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Expected pharmacological effect
Causality assessment · Expected pharmacological effect
Tizanidine and Hypotension: is the FAERS signal real?
A written Bradford Hill assessment of one drug–event pair. The grade is a judgement about the signal, not a statement that this drug causes this event in any one person; FAERS counts are reports, not rates.
Tizanidine ↔ Hypotension
n=509 co-reports · PRR 2.2 · ROR 2.3
Tizanidine is a centrally acting alpha-2 agonist that reduces spasticity but also lowers blood pressure and heart rate; hypotension and orthostatic intolerance are labelled effects (509 co-reports, PRR 2.2), amplified by CYP1A2 inhibitors such as ciprofloxacin, which raise tizanidine levels and have caused profound hypotension.
Regulatory basis: tizanidine prescribing information — hypotension/bradycardia; contraindicated with ciprofloxacin and other CYP1A2 inhibitors.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Blood-pressure fall with dosing |
| Strength | met | PRR 2.2, modest |
| Consistency | met | Seen across trials and series |
| Specificity | partial | Shared with clonidine |
| Biological gradient | met | Dose-related |
| Plausibility | met | Alpha-2 agonism reducing sympathetic tone |
| Coherence | met | Fits the pharmacology |
| Experiment | met | Trials measured blood-pressure change |
| Analogy | met | Analogous to clonidine hypotension |
This table is this page's own qualitative read of the literature cited above, not an automated or citation-gated assessment — see the note at the bottom of this page.
✗ No ClinicalTrials.gov results-posting trial in the top search hits for tizanidine captured hypotension as a tracked adverse event in a usable structure. Spasticity trials measured blood pressure as a vital-sign safety parameter rather than reporting hypotension as a coded event.