Pindolol API is a synthetic beta-adrenergic blocking agent belonging to the class of non-selective beta blockers. It is chemically identified as 1-(1H-indol-4-yloxy)-3-(isopropylamino)-2-propanol and is primarily associated with cardiovascular pharmaceutical applications. Pindolol acts as a non-selective beta-adrenergic antagonist and has also been described as having intrinsic sympathomimetic activity. The compound is identified by CAS Number 13523-86-9, with molecular formula C14H20N2O2 and molecular weight approximately 248.32 g/mol.
Pindolol has an established pharmaceutical history and has been used as an antihypertensive beta blocker. PubChem identifies it as a beta-adrenergic antagonist, vasodilator agent and antihypertensive drug. Its chemical structure contains an indole ring linked through an ether group to a substituted amino alcohol side chain.
Pindolol is generally described as a white to off-white crystalline powder. It is practically insoluble in water and has limited solubility in organic solvents. Pharmaceutical references identify Pindolol as a crystalline solid suitable for pharmaceutical analytical testing and formulation development.
The current USP 2025 monograph provides a clearly defined quality profile for Pindolol. USP specifies that Pindolol contains not less than 98.5% and not more than 101.0% of C14H20N2O2, calculated on the dried basis. Importantly, the current USP assay is performed using liquid chromatography, with UV detection at 219 nm, rather than a simple titrimetric assay.
The USP chromatographic assay uses an acetonitrile and sodium acetate mobile phase adjusted to pH 5.0. The chromatographic system uses an L10 column, a flow rate of 1 mL/min and UV detection at 219 nm. This makes the current USP assay particularly suitable for a CMS field labeled Assay (HPLC) or Assay (LC).
Pindolol is primarily associated with cardiovascular pharmacology. As a non-selective beta-adrenergic antagonist, it can reduce beta-adrenergic stimulation and has been used in the management of hypertension and certain cardiovascular conditions. PubChem also identifies its pharmacological roles as an antihypertensive and beta-adrenergic blocker.
Pindolol's pharmacological profile differs from that of some conventional beta blockers because it possesses intrinsic sympathomimetic activity. This characteristic has contributed to its historical clinical use and continuing pharmaceutical research interest.
For API manufacturers and pharmaceutical developers, Pindolol is relevant to the production and development of oral solid dosage forms and other pharmaceutical preparations containing the active ingredient. Accurate control of assay, related substances, moisture and inorganic residue is important for maintaining consistent API quality.
The USP 2025 Pindolol monograph provides several useful numerical specifications that can be directly incorporated into a pharmaceutical CMS. The assay requirement is 98.5–101.0% on the dried basis. Loss on drying is not more than 0.5%, determined at 105°C for four hours, while residue on ignition is not more than 0.1%.
USP also establishes specific chromatographic impurity limits. 4-Hydroxyindole is limited to NMT 0.15%, any individual unspecified impurity is limited to NMT 0.10%, and total impurities are limited to NMT 0.6%. The reporting threshold is 0.05%. These values are preferable for CMS specifications because they are supported by the current USP monograph rather than generic commercial specifications.
The USP assay and impurity procedures use liquid chromatography. For the assay, UV detection is at 219 nm; the organic impurity procedure uses UV detection at 264 nm. This distinction is important when documenting the analytical specifications because the impurity test and assay use different chromatographic conditions.
The current USP monograph specifies that Pindolol should be preserved in well-closed containers and protected from light. This storage information should be used in the CMS rather than assigning an unsupported numerical temperature unless a specific validated stability specification is available.
Pindolol is also included in the Japanese Pharmacopoeia, where loss on drying is specified at NMT 0.5% and residue on ignition at NMT 0.1%, providing additional pharmacopoeial support for these parameters.
Pindolol API has a well-established chemical identity and a current USP quality specification. For pharmaceutical manufacturing, the most important quality attributes include identity, assay, chromatographic purity, loss on drying and residue on ignition. The current USP requirements provide reliable numerical values for these parameters and should be preferred over unspecified commercial limits.
Pindolol is available as the free base and also has salt forms such as Pindolol Hydrochloride and Pindolol Maleate. These should not be treated as interchangeable API forms because they have different molecular formulas, molecular weights and CAS numbers. The free-base Pindolol covered on this page is CAS 13523-86-9, with molecular weight 248.32 g/mol.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.6% |
| Water Content | NMT 0.5% |