Theophylline Derivatives

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Theophylline Action/Kinetics: Theophyllines stimulate the CNS, directly relax the smooth muscles of the bronchi and pulmonary blood vessels (relieve bronchospasms), produce diuresis, inhibit uterine contractions, stimulate gastric acid secretion, and increase the rate and force of contraction of the heart. Response to the drugs is highly individualized. The-ophylline is well absorbed from un-coated plain tablets and PO liquids. Theophylline salts: Onset: 1—5 hr, depending on route and formulation. Therapeutic plasma levels: 10—20 mcg/mL. tV2: 3—15 hr in nonsmoking adults, 4—5 hr in adult heavy smokers, 1—9 hr in children, and 20—30 hr for premature neo nates. An increased tV2 may be seen in individuals with CHF, alcoholism, liver dysfunction, or respiratory infections. Because of great variations in the rate of absorption (due to dosage form, food, dose level) as well as its extremely narrow therapeutic range, theophylline therapy is best monitored by determination of the serum levels. If these determinations cannot be obtained, saliva (contains 60% of corresponding theophylline serum levels) determinations can be used. Eighty-five percent to 90% metabolized in the liver and various metabolites, including the active 3-methylxanthine. Theophylline is metabolized partially to caffeine in the neonate. The premature neonate excretes 50% unchanged theophylline and may accumulate the caffeine metabolite. Excretion is through the kidneys (about 10% unchanged in adults).

Uses: Prophylaxis and treatment of bronchial asthma. Reversible bron-chospasms associated with chronic bronchitis, emphysema, and COPD. Non-FDA Approved Uses: Treatment of neonatal apnea and Cheyne-Stokes respiration.

Contraindications: Hypersensitiv-ity to any xanthine, peptic ulcer, seizure disorders (unless on medication), hypotension, CAD, angina pectoris.

Special Concerns: Use during lactation may result in irritability, insomnia, and fretfulness in the infant. Use with caution in premature infants due to the possible accumulation of caffeine. Xanthines are not usually tolerated by small children because of excessive CNS stimulation. Geriatric clients may manifest an increased risk of toxicity. Use with caution in the presence of gastritis, alcoholism, acute cardiac diseases, hypoxemia, severe renal and hepatic disease, severe hypertension, severe myocar-dial damage, hyperthyroidism, glaucoma.

Side Effects: Side effects are uncommon at serum theophylline levels less than 20 mcg/mL. At levels greater than 20 mcg/mL, 75% of individuals experience side effects including N&V, diarrhea, irritability, insomnia, and headache. At levels of 35 mcg/mL or greater, individuals may manifest cardiac arrhythmias, hypotension, tachycardia, hyperglycemia, seizures, brain damage, or death. Oral: Bitter taste, dry mouth. GI: N&V, diarrhea, anorexia, epigastric pain, hematemesis, dyspepsia, rectal irritation (following use of suppositories), rectal bleeding, gastroesopha-geal reflux during sleep or while recumbent (theophylline). CNS: Headache, insomnia, irritability, fever, dizziness, lightheadedness, vertigo, reflex hyperexcitability, seizures, depression, speech abnormalities, alternating periods of mutism and hy-peractivity, brain damage, death. CV: Hypotension, life-threatening ventricular arrhythmias, palpitations, tachycardia, peripheral vascular collapse, extrasystoles. Renal: Proteinuria, excretion of erythrocytes and renal tubular cells, dehydration due to diuresis, urinary retention (men with prostatic hypertrophy). Other: Ta-chypnea, respiratory arrest, fever, flushing, hyperglycemia, antidiuretic hormone syndrome, leukocytosis, rash, alopecia. Drug Interactions Barbiturates / i Theophylline levels Benzodiazepines / Sedative effect may be antagonized by theophy-lline

Carbamazepine / Either T or i the-ophylline levels

Cimetidine / T Theophylline levels Ciprofloxacin / T Plasma levels of theophylline with T possibility of side effects

Corticosteroids / T Theophylline levels

Ephedrine and other sympathomi-metics / T Theophylline levels Erythromycin / T Effect of theophylline due to i breakdown by liver Halothane / T Risk of cardiac arrhythmias

Ketamine / Seizures of the extensor-type

Ketoconazole / i Theophylline levels

Muscle relaxants, nondepolarizing / Theophylline i effect of these drugs Phenytoin / i Theophylline levels Propofol / Theophyllines i sedative effect of propofol

Quinolones / T Theophylline levels Sympathomimetics / i Theophylline levels

Tetracyclines / T Risk of theophy-lline toxicity

Troleandomycin / T Effect of the-ophylline due to i breakdown by liver

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Beat The Battle With The Bottle

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