Try our beta test site
IMPORTANT: Listing of a study on this site does not reflect endorsement by the National Institutes of Health. Talk with a trusted healthcare professional before volunteering for a study. Read more...

Safety and Efficacy Study of Ethosuximide for the Treatment of Complex Regional Pain Syndrome (CRPS)

This study has been terminated.
(Recruitment difficult and enrolment low: decision was made to stop the study.)
McGill University
Information provided by:
McGill University Health Center Identifier:
First received: May 29, 2008
Last updated: May 11, 2011
Last verified: May 2011
Pain remains the most debilitating symptom for adult patients suffering from complex regional pain syndrome (CRPS). Most CRPS patients gain little to no relief from current painkillers. The purpose of this study is to evaluate the efficacy and safety of ethosuximide in search of much-needed adjunctive therapy to relieve the pain and suffering associated with CRPS.

Condition Intervention Phase
Complex Regional Pain Syndromes
Drug: Placebo
Drug: Ethosuximide
Phase 2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
Official Title: A Single Centre. Parallel-Group, Double-Blinded, Randomized, Placebo-Controlled Pilot Clinical Trial on Ethosuximide for the Treatment of Complex Regional Pain Syndrome (CRPS)

Resource links provided by NLM:

Further study details as provided by McGill University Health Center:

Primary Outcome Measures:
  • Maximum tolerated dose (500mg-1500mg per day) and Safety profile [ Time Frame: up to 10 weeks ]
    Primary outcomes will consist of the dose attained during the study and the safety (adverse event) profile. Maximum timeframe on study drug is 6 weeks. Adverse events will be collected up to one month after the trial period ends.

Secondary Outcome Measures:
  • Pain Intensity Scores on the Visual Analogue Scale (VAS) [ Time Frame: up to 7 weeks ]
    Pain Intensity captured on Day 1 (First study visit post-disallowed drug cessation period) and 7 days after maximal-tolerated dose attained (Final Study Visit)

  • Pain Intensity Scores on the Numerical Rating Scale (NRS) [ Time Frame: up to 5 weeks ]
    Pain Intensity using the Numerical Rating Scale will be captured by telephone every week during dose titration period (Days 3 and 6).

  • Neuropathic Pain Symptom Inventory (NPSI) [ Time Frame: up to 7 weeks ]
    Day 1 (First study visit post-disallowed drug cessation period) and 7 days after maximal-tolerated dose attained (Final Study Visit)

  • Short Form 12v2 (SF-12v2) [ Time Frame: up to 7 weeks ]
    Quality of Life measured on Day 1 (First study visit post-disallowed drug cessation period) and 7 days after maximal-tolerated dose attained (Final Study Visit)

  • Short Form McGill Pain Questionnaire (SF-MPQ) [ Time Frame: up to 7 weeks ]
    Day 1 (First study visit post-disallowed drug cessation period) and 7 days after maximal-tolerated dose attained (Final Study Visit)

Enrollment: 4
Study Start Date: September 2008
Study Completion Date: July 2010
Primary Completion Date: July 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Placebo Comparator: 1 Drug: Placebo
250mg matching placebo capsules
Experimental: 2 Drug: Ethosuximide
500-1500mg/day over a 1-5 week dose titration period until maximal tolerated dose (MTD) attained, followed by 1 week MTD plateau period.
Other Name: Zarontin

Detailed Description:

This is a single centre, parallel-group, double-blind, randomized, placebo-controlled pilot clinical trial for adults suffering from complex regional pain syndrome (CRPS).

Twelve (12) subjects diagnosed with CRPS will be enrolled and randomized to receive orally, either ethosuximide or placebo. If the maximum trial medication dosage (1500mg) is reached, the subject will be in the study for a maximum of 10 weeks from screening (Clinic Visit 1) to the end of the drug cessation period. The minimum period a subject could complete the study would be 4 weeks presuming they were not previously on any disallowed drugs and only found the 500mg dose tolerable.


Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Male or female, age ≥18 years old;
  • Diagnosis of Complex Regional Pain Syndrome (CRPS) using International Association for the Study of Pain criteria >6 months;
  • Normal liver function (AST level <3x normal level);
  • Normal kidney function (serum creatinine <133µmol/L);
  • Full blood count, haematocrit >38%;
  • Willing and able to give informed consent and of completing study questionnaires;
  • Stable (no change in past two months) but suboptimal pain pharmacotherapy (i.e. additional pain control felt by patient and physician to be necessary);
  • Able to attend research centre according to the visit schedule;
  • Women of child-bearing potential must be using a reliable form of contraception i.e. oral contraceptives, a barrier method (condom or diaphragm), intra-uterine device or abstinence.

Exclusion Criteria:

  • Optimal response to opioids, antidepressants, anticonvulsants or anti- inflammatory medications;
  • Any history or indication of kidney or liver disease;
  • Any history of alcohol abuse;
  • Presence of diabetes;
  • Subjects taking other anti-epileptic drugs, including gabapentin, pregabalin, topiramate, phenytoin, carbamazepine, and oxcarbazepine;
  • Pregnancy (a serum bHCG pregnancy test will be performed as part of the initial blood panel);
  • Known or suspected allergy to succinimides, ethosuximide, methsuximide (Celontin®), phensuximide;
  • Any history of mental illness or disorder, which in the investigators opinion, interferes with the subjects ability to accurately report treatment response;
  • Participation in other clinical trial in the 30 days prior to enrolment.
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00689585

Canada, Quebec
McGill University Health Centre
Montreal, Quebec, Canada, H3G 1A4
Sponsors and Collaborators
McGill University Health Center
McGill University
Principal Investigator: Mark A Ware, MD McGill University Health Center
  More Information

Responsible Party: Mark A. Ware, Prinicipal Investigator, McGill University Health Centre - Pain Centre Identifier: NCT00689585     History of Changes
Other Study ID Numbers: GEN#07-062
Study First Received: May 29, 2008
Last Updated: May 11, 2011

Keywords provided by McGill University Health Center:
Complex Regional Pain Syndrome
Reflex Sympathetic Dystrophy
Chronic Pain

Additional relevant MeSH terms:
Somatoform Disorders
Complex Regional Pain Syndromes
Reflex Sympathetic Dystrophy
Pathologic Processes
Mental Disorders
Autonomic Nervous System Diseases
Nervous System Diseases
Peripheral Nervous System Diseases
Neuromuscular Diseases
Anticonvulsants processed this record on May 23, 2017