Poly(amidoamine) Dendrimers as a Pharmaceutical Excipient. Are We There yet?

Drug solubility could affect the therapeutic use of a drug because the biological activity of a drug is only possible if some fraction of a dissolved drug can permeate and overcome biological membranes to reach its site of action. The solubility-permeation interplay is therefore, probably the most important factor in determining a successful therapeutic outcome of any drug because more than 40% of marketed drugs and more than 70% of pipeline drugs show poor water solubility. Several solubilization techniques are used and include, balancing of pH-pK_a properties, employment of cosolvents, and the solubilization by host-guest carriers. A relatively new addition to the polymer plethora of solubilizers are the poly(amidoamine) dendrimers. These highly branched, "tree-like" nanocarriers have a significant solubilization capacity for drugs in their cavities and also potentially via their terminals. Despite their successful solubilization capability, they are still plagued by some undesired properties such as cytotoxicity. Poly(amidoamine) however, seems to be a very lucrative target to develop into a pharmaceutical excipient, which will ultimately be confirmed by an official pharmacopeial monograph.