Liquisolid Techniques Lab Report

2.5 LIQUISOLID TECHNIQUE

2.5.1 Introduction [14]

With the liquisolid technology, a liquid may be transformed into a free flowing, readily compressible and apparently dry powder by simple physical blending with selected excipients named the carrier and coating material. The liquid portion, which can be a liquid drug, a drug suspension or a drug solution in suitable non-volatile liquid vehicle, is incorporated into the porous carrier material. Fig. 2.7 Liquisolid System Representation

The liquisolid compacts are acceptably flowing and compressible powdered forms of liquid medications. The term liquid medication refers to liquid lipophilic drugs or water-insoluble solid drugs dissolved in suitable water-miscible non-volatile solvent systems

To calculate the required amounts of powder excipients (carrier and coating materials) a mathematical approach for the formulation of liquisolid systems has been developed by Spireas. This approach is based on the flowable (Ф-value) liquid retention potential introducing constants for each powder/liquid combination. The Ф-value of a powder represents the maximum amount of a given non-volatile liquid that can be retained inside its bulk [w/w] while maintaining an acceptable flowability. The flowability may be determined from the powder flow or by measurement of the angle of repose. The terms “acceptable flow and compression properties” imply the desired and thus preselected flow and compaction properties which must be met by the final liquisolid formulation. Depending on the excipient ratio (R) of the powder substrate an acceptable flowing and compressible liquisolid system can be obtained only if a maximum liquid load on the carrier material is not exceeded. This liquid/carrier ratio is termed liquid load factor Lf [w/w] and is defined as the weight ratio of the liquid formulation (W) and the carrier material (Q) in the

• Omit the process approaches like nanonisation, micronization techniques.

2.5.4 Disadvantages [16]

• Formulation of high dose lipophilic drugs the liquisolid tablet is one of the limitations of this technique.

• In order to achieve acceptable flowability and compactability for liquisolid powder formulation, high levels of carrier material and coating materials should be added. This will increase the weight of tablets to above one gram which makes them difficult to swallow. Consequently, it is impossible with conventional tablet methods to convert high dose to liquisolid tablets with a tablet weight of less than 50mg. Dissolution profile enhancement occurs in the presence of low levels of hydrophilic carrier, where coating material is not significant.

• High levels of carrier and coating materials are required to maintain acceptable flowability and compatibility for liquisolid powder formulation and that in turn will increases the weight of each tablet above 1 gm which is very difficult to swallow.

2.5.5 Mechanisms of Enhanced Drug Release from Liquisolid Systems [15]

• Increased Aqueous Solubility

• Increased Drug Surface