Using Salt Counterions to Modify β₂-Agonist Behavior in Vivo.

Area of Science:

• Pharmacology
• Drug Delivery
• Physical Chemistry

Background:

• Limited data exists on how salt counterions affect inhaled medicines' biological performance.
• Understanding counterion effects is crucial for optimizing inhaled drug efficacy.

Purpose of the Study:

• To investigate the influence of salt counterions on the tissue permeability and airway smooth muscle relaxation of salbutamol, formoterol, and salmeterol.
• To determine if specific counterions enhance the bronchodilator effects of these inhaled medications.

Main Methods:

• In vivo studies in guinea pigs to assess airway resistance and bronchodilator effects.
• In vitro studies using guinea pig tracheal sections to evaluate tissue transport and smooth muscle relaxation.
• Infrared spectroscopy to identify ion-pair formation between drugs and counterions.

Main Results:

• Salbutamol formulated with 1-hydroxy-2-naphthoate (1H2NA) showed superior bronchodilator effects (p < 0.05) compared to salbutamol base.
• The salbutamol:1H2NA combination demonstrated a significantly faster rate of tissue transport (p < 0.05).
• In vitro, salbutamol with 1H2NA exhibited greater inhibition of tracheal contraction (94.13%, p < 0.05) than salbutamol base.

Conclusions:

• The choice of counterion can significantly alter the in vivo biological performance of inhaled drugs like salbutamol.
• Ion-pair formation between salbutamol and 1H2NA modifies its physicochemical properties, leading to enhanced efficacy.
• Careful consideration of counterions is essential for developing effective inhaled pharmaceutical salts.