Tizanidine
Tizanidine. Centrally-acting α2-adrenergic agonist — reduces presynaptic excitatory neurotransmitter release in spinal cord interneurons → less… Oral half-life 3 h.
Centrally-acting α2-adrenergic agonist — reduces presynaptic excitatory neurotransmitter release in spinal cord interneurons → less muscle tone. Used for spasticity. CYP1A2 substrate — ciprofloxacin / fluvoxamine + tizanidine = severe hypotension (boxed warning).
PK: its citation is a FOOD-EFFECT and formulation-comparison study reporting no half-life, no volume, no bioavailability and no rate — zero-content on all four. A SCALAR BIOAVAILABILITY IS INDEFENSIBLE: fluvoxamine raises exposure 33-FOLD, with a range of 14 to 103-fold within ten healthy people; oral contraceptives about fourfold; food about 1.45-fold. The measured 21% is stored with that CYP1A2-conditional caveat. V 175 L is dropped without replacement — it is a placeholder SHARED WITH SELEGILINE, and the best available source explicitly warns that any oral-derived tizanidine volume is "almost certainly overestimates", while no intravenous study exists. A genuine published absorption rate with a 0.36 h lag replaces the unsourced one, from a study in the indicated spasticity population rather than healthy volunteers, which is recorded. UNIQUELY IN ITS GROUP THE EFFECT IS COUPLED — relief "appeared greatest at the time of peak plasma levels" — so if anything the stored equilibration is too slow rather than too fast.
Pharmacokinetics
- Oral — t½ 3 h · F 21% · ka 2.31 h⁻¹
Sources: PMID:17062304, PMID:36101495, PMID:3447935, PMID:6617726, PMID:15060511