Handbook of Solvents - George Wypych - ChemTech - Ventech!

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This discussion is intended to provide an easy approach for predicting the effect of
cosolvents, which are frequently involved in pharmaceutical and environmental applications,
on the solubility of organic chemicals. The starting point is the widely used log-linear
model.
14.21.2.2 Applications of cosolvency in pharmaceutical sciences and
industry
Although many drugs are formulated and administrated in solid, vapor, powder, or other
forms, using solutions as drug delivery vehicle has significant advantages. Most
parenterally administered medicines are in the form of liquid solution, and for intravenous
injection, liquid form dosage is the only possible form. However, drugs are usually designed
with little concern about their level of solubility in solution. It is the task of pharmaceutical
formulators to find appropriate forms for the drug to be effectively delivered into
biological systems.
The phenomena of cosolvency have been studied for more than a century by pharmaceutical
scientists. Numerous experimental data are published in the literature, and most of
the models mentioned in the introduction section have been developed from pharmaceutical
research. In addition to the need of solubilizing drugs which are poorly water-soluble, controlling
the dissolution of drugs administered as solids to optimize therapeutic activity also
demands an improved understanding of drug solubilization. Approaches that may be pursued
to enhance drug solubility in a liquid dosage formulation include adjusting pH, adding
surfactants, cosolvents, or complexation agents. Choice of these techniques depends primarily
on the drug’s chemical structure and physicochemical properties. For example, control
of pH is applicable only when the drug is an electrolyte. To solubilize nonelectrolyte
drugs, the use of cosolvents outweighs surfactants and complexing agents. 20
Cosolvents that are routinely used in drug formulation include ethanol, propylene glycol,
polyethylene glycol, and glycerin. Examples of pharmaceutical products containing
these cosolvents are summarized in Table 14.21.2.1.
Table 14.21.2.1. Selected pharmaceutical products containing cosolvents
Trade Name Cosolvent vol% Manufacturer Type
Aclovate cream Propylene glycol Schering Topical
Alurate elixir Ethanol 20 Roche Oral liquid
Amidate Propylene glycol 35 Abbott Parenteral
Amphojel Glycerin Wyeth-Ayerst Oral
Apresoline Propylene glycol 10 Ciba Parenteral
Aristocort cream Propylene glycol Fujisawa Topical
Ativan
Polyethylene glycol
Propylene glycol
20
80
Wyeth-Ayerst Parenteral
Bentyl syrup Propylene glycol Lakeside Oral
Brevibioc Ethanol 25 DuPont Parenteral
Cleocin T lotion Glycerin Upjohn Topical