Liquid salts for effective and safe topical use

Formulating drugs as liquid salts may provide a safe and efficient strategy for topical delivery of drugs that cause skin toxicity, say researchers, including one of Indian-origin. A novel formulation of the drug propranolol as a liquid salt enables delivery through skin with reduced toxicity, the findings showed.

"Propranolol is positively charged which is a likely source of its toxicity. Shielding of this charge by association with a counter species in the liquid salt reduces its toxicity. These findings are broadly applicable to many charged drugs" said study senior author Samir Mitragotri, professor at University of California, Santa Barbara in the US.

Skin toxicity remains a major challenge in the design and use of new topical drug formulations. Many drugs must be dissolved in organic solvents which are typically toxic to the skin.

Many drugs such as propranolol itself show dose-dependent skin toxicity. Formulating drugs as liquid salt mitigates both sources of toxicity.

Given their fluid nature, liquid salts eliminate the necessity of organic solvents. In addition, counter ions used to form the liquid salts shield the drug charge, which further reduces drug-induced toxicity.

The researchers said that this is the first study that reports the design of liquid salts to minimise skin toxicity. Such formulations can increase the spectrum of drugs that can be safely delivered via a transdermal patch.

"This technology presents an exciting new, patient compliant solution for treating diseases," study co-author Michael Zakrewsky from University of California, Santa Barbara. (The study appeared in the journal TECHNOLOGY.)