DRYING OF PHARMACEUTICAL POWDERS
The present invention relates to a method for drying the residual solvent content of a pharmaceutical product or powder. The present disclosure describes a method that allows fast drying of fine and cohesive pharmaceutical powders enabling it uses for batch, semi-continuous and continuous operation.
1 . A method for drying the residual solvent content of a pharmaceutical product in the form of a powder, comprising:
i) feeding the pharmaceutical powder into a drying chamber;
ii) feeding a gas stream across a powder bed in the drying chamber; and
iii) providing a permeable element to support the powder bed,
wherein the gas stream flows, first through the powder bed and then the permeable element, downwards, upwards or radially.
2 . The method according to claim 1 , wherein the powder has a Dv50 of <100 m and a bulk density of <0.6 g/ml.
3 . The method according to claim 1 , wherein the gas stream flows downwards through the powder bed.
4 . The method according to claim 1 , wherein the pharmaceutical product is an amorphous material produced by spray drying or any known drying technology, and preferably wherein the pharmaceutical product is an amorphous material produced by spray drying.
5 . The method according to claim 1 , wherein the permeable element comprises a filter or a porous membrane.
6 . The method according to claim 1 , wherein:
(i) the gas stream is heated prior to feeding it into the drying chamber; and/or
(ii) the drying chamber surface is heated to the target drying temperature.
7 . The method according to claim 1 , wherein the gas stream is fed at a flowrate sufficient to cause the powder bed to be pushed against the permeable element to maximize relative velocity between the gas and the powder.
8 . The method according to claim 1 , wherein:
(i) the ratio between the gas flowrate and product mass is at least 0.4 kg/h of gas per 1 kg of product; or
(ii) the ratio between the gas flowrate and product mass is in the range of about 0.4 kg/h to about 36 kg/h of gas per 1 kg of product.
9 . The method according to claim 1 , wherein the relative velocity between the gas and the powder is at least 0.05 cm/s, optionally the relative velocity between the gas and the powder is in the range of about 0.05 to 0.25 cm/s.
10 . The method according to claim 1 , wherein:
(i) the temperature of the gas stream is between the room temperature and the melting temperature or the glass transition temperature of the pharmaceutical product; and/or
(ii) the gas is selected from a group consisting of: nitrogen (N2), carbon-dioxide (CO2), air and mixtures thereof.
11 . The method according to claim 1 , wherein the gas pressure is periodically changed, from vacuum to pressure up to 10 bar, and preferably wherein the gas pressure is between 2-10 bar and is periodically changed.
12 . The method according to claim 1 , wherein:
(i) the permeable element is made of a material selected from the group consisting of: PTFE (Teflon), PP, PVDF, PCTE and combinations thereof;
(ii) the permeable element is supported or replaced by a sintered metal or polymer plate; and/or
(iii) the method further comprises vibrating or agitating the drying chamber to mitigate clogging of the powder in the permeable element.
13 . The method according to claim 1 , wherein the permeable element has porosities in the range of about 0.2 μm to about 2 μm or 0.2 μm to about 1 μm.
14 . The method according to claim 1 , wherein the method is a batch process, using a single unit, a semi-continuous process by combining at least two units in parallel, or a fully continuous process.
15 . (canceled)