What HCl Stands For in Metformin
HCl stands for hydrochloride, which is the salt form of metformin used in pharmaceutical formulations.
Chemical Nomenclature
The chemical name of metformin hydrochloride is N,N-dimethylimidodicarbonimidic diamide hydrochloride, with a molecular formula of C₄H₁₁N₅ • HCl and molecular weight of 165.63 1
Metformin hydrochloride is a white to off-white crystalline compound that is freely soluble in water, slightly soluble in alcohol, and practically insoluble in acetone and methylene chloride 1
Pharmaceutical Significance
The hydrochloride salt form is used because it provides optimal solubility and stability characteristics for oral tablet formulations 1
The pKa of metformin is 12.4, and a 1% aqueous solution of metformin hydrochloride has a pH of 6.68 1
Metformin hydrochloride tablets are available in 500 mg, 850 mg, or 1000 mg strengths, with each tablet containing the specified amount of metformin hydrochloride (not just the base metformin) 1
Clinical Context
Metformin hydrochloride is classified as a biguanide antihyperglycemic agent and remains the first-line therapy for type 2 diabetes in adults 2, 3
The hydrochloride salt form does not alter the drug's mechanism of action, which primarily involves suppression of hepatic glucose production (particularly gluconeogenesis) 4