Salt forms and counter-ions template

Hydrochloride, mesylate, besylate, maleate, tosylate and sodium — the counter-ions most used to make drug salts, drawn as structures, with a reference table of which salt suits a basic or acidic drug and an example marketed salt.

What the template shows

• The common pharmaceutical salts, their counter-ions and an example drug for each
• Common counter-ions
• Chloride (HCl salt)
• Salt form, counter-ion and an example
• Salt form Counter-ion For a… Example drug Hydrochloride Cl⁻ basic drug fluoxetine HCl Mesylate CH₃SO₃⁻ basic drug imatinib mesylate Besylate C₆H₅SO₃⁻ basic drug amlodipine besylate Maleate ⁻OOC–CH=CH–COOH basic drug enalapril maleate Tosylate 4-CH₃C₆H₄SO₃⁻ basic drug sorafenib tosylate Sodium Na⁺ acidic drug diclofenac sodium
• Most small-molecule drugs are marketed as salts: a salt can improve solubility, dissolution, stability and crystallinity without changing the active molecule.
• A basic drug (amine) pairs with an acid counter-ion (HCl, mesylate, besylate, maleate, tosylate); an acidic drug (carboxylic acid) pairs with a base (sodium, potassium, calcium).
• The counter-ion is chosen for pKa (a ≈ 2–3 unit gap ensures proton transfer), safety, solubility and solid-form properties.
• The free form and the salt are the same drug; the dose is usually stated as the free-base (or free-acid) equivalent.
• Berge, Bighley & Monkhouse, J. Pharm. Sci. 1977, 66, 1 · every part of this sheet is editable

Drawn with 36 atoms, 3 shapes – every one editable in MolDraw.

Sources

• Berge, Bighley & Monkhouse, J. Pharm. Sci. 1977, 66, 1 Review