RELPAX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RELPAX (RELPAX).
Selective 5-HT1B/1D receptor agonist; causes vasoconstriction of intracranial arteries, inhibits trigeminal nerve activation, and reduces neurogenic inflammation.
| Metabolism | Primarily metabolized by CYP3A4; less than 10% excreted unchanged in urine. |
| Excretion | Approximately 60% of the dose is excreted in urine (primarily as metabolites, with ~14% unchanged) and 40% in feces via biliary elimination. |
| Half-life | Terminal elimination half-life is 6.2 hours (range 4.7–8.1 hours) in healthy adults; prolonged in renal impairment (up to 9.5 hours). |
| Protein binding | Approximately 30% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Vd is 3.0 L/kg (range 2.1–4.0 L/kg), indicating extensive tissue distribution (extravascular). |
| Bioavailability | Oral bioavailability is 50% (range 40–60%) due to first-pass metabolism; no other routes available. |
| Onset of Action | Oral: headache relief (reduction from moderate/severe to mild/none) begins within 30 minutes; peak plasma concentration at 1.5–2 hours. |
| Duration of Action | Clinical effect duration is approximately 24 hours, based on sustained pain relief and low headache recurrence rate within 24 hours post-dose. |
20-40 mg orally once; maximum 80 mg per 24 hours. Single dose may be repeated after 2 hours if migraine recurs.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl 30-80 mL/min). Contraindicated in severe renal impairment (CrCl <30 mL/min). |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh C). No dose adjustment for mild to moderate (Child-Pugh A/B). |
| Pediatric use | Not recommended for patients <18 years of age; safety and efficacy not established. |
| Geriatric use | Use with caution. No specific dose adjustment, but increased sensitivity; start at 20 mg. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for RELPAX (RELPAX).
| Breastfeeding | Eletriptan is excreted into human breast milk. The milk-to-plasma ratio is approximately 0.14 for the parent drug and 0.33 for the active metabolite. Concentration in milk is low (mean relative infant dose approximately 0.02% of maternal weight-adjusted dose). Caution is advised, particularly in infants with impaired renal function. Monitor infant for potential adverse effects such as drowsiness or feeding difficulties. |
| Teratogenic Risk | Pregnancy Category C. Eletriptan (RELPAX) has shown embryotoxicity and fetotoxicity in animal studies at maternally toxic doses. There are no adequate and well-controlled studies in pregnant women. Use only if potential benefit justifies potential risk to the fetus. First trimester: limited data suggest no major malformations; however, definitive conclusions cannot be drawn. Second and third trimesters: risk unknown; avoid use due to potential uteroplacental vasoconstriction and decreased uterine blood flow. |
■ FDA Black Box Warning
Do not administer to patients with ischemic heart disease, coronary artery vasospasm (including Prinzmetal variant angina), or other significant underlying cardiovascular disease.
| Serious Effects |
["Ischemic heart disease, history of myocardial infarction, coronary artery vasospasm","Cerebrovascular disease (e.g., stroke, transient ischemic attack)","Uncontrolled hypertension (≥180/110 mmHg)","Hemiplegic or basilar migraine","Concurrent use of ergotamine derivatives or other 5-HT1 agonists","Concurrent MAO inhibitor use or within 2 weeks of discontinuation","Severe hepatic impairment (Child-Pugh C)","Hypersensitivity to eletriptan or any component of the formulation","Prophylactic use for migraine"]
| Precautions | ["Risk of myocardial ischemia, infarction, and coronary vasospasm","Cerebrovascular events (e.g., stroke, cerebral hemorrhage)","Serotonin syndrome (especially with SSRIs, SNRIs, MAOIs)","Risk of medication overuse headache with frequent use","Severe hepatic impairment (Child-Pugh C): contraindicated","Peripheral ischemia and gastrointestinal ischemia"] |
Loading safety data…
| Fetal Monitoring | Monitor maternal blood pressure and heart rate during administration. Assess fetal heart rate patterns if used near term due to potential vasoconstriction. No specific fetal monitoring required for single exposure; however, repeated use warrants assessment of fetal growth and well-being. |
| Fertility Effects | No significant effects on fertility observed in animal studies at doses up to 50 mg/kg/day. Human data are insufficient to determine impact on fertility. Eletriptan may be associated with menstrual irregularities in some women due to effects on serotonin receptors, but no definitive evidence of impaired fertility. |