Physical properties of aerosolized immunoglobulin for inhalation therapy

Animal studies suggest that passive immunization by intratracheal application of gammaglobulins may succeed in treating small children and infants with severe lower respiratory tract infection caused by respiratory syncytial virus (RSV). Since proteins foam easily when stirred up or used with compressed air, the feasibility of nebulization of the immunoglobulin solution (IVIG, Sandoglobulin) had to be tested. The therapeutic effect of a drug delivered via inhalation is proportional to the mass of aerosol deposited in the lungs. For a fixed breathing pattern, the amount deposited per unit of time in the thoracic region depends on mass flow rate and distribution of aerosol mass by droplet size. Both these variables were determined in relation to the weight concentration (osmolality), viscosity, and surface tension of the IVIG solution for four compressed air nebulizers. The mass flow rate of the spray decreases as the weight concentration of the solution increases, but droplet size distribution does not change. If the IVIG solution does not exceed 5% and the airflow rate is 6 L/min, a mass flow of about 150 mg to 250 mg (7.5 to 12.5 mg IVIG) per minute is obtained, depending on the physical characteristics of the nebulizer used. Low mass median diameter of about 2 microns and a mass distribution with a high percentage of the droplets below 6 microns will allow optimum intrapulmonary deposition in infants.