Chemical Identity and Pharmacological Profile

Orphenadrine hydrochloride (CAS 341-69-5) is the hydrochloride salt of orphenadrine, a diphenyl ether-based tertiary amine. Its molecular formula is C₁₈H₂₃NO·HCl with a molecular weight of approximately 305.84 g/mol. The compound presents as a white to off-white crystalline powder that is freely soluble in water and ethanol, making it readily amenable to aqueous and organic solution preparation in laboratory settings.

Pharmacologically, orphenadrine acts primarily as a muscarinic acetylcholine receptor antagonist (anticholinergic). Research has further identified activity at NMDA (N-methyl-D-aspartate) glutamate receptors, histamine H₁ receptors, and sodium channels, positioning it as a multi-target pharmacological tool compound. Its structural analogy to diphenhydramine underlies shared antihistaminergic properties. These diverse receptor interactions make orphenadrine hydrochloride a valuable reagent for mechanistic studies in neuropharmacology and muscle physiology.

Safe Handling, Storage, and Stability

As with all research reagents, orphenadrine hydrochloride should be handled using standard laboratory safety practices. Personnel should wear appropriate personal protective equipment (PPE) including nitrile gloves, a laboratory coat, and safety glasses. Avoid inhalation of dust or aerosols. Work in a well-ventilated area or under a fume hood when weighing powders.

The compound should be stored in a tightly sealed container away from light, heat, and moisture. Recommended storage conditions are at room temperature (15–25 °C) in a cool, dry location, although refrigeration (2–8 °C) may further extend shelf life. Ensure the container is properly labelled and stored separately from oxidising agents and strong acids or bases.

Orphenadrine hydrochloride is considered stable under recommended storage conditions. Prepared stock solutions in water or DMSO should be aliquoted and stored at −20 °C to minimise freeze-thaw degradation. Avoid repeated freeze-thaw cycles. Always consult the product-specific Safety Data Sheet (SDS) before use.

Note: Specific stability half-life data for prepared solutions are not provided in the source material and should be verified against the product SDS or primary literature.

Solution Preparation and Reconstitution Protocol

Orphenadrine hydrochloride is freely soluble in water and ethanol, and is also soluble in DMSO, making it versatile for a range of assay formats. The following general protocol is recommended for stock solution preparation:

1. Determine target concentration: Calculate the mass of orphenadrine hydrochloride required for your desired stock concentration (e.g., 10 mM or 100 mM) using the molecular weight of 305.84 g/mol.
2. Weigh accurately: Tare a clean microcentrifuge tube or vial and weigh the required mass of compound using an analytical balance. Equilibrate the vial to room temperature before opening to prevent moisture condensation.
3. Add solvent: For aqueous stocks, add the appropriate volume of sterile water, PBS, or physiological saline. Vortex gently until completely dissolved. For DMSO stocks, add anhydrous DMSO and vortex to dissolve.
4. Filter if required: For cell-based assays, filter-sterilise the solution through a 0.22 µm membrane filter.
5. Aliquot and store: Divide into single-use aliquots and store at −20 °C. Label with compound name, concentration, solvent, date, and preparer's initials.

When diluting DMSO stocks into aqueous assay media, ensure the final DMSO concentration does not exceed 0.1–0.5% to avoid solvent toxicity artefacts in biological assays.

Research Applications

Orphenadrine hydrochloride serves as a valuable pharmacological tool compound across several research domains:

• Neuropharmacology: Used to characterise muscarinic receptor subtypes and to investigate anticholinergic mechanisms in central and peripheral nervous system models. Its NMDA receptor antagonism is studied in the context of neuroprotection, pain signalling, and models of neurological disorders.
• Skeletal muscle physiology: Employed as a reference agent in studies of centrally-acting muscle relaxation, aiding elucidation of spinal cord reflex pathways.
• Analytical chemistry and quality control: Functions as a certified reference standard for HPLC, LC-MS/MS, and other chromatographic methods used in pharmaceutical analysis and pharmacokinetic studies.
• In vitro receptor binding assays: Used in competitive binding studies to displace radiolabelled ligands from muscarinic or histamine receptors.
• Drug interaction and transporter studies: Investigated for interactions with cytochrome P450 enzymes and drug transporters relevant to metabolic liability assessment.

Researchers should validate assay-specific concentrations empirically and consult the primary literature for guidance on relevant experimental parameters.

Quality, Specification, and Ordering Information

Aladdin Scientific supplies orphenadrine hydrochloride under SKU O423488. Researchers are advised to review the full product specification sheet, including purity (%), analytical method (e.g., HPLC), and lot-specific Certificate of Analysis (CoA), prior to use in critical experiments.

For enquiries regarding bulk quantities, custom specifications, or alternative formats, contact Aladdin Scientific's technical sales team. Ensure that your procurement documentation references SKU O423488 to avoid confusion with structurally related analogues.

Reference product: O136159 (as noted in product description). Researchers should confirm whether O136159 and O423488 differ in grade, purity, or packaging before substitution.

All products are intended for research use only (RUO) and are not suitable for diagnostic, therapeutic, or human consumption purposes without further validation and regulatory approval.