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the onset of the bronchodilative action was observed at 1-5 min after inhalation in conscious guinea pigs and anesthetized dogs, indicating much faster onset of action than the tablet formulation.
Inhaled procaterol hydrochloride dilates not only the central airway but also peripheral airways in pediatric asthma patients.
Duration of Bronchodilative Action: Procaterol hydrochloride had a longer duration of bronchodilative action than isoproterenol, trimetoquinol, orciprenaline and salbutamol in dogs, cats and guinea pigs.
The potency with which procaterol hydrochloride at 10 mcg by inhalation inhibited the increase in airway resistance due to histamine was equal to that of salbutamol at 200 mcg by inhalation in anesthetized dogs. However, procaterol hydrochloride is longer-acting than salbutamol.
Selectivity for β2-Adrenergic Receptors (Organ Selectivity): The selectivity of procaterol hydrochloride for β2-adrenergic receptors in the respiratory system greater than that for such receptors in the cardiovascular system, as compared to isoproterenol, trimetoquinol, orciprenaline and salbutamol in dogs, cats and guinea pigs.
Antiallergic Action: Procaterol hydrochloride exhibited a definite antiallergic action by inhibiting antigen-induced increase in airway resistance, the PCA reaction and histamine release from sensitized lung tissues in guinea pigs and rats, as well as allergen-induced skin reactions, and increases in asthmatic responses to allergen inhalation in bronchial asthma patients, as compared to isoproterenol, trimetoquinol, orciprenaline sulfate and salbutamol sulfate.
The drug also inhibited allergen-induced delayed-type and immediate-type bronchial responses.
Effects on Respiratory Tract System: Procaterol hydrochloride accelerated ciliary activity in the airway of pigeons.
Effect on Exercise-Induced Asthmatic Attacks: Procaterol hydrochloride suppressed treadmill or ergometer exercise- or methacholine-induced asthmatic attacks in patients with bronchial asthma.
Effect on Airway Hypersensitivity: Procaterol hydrochloride inhibited airway hypersensitivity induced by the inoculation of influenza virus C in dogs.
Effect on Vascular Permeability Increase: Procaterol hydrochloride inhibited the acceleration of vascular permeability and edema formation in dorsal subcutaneous air sacs in rats experimentally prepared using various inflammatory chemical agents. Its potency was similar to that of isoproterenol. Procaterol hydrochloride also inhibited pulmonary edema induced by histamine inhalation in guinea pigs, with greater potency than salbutamol sulfate.
Effect on Cough: Procaterol hydrochloride hydrate inhibited substance P-induced cough in normal subjects with upper respiratory tract infection.
Clinical Studies: Meptin 50 mcg tablets were studied in a total of 1,362 patients at 212 institutions throughout Japan. The clinical efficacy rates of the drug administered by single and repeated administration in patients with bronchial asthma were 51.1% (310/607) and 40.1% (188/469), respectively. The efficacy rate for repeated administration in patients with chronic bronchitis or pulmonary emphysema was 20.2% (19/94), and the corresponding value in patients with acute bronchitis was 50% (36/72). Tolerance to the drug was not observed during repeated administration.
Meptin 25 mcg tablets were studied in children with bronchial asthma. The clinical efficacy of the drug single and repeated administration was 59.4% (199/335) and 48% (145/302), respectively. The efficacy of the drug by repeated administration in those with acute bronchitis was 94% (79/84). Tolerance to the drug was not observed during repeated administration.
Meptin syrup was studied in children. The clinical efficacy of the drug by single administration in those with bronchial asthma was 82.9% (34/41), the efficacy by repeated administration in those with bronchial asthma or asthma-like bronchitis was 50.7% (116/229) and the efficacy by repeated administration in those with acute bronchitis was 75.9% (104/137).
Pharmacokinetics: Plasma Concentrations: When Meptin tablet was administered orally to a 6 healthy male subjects as single doses of 50 mcg/subject and 100 mcg/subject, the following plasma concentration curves and pharmacokinetic parameters were obtained. (See Figure 1.)
Plasma Pharmacokinetic Data: 50 mcg tablet: Time to reach maximum plasma concentration (tmax) is 1.1 hr, peak plasma concentration (Cmax) is 97 pg/mL and half-life (t½) is not determined.
100 mcg tablet: Tmax is 1.5 hrs, Cmax is 226 pg/mL and t½ is 3.6 hrs.
When Meptin syrup was administered orally to 44 healthy male subjects at a single dose of 100 mcg/subject as procaterol hydrochloride, in a fasting condition, the following plasma concentration curves and pharmacokinetic parameters were obtained. (See Figure 2.)
Pharmacokinetic parameters of procaterol syrup: Tmax is 1.3±0.7 hrs, Cmax is 263±104 pg/mL, t½ is 41±1.8 hrs and area under the concentration-time curve (AUC) is 1,151±288 pg·hr/mL.
Urinary Excretion: When Meptin was administered orally as single doses of 50 and 100 mcg/subject as procaterol hydrochloride, 9.93% and 11.65% of the dose were excreted into the urine within 24 hrs post-dosing, respectively.
