The invention relates to a pharmaceutically acceptable acid addition salt of: (i) S-pindolol; and (ii) an organic acid, wherein the organic acid has: a pKal of greater than or equal to 2.5; and a chemical formula of CxHy(CO2H)z, where x is from 1 to 10, y is from 2 to 20 and z is 1 or 2. The pharmaceutically acceptable acid addition salt is useful in treating conditions such as cachexia, sarcopenia, a neuromuscular disorder and muscle weakness.