Preservative free insulin formulations

1. An insulin formulation specifically adapted for aerosolization, the formulation comprising:

a major amount of water;

a minor amount of insulin;

a minor amount of HCl;

a minor amount of NaOH; and

2 to 4 Zn 2+ per insulin hexamer;

wherein the formulation is preservative free thereby facilitating aerosolization of the formulation as an aerosolized spray using a vibrating aperture plate having a plurality of apertures, and wherein the spray is produced without substantial foaming of the formulation when the formulation is held on a rear face of the aperture plate by gravity and the aerosolized spray exits a front face of the aperture plate solely by vibration of the aperture plate that is vibrated using an annular vibratable element that circumscribes the apertures.

2. An insulin formulation as in claim 1 , wherein the insulin has a concentration of about 100 IU/ml to about 1200 IU/ml of human insulin.

3. An insulin formulation as in claim 1 , wherein the water comprises in volume about 99.8% to about 97.0%, and the human insulin comprises in volume about 0.2% to about 3.0%.

4. An insulin formulation as in claim 1 , wherein the formulation does not include meta-cresol, cresol or phenol.

5. An insulin formulation as in claim 1

wherein the formulation is aerosolized as a spray without substantial foaming when the vibrating aperture plate vibrates at a frequency in the range from about 50 kHz to about 150 kHz, and wherein the amount of the insulin formulation has a volume of up to about 200 μL, and wherein the time to aerosolize at least 97% of the formulation is less than about 22 seconds.

6. An insulin formulation as in claim 1 , wherein the insulin formulation does not contain a preservative and thereby is aerosolized without substantial foaming of the formulation.

7. An insulin formulation as in claim 1 , wherein the amount of the insulin formulation has a volume of about 40 μL, to about 200 μL.

8. An insulin formulation as in claim 1 , wherein the amount of the insulin formulation has a volume of up to about 100 μL, and wherein the time to aerosolize at least 97% of the formulation is less than about 11 seconds.

9. An insulin formulation as in claim 1 , wherein the aperture plate is vibrated using the annular vibratable element with an amplitude that is less than about 2 μm.

10. An insulin formulation as in claim 1 , wherein the aerosolized spray comprises aerosolized droplets having a mean size in the range from about 3 μm to about 8 μm.

11. An insulin formulation as in claim 1 , wherein less than 3% of the formulation is converted to foam during aerosolization.