Oral liquids solubilisates

The properties of the active substance dominate and often restrict the choice of the type of oral liquid. Oral liquids are classified according to their physical properties as solutions, suspensions, emulsions and solubilisates. Solutions and suspensions are treated in depth because they are most often dealt with in daily practice. 

Solutions Suspensions Emulsions Solubilisates Oral liquids Syrup Flavour Acceptable daily intake Colour Taste Feeding mbe Preparation Formulation... 

Different oral liquid dosage forms offer the possibility to adjust the dosage form optimally to the requirements. The options are solutions, suspensions, emulsions or solubilisates. The flow scheme in Fig. 5.1 shows a route to the oral liquid form that is to be preferred due to the qualities of the active substance, particularly solubility, stability and taste. The required concentration influences the choice as well. 

The main choice will be between an oral solution and an oral suspension. For some active substances an emulsion or solubilisate is the appropriate form. However in some cases (e.g. because of an intermediate solubility of the active substance) the pharmacist will have no other option than to dispense an oral solid dosage form and instruct the patient how to manipulate it safely (see Sect. 37.6.2). Proper consideration of the options may prevent formulation mistakes with probably severe consequences. This especially applies to the unreflected use of suspending bases for rendering an oral solid into an oral liquid. 

Water supports the growth of micro-organisms, therefore oral aqueous solutions, suspensions, emulsions and solubilisates in multidose containers should be preserved. Preservatives may be used for that purpose as well as excipients with preservative properties, such as propylene glycol. See Sect. 23.8 for extensive information on preservatives. Table 5.18 summarises preservatives with properties especially relevant for oral liquids. 

Syrups are a very commonly used form of sugars. They contain approximately 45-65 % of sugar, water and a preservative. Sometimes a flavouring is added. The preservative is most often methyl parahydroxybenzoate 0.1-0.15 %. Syrups can be very useful for improving the taste of oral liquid preparations and sometimes they can be used to stabilise a solubilisate of oil and polysorbate, e.g. in a vitamin A micellar solution (Table 23.12). 

Solubilisates for oral use colloidal solutions of a liquid active substance in an inuniscible liquid this term is not on the list of EDQM standard terms. 

In pharmacy preparations several different types of disperse systems are found. Liquid dispersions are dispersions in which a solid substance is dispersed into a liquid substance, such as suspensions for cutaneous applications and oral suspensions, and dispersimis in which a liquid is dispersed in a non-miscible liquid, such as emulsions and solubilisations. 

The dispersion of a liquid into another liquid with which it is immiscible to obtain a sufficiently physically stable product is only possible by emulsifying or solubilising, using surface-active substances (tensides, surfactants). This process is applied in the preparation of creams and solubilisations. In oral emulsions surface-active substances are not used, but instead viscosity enhancers that possess little surface activity. Below the preparation of emulsirMis and solubilisations is briefly discussed. 

---