SAFINAMIDE MESYLATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SAFINAMIDE MESYLATE (SAFINAMIDE MESYLATE).
Selective and reversible monoamine oxidase B (MAO-B) inhibitor. Increases dopamine levels in the striatum by inhibiting its metabolism. Also blocks voltage-dependent sodium and calcium channels, modulating neurotransmitter release.
| Metabolism | Primarily metabolized by amidase hydrolysis to inactive metabolites (safinamide acid and O-demethylated safinamide acid). Minor contributions from CYP3A4 (N-dealkylation). No significant CYP enzyme inhibition or induction. |
| Excretion | Primarily hepatic metabolism (approx. 90% via amide hydrolysis and oxidation, mainly CYP3A4), followed by renal excretion of metabolites. Less than 7% of the dose is excreted unchanged in urine. Biliary/fecal excretion accounts for roughly 50% of the administered dose, with the remainder eliminated via renal excretion of metabolites. |
| Half-life | Terminal elimination half-life is approximately 20–26 hours (mean ~22 hours), allowing once-daily dosing. Steady-state is achieved within 3–5 days. |
| Protein binding | Approximately 88–95% bound to plasma proteins, primarily to albumin and to a lesser extent alpha-1-acid glycoprotein. |
| Volume of Distribution | Apparent volume of distribution (Vd/F) is approximately 2.1 L/kg, indicating extensive distribution into tissues beyond plasma volume. |
| Bioavailability | Absolute oral bioavailability is approximately 95%, with minimal first-pass metabolism. Food does not significantly affect bioavailability, but high-fat meals may delay absorption (Tmax increased by ~1 hour). |
| Onset of Action | Oral administration: clinical effects on motor symptoms (e.g., reduction in OFF time) are typically observed within 2 weeks of starting therapy at therapeutic doses (50–100 mg once daily). |
| Duration of Action | 24 hours due to once-daily dosing regimen. The drug provides sustained inhibition of monoamine oxidase B throughout the dosing interval. |
50 mg orally once daily; may increase to 100 mg orally once daily after 2 weeks based on tolerability and efficacy.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-49 mL/min: 50 mg orally once daily; CrCl <30 mL/min: not recommended (no data). |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: 50 mg orally once daily; Child-Pugh Class C: not recommended. |
| Pediatric use | Safety and efficacy not established; no recommended dose. |
| Geriatric use | No specific dose adjustment; monitor for increased adverse effects (e.g., dyskinesia, hallucinations) due to age-related decline in renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SAFINAMIDE MESYLATE (SAFINAMIDE MESYLATE).
| Breastfeeding | No data on presence in human milk. Safinamide and its metabolites are excreted in rat milk. M/P ratio unknown. Due to potential for serious adverse reactions (e.g., serotonin syndrome, monoamine oxidase inhibition), breastfeeding is not recommended during therapy. |
| Teratogenic Risk | FDA Pregnancy Category C. Animal studies (rats and rabbits) showed no teratogenicity at clinically relevant doses, but fetal toxicity (decreased fetal weight, delayed ossification) occurred at maternal toxic doses. No adequate human studies. Risk cannot be ruled out. Avoid in first trimester if possible; use only if benefit outweighs risk. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Concomitant use with other MAOIs (including linezolid and intravenous methylene blue)","Concomitant use with pethidine (meperidine) and other opioid analgesics known to interact with MAOIs","Concomitant use with serotonergic drugs (SSRIs, SNRIs, TCAs, triazolopyridines, serotonergic antiemetics, St. John's wort)","Severe hepatic impairment (Child-Pugh class C)","Pheochromocytoma","History of hypersensitivity to safinamide or any product component"]
| Precautions | ["May cause hypertensive crisis if used with other MAOIs or sympathomimetics","May cause serotonin syndrome if used with serotonergic drugs (e.g., SSRIs, SNRIs)","May cause retinal toxicity (monitor for visual changes)","May cause dopamine dysregulation syndrome (impulse control disorders)","Concomitant use with opioids (especially meperidine) is contraindicated","Hypertensive crisis with tyramine-rich foods: although low risk at therapeutic doses, patients should avoid high doses of tyramine"] |
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| Fetal Monitoring | Monitor for hypertension, serotonin syndrome (coadministration with other serotonergic drugs), and hepatic function (transaminases monthly for first 6 months). Assess fetal growth and well-being if used during pregnancy. |
| Fertility Effects | Animal studies (rats) showed no impairment of male or female fertility at exposures up to 6 times the maximum recommended human dose. No human data on fertility effects. |