Tizanidine is a biologically active compound with diverse pharmacokinetic and pharmacodynamic properties. It has a partition coefficient (LogD6.5) of -0.68 and a delta logD of -0.81 between pH 6.5 and 7.4. The compound’s ionization constant (pKa) is 8.0, reflecting its ionization behavior. It demonstrates moderate oral bioavailability in humans at 49%, alongside high solubility at pH 7.4 (600 μM) and pH 7.2 (18,250 μg/mL).
In terms of distribution and clearance, Tizanidine has a volume of distribution at steady state (Vdss) of 2.4 L/kg and high binding to plasma proteins with a fraction unbound (Fu) of 0.7. It shows a total body clearance of 11.0 mL/min/kg and a renal clearance of 0.33 mL/min/kg, indicating significant renal excretion and suggesting efficient clearance from the body. The hepatic clearance is low at 10.7 mL/min/kg.
Tizanidine displays bioactivity at several targets. It displaces [125I]PIC from human alpha2 adrenoceptors and human imidazoline receptor 1, with Ki values of 117.9 nM and 28.31 nM respectively, and a selectivity ratio of 0.6197 favoring imidazoline receptor 1. It also inhibits human FAAH at 1 μM concentration, demonstrating 7.43% inhibition. Additionally, it inhibits a range of enzymes and receptors, including moderate inhibition of SARS-CoV-2 3CL-Pro protease and binding activities towards various adrenergic and histamine receptors.
Pharmacodynamically, Tizanidine shows efficacy as an agonist at alpha-2A and alpha-2C adrenergic receptors, inhibiting forskolin-stimulated cAMP accumulation with an EC50 of 86.0 nM for alpha-2A. It presents antiviral activity against SARS-CoV-2 and demonstrated moderate inhibition of induced cytotoxicity in VERO-6 cells at a concentration of 10 μM.
However, Tizanidine is also associated with significant hepatotoxic effects, as evidenced by elevated liver enzymes such as ALT, AST, and others. It can induce conditions like cholelithiasis, cirrhosis, hepatic failure, and hepatitis, suggesting a need for caution in its therapeutic use.
Overall, Tizanidine represents a multi-faceted pharmaceutical agent with notable pharmacological actions and potential bioactivities against various biological targets, but caution is warranted due to its association with liver toxicity..
Note: Summary generated by AI. Data source: ChEMBL 