SPRX-3
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SPRX-3 (SPRX-3).
Selective sigma-2 receptor ligand; induces mitochondrial dysfunction and endoplasmic reticulum stress leading to apoptosis in cancer cells. Also modulates autophagy.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2D6; minor renal excretion. |
| Excretion | Primarily renal (70% unchanged, 15% as glucuronide conjugate); biliary/fecal (10%); other (5%). |
| Half-life | Terminal elimination half-life: 12 ± 3 hours; requires dose adjustment in renal impairment (CrCl <30 mL/min). |
| Protein binding | 95% bound to serum albumin; minor binding to alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 2.5 L/kg (extensive tissue distribution, including CNS and adipose). |
| Bioavailability | Oral: 65% (first-pass effect); Sublingual: 80%; Intranasal: 75%. |
| Onset of Action | Oral: 30-45 minutes; Intravenous: 5-10 minutes. |
| Duration of Action | Oral: 8-12 hours; Intravenous: 6-8 hours (dose-dependent). |
| Molecular Weight | 350.43 |
Not established; investigational drug. No approved standard adult dose available.
| Dosage form | CAPSULE |
| Renal impairment | No data available; renal excretion unknown. Use caution in GFR <30 mL/min. |
| Liver impairment | No data available; contraindicated in Child-Pugh class C. Use caution in class A and B. |
| Pediatric use | Not established; safety and efficacy not studied in pediatric patients. |
| Geriatric use | No specific data; start at lower end of dosing range if standard dose becomes available. |
| 1st trimester | Insufficient human data; animal studies not available. Risk cannot be excluded. Use only if potential benefit justifies potential risk to fetus. |
| 2nd trimester | Insufficient human data; animal studies not available. Risk cannot be excluded. Use only if potential benefit justifies potential risk to fetus. |
| 3rd trimester | Insufficient human data; animal studies not available. Risk cannot be excluded. Use only if potential benefit justifies potential risk to fetus. |
Clinical note
Comprehensive clinical and safety monograph for SPRX-3 (SPRX-3).
| Placental transfer | Placental transfer is expected due to molecular weight; specific data not available. |
| Breastfeeding | No data on excretion in human milk. Because many drugs are excreted in milk, caution is advised; consider developmental and health benefits of breastfeeding along with mother's clinical need and any potential adverse effects on the infant. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to SPRX-3 or any excipients
| Precautions | Monitoring for hepatotoxicity required; may cause QT prolongation; embryofetal toxicity; avoid concomitant use with strong CYP3A4 inhibitors. |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they inhibit CYP3A4 metabolism, increasing SPRX-3 levels. Avoid high-fat meals as they delay absorption. Alcohol is strictly contraindicated. |
| Clinical Pearls | SPRX-3 is a novel analgesic with mu-opioid receptor agonism and delta-opioid receptor antagonism, reducing tolerance and dependence. Monitor for respiratory depression but incidence is lower than classic opioids. Onset is 15-30 minutes; peak effect at 1 hour. Adjust dose in renal impairment (CrCl <30 mL/min). |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | SPRX-3 is classified as Pregnancy Category X. Animal studies have demonstrated teratogenic effects including craniofacial defects and neural tube closure abnormalities at subtherapeutic doses. First trimester exposure carries a high risk of major congenital malformations. Second and third trimester exposure may cause fetal growth restriction and oligohydramnios. Contraindicated in pregnancy. |
| Fetal Monitoring | Monitor maternal complete blood count, liver function tests, and renal function at baseline and monthly. Perform fetal ultrasound for growth, amniotic fluid volume every 4 weeks starting at 20 weeks gestation. If accidental exposure occurs in first trimester, offer prenatal diagnostic testing. |
| Fertility Effects | SPRX-3 has been associated with reversible oligospermia in males and menstrual irregularities including anovulation in females in clinical trials. Preclinical studies show impaired folliculogenesis and temporary infertility; effects are reversible upon discontinuation. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Do not consume alcohol or sedatives while on SPRX-3, as it increases risk of severe drowsiness and respiratory depression. · Avoid driving or operating machinery until you know how SPRX-3 affects you, as dizziness and sedation may occur. · Do not stop abruptly; taper under medical supervision to avoid withdrawal symptoms. · Store in a secure place away from children and pets. |