Many drug molecules are combined with a counter-ion to create a salt that is more stable, easier to manufacture, or better suited to a particular dosage form. Hydrochloride and pamoate are two such counter-ions.
The therapeutic molecule is the same; the salt affects properties such as solubility and the molecular weight, which is why labeled strengths of two salts of the same drug are not always interchangeable numbers. A pharmacist can translate between them for a specific prescription.