RELPAX
Clinical safety rating
cautionComprehensive clinical and safety monograph for RELPAX (RELPAX).
Comprehensive clinical and safety monograph for RELPAX (RELPAX).
Acute treatment of migraine with or without aura in adultsAcute treatment of migraine in children aged 6-17 years (FDA-approved for ≥40 kg)
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. |
| Molecular Weight | 382.52 |
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 | Limited human data; animal studies show no teratogenic effects at clinically relevant doses. Use only if clearly needed. |
| 2nd trimester | No well-controlled studies; potential for uterine hypertonus and reduced placental blood flow. Avoid unless benefit justifies risk. |
| 3rd trimester | Risk of uterine hypertonus, fetal hypoxia, and neonatal adverse effects (e.g., irritability, jitteriness). Avoid during labor. |
Clinical note
Comprehensive clinical and safety monograph for RELPAX (RELPAX).
| Placental transfer | Eletriptan crosses the human placenta; detectable in fetal blood at concentrations similar to maternal. |
| Breastfeeding | Excreted into breast milk in low amounts; estimated relative infant dose <5% of maternal dose. Caution in infants with low body weight or hepatic impairment. |
| Lactation Rating | L2 (Probably Compatible) |
| 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. |
| 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. |
■ 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 diseaseUncontrolled hypertensionHemiplegic or basilar migraineHistory of stroke or transient ischemic attackConcomitant use with other 5-HT1 receptor agonists (triptans) or ergot alkaloids within 24 hoursSevere hepatic impairment (Child-Pugh C)
| 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 |
| Food/Dietary | No significant food interactions. Grapefruit may increase eletriptan levels; avoid grapefruit juice. |
| Clinical Pearls | Relpax (eletriptan) is a 5-HT1B/1D receptor agonist used for acute migraine. Avoid within 24 hours of other triptans or ergotamines. Contraindicated in patients with ischemic heart disease, uncontrolled hypertension, or hemiplegic/basilar migraine. Onset of action can be as early as 30 minutes. Maximum dose is 40 mg per 24 hours; single dose of 20 mg is effective for many. Consider shorter triptan half-life (4 hours vs sumatriptan's 2) for patients needing rapid clearance. Not effective for migraine prophylaxis. |
| Patient Advice | Take at the first sign of migraine; do not use for prevention. · Do not take more than one dose within 24 hours; maximum 40 mg. · Avoid within 24 hours of other triptans or ergotamine-containing medications. · Seek emergency care if chest pain, shortness of breath, or severe allergic reaction occurs. · Do not use if you have a history of heart disease, stroke, or uncontrolled high blood pressure. · May cause dizziness or drowsiness; avoid driving until you know how it affects you. |
Loading safety data…