Respiratory tract deposition of sodium cromoglycate is highly dependent upon technique of inhalation using the Spinhaler.

Sodium cromoglycate deposition has been studied following delivery of the drug by inhalation to six normal volunteers and two groups of ten patients using the Spinhaler. Plasma concentrations of the drug, and its urinary excretion have been related to the inhalation technique used for its delivery. An early peak concentration of sodium cromoglycate occurred in the plasma, thereafter the plasma concentration declined mono- or bi-exponentially with a terminal T1/2 of approximately 100 minutes in both patients and normal subjects. There was a marked between-subject variability in the plasma concentrations of sodium cromoglycate achieved, and in the areas under the plasma concentration-time curves of the drug. This reflects the variability between subjects in the amount of drug delivered to the respiratory tract. Most of this variability was due to differences in inhalation technique particularly with regard to inspiratory flow rate achieved and duration of breath-holding after inhalation. Thus careful instruction of patients is required to derive optimal dosing with sodium cromoglycate. It is recommended that patients inhale through the Spinhaler as rapidly as possible and then breath-hold for 10 seconds. These data provide a valuable background against which to study the relationship between the disposition of sodium cromoglycate, its site of action and its efficacy.