Phase 2 N=24 Randomized Triple-blind Treatment

Tariquidar-ondansetron Combination in Neuropathic Pain

Neuropathic Pain

Bottom Line

View on ClinicalTrials.gov: NCT04603066 ↗

Enrolled (actual)

Serious AEs

0.0%

Results posted

Aug 2025

Primary outcome: Primary: Concertation-time Profile of Ondansetron in Plasma, Measured by the Area Under the Concentration-time Curve (AUC) — 0.89; 0.87 mg*hr/L — p=0.8651

Study Design & Population

Study type: Interventional
Phase: Phase 2
Interventions: Ondansetron 16 mg with Tariquidar (Drug); Ondansetron 16 mg with Placebo (Drug)
Age: Adult, Older Adult · 18+ yrs
Sex: All
Sponsor: Washington University School of Medicine
Primary completion: Oct 2023

Outcome Measures

Outcome	Result	p-value
PRIMARY Concertation-time Profile of Ondansetron in Plasma, Measured by the Area Under the Concentration-time Curve (AUC)	0.89; 0.87	0.8651
PRIMARY Cerebrospinal Fluid to Plasma Concentration Ratio of Ondansetron	0.132; 0.112	0.056
SECONDARY % Change in Pain Intensity	37.2; 28.8	—
SECONDARY Conditioned Pain Modulation (CPM) Magnitude (ΔCPM)	0.1; 1.8	—
SECONDARY Correlation Between CPM Magnitude (ΔCPM) and Change in Pain Intensity	0.02; 0.01	—
SECONDARY Change in Neuropathic Pain Symptom Inventory (NPSI) Score	-8.6; -13.2	—

Summary

Prospective, randomized, double-blind, placebo controlled, cross-over proof of concept study. To determine the pharmacokinetics and tolerability of co-administration of 5-HT3R antagonist ondansetron with a P-glycoprotein inhibitor tariquidar, in patients with neuropathic pain.

Eligibility Criteria

Inclusion Criteria

Age 18-65;
Documented diagnosis of neuropathic pain due to damage or disease affecting the peripheral nervous system;
At least Probable neuropathic pain grading1;
Pain duration >3 months;
Average pain intensity ≥4 on 0-10 numerical rating scale (NRS).

Exclusion Criteria

Current pregnancy or lactation;
Moderate-severe kidney or liver dysfunction;
Active cardiac arrhythmias (non-sinus rhythm), Long QT syndrome, or QTc interval >450msec;
Congestive heart failure
Abnormal troponin values at screening visit;
Current treatment with MAO inhibitors, mirtazapine, SSRI antidepressants, or SNRI medications duloxetine or venlafaxine;
Current treatment with tapentadol, tramadol, or fentanyl;
Current treatment with P-glycoprotein substrate drugs with narrow therapeutic window, e.g. digoxin;
Current treatment with tricyclic antidepressant medications (e.g. amitriptyline, desipramine, imipramine) at a dose >25mg/day;
Ongoing use of any of the following medications with known effects on Pgp function: carbamazepine, phenytoin, phenobarbital, cyclosporine, clarithromycin, erythromycin, ritonavir, verapamil, rifampicin, St. John's wort;
Current treatment with QT-prolonging drugs, and drugs known to have a significant interaction with ondansetron or other P-glycoprotein substrates (see section 2.3.3.);
Current treatment with anticoagulant drugs;

View full record on ClinicalTrials.gov →

Data sourced from ClinicalTrials.gov (NCT04603066). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication.