Suspension formulations

Abstract

The present invention relates to suspension formulations, especially those for delivering a pharmaceutically active agent in aerosol form using a spray or aerosol device, such as a pressurised metered dose inhaler (pMDI). The formulations may be for pulmonary, nasal, buccal or topical administration, but are preferably for pulmonary inhalation.

Description

[0001]The present invention relates to suspension formulations, especially those for delivering a pharmaceutically active agent in aerosol form using a spray or aerosol device, such as a pressurised metered dose inhaler (pMDI). The formulations may be for pulmonary, nasal, buccal or topical administration, but are preferably for pulmonary inhalation.BACKGROUND TO THE INVENTION[0002]Since the pMDI was introduced in the mid 1950s, inhalation has become the most widely used route for delivering bronchodilator drugs and steroids to the airways of asthmatic patients. Compared with oral administration of bronchodilators, inhalation offers a rapid onset of action and a low instance of systemic side effects. More recently, inhalation from a pressurized inhaler has been a route selected for the administration of other drugs.[0003]The pMDI is dependent upon the propulsive force of a propellant system used in its manufacture to dispense the drug formulation from the device in a form that may b...

AI Technical Summary

Benefits of technology

The present invention relates to a composition that can be delivered by a pressurised metered dose inhaler. The composition consists of a suspension of a pharmaceutical agent in propellants, which also contains one or more suspension stabilizers to keep the active agent in a physical state. The suspension stabilizer may or may not be insoluble. The technical effect of this invention is to provide a more stable and consistent composition for delivery using a pressurised metered dose inhaler.

Problems solved by technology

However, it has been found that such hydrocarbons have low densities relative to the pharmaceutically active agents included in the formulations.

Where suspension formulations are prepared using such propellants, the formulations sediment rapidly and are unacceptable.

Furthermore, the solubility of many drugs in these hydrocarbons is poor, which means that it is difficult to prepare formulations that are solutions which contain suitable amounts of drug.

Most pharmaceutically active agents are not sufficiently soluble in pure propellants, either HFAs or CFCs, for simple two component formulations of active agent and propellant to be practical.

Controlling the size of the particles in an aerosol spray produced from a purely liquid formulation is more difficult than it is with a formulation comprising a suspended solid particulate pharmaceutically active agent.

For example, most pharmaceutically active compounds are much more susceptible to degradation by acid or alkali when in solution than they are when solid.

It is also simply impossible to render many pharmaceutically active agents sufficiently soluble in a pharmaceutically acceptable propellant system, for a solution formulation to be a realistic option for them.

However, not all active agents are stable when in solution or in direct contact with the excipients and propellant.

However, high levels of ethanol may impart a negative effect on a suspension system by dissolving the drug.

However, one of the problems which has arisen in the development of HFA-based suspension formulations for use in pMDI and like devices, is that many of the surfactants commonly employed as dispersing agents in CFC-based formulations are substantially insoluble in HFA 134a and HFA 227 and, thus, are substantially ineffective in simple formulations based on these latter two propellants, or other HFA propellants.

This phenomenon is especially disadvantageous in formulations for delivery into the lungs because, over time, it causes the particles of active agent in the formulation to grow, possibly to a size in excess of that generally considered to be acceptable for inhalation, i.e., to have a MMAD of greater than 10 μm.

Further disadvantages associated with the use of ethanol as a co-solvent include its potential toxicity, its capacity to increase a formulation's propensity to absorb water and the fact that many patients dislike the taste that its presence can impart to a formulation.

Although the literature suggests (see WO 92 / 08447 and WO 91 / 04011) that formulations prepared in this manner are effective, in the sense that they allow stable dispersions of powdered active agent to be formed in the HFA propellant, it has so far not proven possible, in practice, to manufacture useful formulations in this way.

For example, it is difficult to achieve a uniform coating using techniques of this nature because the manner in which the dispersing agent precipitates from the evaporating solvent can be unpredictable.

A further problem that is often associated with known formulations for delivery using devices such as pMDIs is their stability and consequently their shelf life.

These formulations and the pMDI products have a reduced shelf life due to moisture ingress.

However, once opened from their foil packaging, the shelf life of the pMDI formulation is dramatically reduced due to the ingress of moisture.

The ingress of moisture can change the suspension characteristics, often leading to increased flocculation rate which leads to poor product performance and poor drug delivery.