Maxivent Mechanism of Action

Bronchodilator.
Pharmacology: Pharmacodynamics: Doxofylline is a novel bronchodilator xanthine that differs from theophylline for the presence of a dioxalane group in position 7. Like theophylline, Doxofylline's mechanism of action is related to the inhibition of phosphodiesterase activities. However, differently from theophylline, Doxofylline appears to have decrease affinities towards adenosine A1 and A2 receptors, which may account for the better safety profile of the drug.
Pharmacokinetics: The half-life of Doxofylline is greater than six hours; so as to allow effective constant plasma levels with a t.i.d. dose regimen. Single dose pharmacokinetic studies in man after oral and intravenous administration defined distribution and absorption of the drug.
After i.v. administration of 100 mg to 5 healthy volunteers, distribution of Doxofylline in plasma followed a bi-compartmental model. During the distribution phase the plasma AUC was only a modest portion of the total AUC; plasma clearance was somewhat high, ranging from 444 mL/min to 806 mL/min; apparent volume of distribution was about 1 L/kg. The mean half-life after i.v. administration was about 65 min. (from 40 min to 96 min). After oral administration (tablets), peak plasma levels were reached after one hour. Absolute bioavailability is about 62.6%; at pH 7.4 plasma proteins binding the compound is about 48%. Less than 4% of an orally administered dose is excreted unchanged in the urine.
Doxofylline is almost completely metabolized in the liver (90% of the total drug clearance).
Hydroxyethyltheophylline is the only detectable circulating metabolite of Doxofylline.
After repeated administrations Doxofylline reaches the steady state in about 4 days; the elimination half-life during long-term treatment is 8-10 hours: this allows a twice-daily dose regimen. No accumulation of the drug was noted after one week of treatment.