Tizanidine Hydrochloride

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Cat Number

API0231623

CAS Number

64461-82-1

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Product Detail Description Scientific Support Customer Q&A

CAS Number

64461-82-1

EINECS

630-412-1

Storage

Store at room temperature

Synonyms

Tizanidine Hcl; DS 103-282; AN021; DS-103-282; B53E3NMY5C; Tizanidine (as hydrochloride); ONTRALFY

Molecular Formula

C9H9Cl2N5S

Molecular Weight

290.17

Smiles

C1CN=C(N1)NC2=C(C=CC3=NSN=C32)Cl.Cl

Appearance

White to off-white fine crystalline powder

Melting Point

280℃

General Description

Tizanidine hydrochloride is a centrally acting alpha-2 adrenergic agonist used as a short-acting muscle relaxant for spasticity management. The drug is chemically an imidazole derivative unrelated to other muscle relaxants.

Mechanism of Action

Tizanidine selectively stimulates alpha-2 adrenergic receptors in the spinal cord and brainstem, reducing the release of excitatory amino acids (glutamate and aspartate) from presynaptic interneurons. This inhibition suppresses polysynaptic reflex arcs that mediate spasticity and muscle hypertonia. The effect is dose-dependent and reversible. Unlike baclofen, tizanidine also reduces substance P release, contributing to analgesia.

Application

Tizanidine is indicated for the management of spasticity associated with multiple sclerosis, spinal cord injury, cerebral palsy, and stroke. It is also used off-label for chronic tension-type headaches and myofascial pain syndromes.

Analysis of global pharmacovigilance data (WHO database) identified 91 reports of tizanidine‑ciprofloxacin coadministration despite a formal contraindication. Most patients were female (64.8%), median age 54 years. Reported adverse drug reactions predominantly affected the nervous and cardiovascular systems, including fatal outcomes in two cases. The most frequent reactions were central nervous system depression and cardiac effects. The authors stress that concomitant use should be absolutely avoided given the severe and potentially fatal risks.

Fig. 1 Reporting countries and primary source. (Rudolph A, et al., 2021)

References

Rudolph A, et al. Coadministration of tizanidine and ciprofloxacin: a retrospective analysis of the WHO pharmacovigilance database. Eur J Clin Pharmacol. 2021;77(6):895-902.

Does Tizanidine Hydrochloride require protection from light during storage?

Yes, it is photosensitive. Light exposure can cause discoloration and degradation of the imidazoline ring. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Tizanidine Hydrochloride?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can accelerate hydrolysis of the amide bond.

Is Tizanidine Hydrochloride hygroscopic, and how is this managed?

It is moderately hygroscopic. Storage in tightly sealed containers with desiccant is recommended to prevent caking and potential hydrolysis.

How is the impurity 2-amino-5-chlorobenzothiazole monitored during stability?

This potential degradation product is quantified using a stability-indicating HPLC method with UV detection, ensuring it remains below ICH qualification thresholds.