Hydralazine is a synthetic antihypertensive active pharmaceutical ingredient belonging to the phthalazine derivative class. It is a direct-acting vasodilator that primarily relaxes arteriolar smooth muscle, resulting in reduced peripheral vascular resistance and lowering of blood pressure.
Hydralazine has the molecular formula C₈H₈N₄ and a molecular weight of 160.18 g/mol. Its CAS Number is 86-54-4.
Hydralazine is an established cardiovascular pharmaceutical compound used in the management of hypertension. It is also used in specific clinical situations such as severe hypertension and, in combination with other medicines, certain heart-failure treatment regimens.
Hydralazine is commonly encountered as hydralazine hydrochloride in pharmaceutical formulations. The free base and hydrochloride salt should be treated as separate materials in an API database.
Hydralazine acts predominantly on arteriolar smooth muscle, producing direct vasodilation.
The resulting decrease in systemic vascular resistance reduces arterial blood pressure. Because hydralazine primarily dilates arterioles rather than veins, its hemodynamic effects can be accompanied by reflex sympathetic activation.
Hydralazine API is used in the development and manufacture of:
Hydralazine is a synthetic pharmaceutical compound manufactured through controlled chemical synthesis followed by purification, drying and quality-control testing.
Typical quality assessment may include identity, assay, related substances, water content, residue on ignition, residual solvents and elemental impurities according to the applicable pharmacopoeial or approved manufacturer specification.
Hydralazine is generally described as a white to almost white crystalline powder. It is a weakly basic nitrogen-containing heterocyclic compound and has limited solubility in water as the free base. The hydrochloride salt has substantially improved aqueous solubility.
Hydralazine should be stored in a tightly closed container, protected from excessive moisture, heat and direct light. Follow the manufacturer's current CoA, SDS and validated stability requirements.
Depending on grade and intended pharmaceutical application, documentation may include:
| Parameter | Specification |
|---|---|
| Appearance | White to off-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% |
| Total Impurities | NMT 2.0% |
| Water Content | NMT 1.0% |
| Melting Point | 172–174°C |
| Solubility | Slightly soluble in water; soluble in dilute mineral acids |