is metabolized in the liver. Caffeine and 3-methylxanthine are the only theophylline metabolites with pharmacologic activity.

Elimination
Excretion is via the kidneys. In neonates, approximately 50% of a theophylline dose is excreted unchanged in urine. Beyond 0 to 3 mo, 10% of a theophylline dose is excreted unchanged in urine.

Special Populations
Renal Function Impairment

No dosage adjustment is required for renal function impairment in adults a...

Metabolism
Theophylline does not undergo any measurable first-pass elimination. In adults and children older than 1 yr of age, about 90% of the dose is metabolized in the liver. Caffeine and 3-methylxanthine are the only theophylline metabolites with pharmacologic activity.

Elimination
Excretion is via the kidneys. In neonates, approximately 50% of a theophylline dose is excreted unchanged in urine. Beyond 0 to 3 mo, 10% of a theophylline dose is excreted unchanged in urine.

Special Populations
Renal Function Impairment

No dosage adjustment is required for renal function impairment in adults and children older than 3 mo of age. In neonates with reduced renal function, dose reduction and frequent monitoring of serum concentrations is required.

Hepatic Function Impairment
A prolonged t ½ may occur in liver dysfunction.

Pharmacokinetics vary widely among similar patients and cannot be predicted by age, sex, body weight, or other demographic characteristics. A prolonged t ½ may occur in CHF, alcoholism, and respiratory infections.

Allopurinol, nonselective beta-blockers, calcium channel blockers, cimetidine, oral contraceptives, corticosteroids, disulfiram, ephedrine, influenza virus vaccine, interferon, macrolide antibiotics (eg, erythromycin), mexiletine, quinolone antibiotics (eg, ciprofloxacin), thyroid hormones
Increase theophylline levels.

Aminoglutethimide, barbiturates, hydantoins, ketoconazole, rifampin, smoking (cigarettes and marijuana), sulfinpyrazone, sympathomimetics
Decrease theophylline levels.