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Albuterol has been shown in most clinical trials to have more bronchial smooth muscle relaxation effect than isoproterenol at comparable doses while producing fewer cardiovascular effects. However, all beta-adrenergic drugs, including albuterol sulfate, can produce a significant cardiovascular effect in some patients (See PRECAUTIONS). Pharmacokinetics Albuterol is longer acting than isoproterenol in most patients because it is not a substrate for the cellular uptake processes for catecholamines nor for metabolism by catechol-0-methyl transferase. Instead, the drug is conjugatively metabolized to albuterol 4'-0-sulfate. In a pharmacokinetic study in 12 healthy male volunteers of two inhalations of albuterol sulfate, 103 mcg dose/ inhalation through the mouthpiece, peak plasma albuterol concentrations ranging from 419 to 802 pg/ mL (mean 599 ± 122 pg/ mL) were obtained within three hours post-administration. Text Continues Below
Following this single-dose administration, 30. 8 ± 10. 2% of the estimated mouthpiece dose was excreted unchanged in the 24 hour urine. Since albuterol sulfate is rapidly and completely absorbed, this study could not distinguish between pulmonary and gastrointestinal absorption. Intravenous pharmacokinetics of albuterol were studied in a comparable group of 16 healthy male volunteers; the mean terminal half-life following a 30-minute infusion of 1.5 mg was 3.9 hours with a mean clearance of 439 mL/ min/ 1.73 m 2 . Intravenous albuterol studies in rats demonstrated that albuterol crossed the blood-brain barrier and reached brain concentrations amounting to about 5% of the plasma concentrations. In structures outside the blood-brain barrier (pineal and pituitary glands), the drug achieved concentrations more than 100 times those in whole brain. Studies in pregnant rats with tritiated albuterol demonstrated that approximately 10% of the circulating maternal drug was transferred to the fetus. Disposition in fetal lungs was comparable to maternal lungs, but fetal liver disposition was 1% of maternal liver levels. Page: << Prev | 1 | 2 | 3 | 4 | 5 | Next >>
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