Chlorthalidone, also known as Hydrochlorthalidone, is a long-acting thiazide-like diuretic and antihypertensive active pharmaceutical ingredient. It promotes the excretion of sodium and chloride through the kidneys, increasing urinary water loss and reducing blood volume and blood pressure.
Chlorthalidone has the molecular formula C14H11ClN2O4S2 and a molecular weight of 338.83 g/mol. Its CAS Number is 77-36-1.
Chlorthalidone is a sulfonamide-containing benzophenone derivative with a prolonged duration of diuretic and antihypertensive activity. It is widely used in pharmaceutical formulations for the treatment of hypertension and fluid retention associated with selected conditions.
Unlike conventional thiazide diuretics, Chlorthalidone has a relatively long duration of action, making it suitable for once-daily antihypertensive therapy.
Chlorthalidone primarily inhibits the Na⁺/Cl⁻ cotransporter in the distal convoluted tubule of the nephron.
This decreases sodium and chloride reabsorption and increases urinary excretion of:
The resulting reduction in extracellular fluid volume and, with continued treatment, reduction in peripheral vascular resistance contributes to its antihypertensive effect.
Chlorthalidone API is used in the development and manufacture of:
Government pharmaceutical procurement documents in India list Chlorthalidone Tablets IP with “hydrochlorthalidone” as the associated name, including 6.25 mg and 25 mg tablet strengths.
Chlorthalidone is a synthetic pharmaceutical compound manufactured through controlled chemical synthesis, followed by purification, drying and quality-control testing.
Typical API testing includes identity, assay, related substances, water content, residue on ignition, residual solvents and elemental impurities according to the applicable pharmacopoeial or approved manufacturer specification.
Chlorthalidone is generally supplied as a white or almost white crystalline powder. It has low aqueous solubility and contains a sulfonamide functional group within its molecular structure.
Chlorthalidone should be stored in a tightly closed container, protected from excessive moisture, heat and direct light. Storage conditions should follow the manufacturer's current CoA, SDS and validated stability requirements.
Depending on the intended pharmaceutical application, documentation may include:
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Individual Impurity | NMT 0.5% |
| Water Content | NMT 1.0% |
| Melting Point | Approximately 238–240°C |
| Solubility | Practically insoluble in water; soluble in alcohol and dilute alkali solutions |