Clemastine, also known as meclastin, is a first-generation H1 histamine antagonist (antihistamine) with anticholinergic properties (drying) and sedative side effects. Like all first-generation antihistamines, it is sedating. Technically, clemastine acts as an H1 receptor inverse agonist with additional antagonism at muscarinic receptors, which contributes to its drying and antimuscarinic adverse effects; the fumarate salt is commonly used for oral formulation because it improves stability and manufacturability. The molecule is lipophilic and crosses the blood brain barrier, explaining central nervous system effects such as drowsiness and impairment of psychomotor performance. In pharmaceutical practice clemastine is formulated in tablets and syrups, analyzed and released using chromatographic assays such as HPLC with UV detection and characterized by mass spectrometry and NMR for identity and purity. Clinical and formulation considerations include dose adjustment or avoidance in the elderly and in patients with prostatic hypertrophy, glaucoma, or other conditions sensitive to anticholinergic activity, and monitoring for additive central nervous system depression when combined with alcohol or sedative agents.
Parent: Clemastine
Parent: Clemastine
Parent: Clemastine Fumarate / Clemastine
Parent: Clemastine
Parent: Clemastine
Typical API control strategies define acceptance criteria for related compounds and impurities and use stability and forced-degradation studies to identify degradants; common related compounds and impurities reported in synthesis and degradation pathways include N-desmethyl clemastine, clemastine N-oxide, positional isomers and stereoisomers, oxidative and hydrolytic breakdown products, and residual starting materials or solvents. Typical analytical specifications used in many monographs and manufacturer dossiers set individual unidentified impurities at not more than 0.1 to 0.5 percent by area and total impurities at not more than about 1.0 percent by area, with tighter limits applied to specified genotoxic or reactive species; limits and testing methods are established based on route of synthesis, known degradants, and regulatory guidance. Impurity and related compound profiling is routinely performed by HPLC with orthogonal confirmation by LC-MS and NMR, while residual solvent levels are measured by GC or headspace GC and elemental impurities are controlled according to appropriate pharmacopoeial thresholds.
Clemastine is used to relieve symptoms of allergic conditions such as allergic rhinitis, urticaria, and pruritus; it is also used for symptomatic relief of runny nose and sneezing associated with common colds and sometimes for night-time allergy relief because of its sedating properties.
Celestamine is a combination product typically containing a corticosteroid and an antihistamine and is used to treat more severe allergic and inflammatory conditions such as acute dermatitis, severe allergic reactions, and certain forms of drug eruption where both anti-inflammatory and antihistaminic actions are needed; product composition and indications vary by market so refer to the local label.
No, loratadine is a second-generation H1 antihistamine with minimal central nervous system penetration and is generally non-sedating, whereas clemastine is a first-generation antihistamine that crosses the blood brain barrier and commonly causes sedation and anticholinergic effects.
Another name for clemastine is meclastin; the drug is also commonly encountered as clemastine fumarate and marketed under various brand names such as Tavist in some regions.
