Clinical trial NCT04647877: Phenytoin Cream for the Treatment of Neuropathic Pain
Official title: Enrichment Randomized Double-blind, Placebo-controlled Cross-over Trial With PHEnytoin Cream in Patients With Painful Chronic Idiopathic Axonal polyNEuropathy
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE2
PHASE3
Conditions: Chronic Idiopathic Axonal Polyneuropathy
Keywords: cryptogenic sensory polyneuropathy
CIAP
neuropathic pain
Lead sponsor: UMC Utrecht
Sponsor class: OTHER
Collaborators: name: Princess Beatrix Muscle Foundation
name: Dr. C.J. Vaillant Fonds
First posted: 2020-12-01
Enrollment: 81
Sex: ALL
Minimum age (years): 40
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: TREATMENT

Brief summary: Objectives: The main objective is to evaluate the efficacy and safety of phenytoin cream in patients with neuropathic pain due to chronic idiopathic axonal polyneuropathy (CIAP). The second objective is to determine the predictive value of a double-blind placebo-controlled response test (DOBRET) to identify sustained responders.

Study design: This is a 6-week enrichment randomized double-blind, placebo-controlled cross-over trial evaluating phenytoin cream in 84 participants with painful CIAP, whereafter an open label extension phase is offered with phenytoin 20 percent cream for up to one year.

At baseline a DOBRET with phenytoin 10 percent and placebo cream will be performed in each study participant to stratify participants according to their response to the DOBRET before entering the double-blind cross-over phase. DOBRET positive participants are those who experience at least two points pain reduction on the 11-point numerical rating scale (NRS) on the phenytoin 10 percent cream applied area within 30 minutes and at least one-point difference in pain reduction on the NRS between phenytoin 10 percent and placebo cream applied area, in favour of the former.

Participants will receive three treatments in a double blind fashion and in a randomized order: phenytoin 10 percent, phenytoin 20 percent and placebo cream. The duration of each treatment period is two weeks. Participants will cross-over two times to each of the other treatments. The study does not have wash-out periods between treatments, because the mean duration of analgesic effect after an application is expected to be less than nine hours. A blood sample will be collected at the end of the second week of the first treatment period to test for phenytoin plasma levels.

Study population: The investigators aim to include 84 participants, age 40 years or older, who have been diagnoses with painful CIAP at the University Medical Center Utrecht and fulfil the inclusion criteria and have given written informed consent.

Interventions: Phenytoin cream in concentrations of 10 percent and 20 percent cream compared to placebo cream.

Primary endpoint: Change in pain intensity measured on the NRS between baseline and week 2 for phenytoin 20% cream versus placebo cream.


Eligibility criteria: Inclusion Criteria:

* Patients have been diagnosed with CIAP defined as: presence of symmetrical distal sensory or sensorimotor symptoms such as numbness, pins and needles, tightness, coldness, unsteadiness, muscle cramps, and weakness with onset in the feet, compatible with polyneuropathy; presence of symmetrical distal sensory or sensorimotor signs with evidence of large nerve fiber involvement such as decreased sense of touch, vibration, and proprioception, usually in the presence of decreased pin prick/temperature sense, decreased/absent tendon reflexes, or slight muscle weakness on neurologic examination, compatible with polyneuropathy; an insidious onset and slow or no progression of the polyneuropathy over the course of at least 6 months; no identifiable cause for the polyneuropathy after thorough history-taking, clinical examination, and extensive laboratory testing; no suggestion of a hereditary polyneuropathy based on detailed kinship history (i.e., one or more affected family member), neurologic examination, or confirmation by genetic analysis; and nerve conduction studies excluding a demyelinating polyneuropathy and confirming large nerve fiber involvement if the findings on neurologic examination are equivocal considering the patient's age.
* Presence of chronic localized neuropathic pain due to CIAP
* Neuropathic pain localized in two anatomically symmetrical areas of feet/lower legs
* Duration of neuropathic pain ≥3 months
* Duration of ≥1 hour neuropathic pain per day
* Neuropathic pain characteristics defined by the Douleur Neuropathique 4 questions (DN4) score ≥4
* Mean pain score during daytime of ≥4 and \<10 on the NRS at study entry (baseline)
* Difference of pain intensity between left and right foot and/or lower leg of not more than 1 point on the NRS
* No changes in neuropathic pain medication for at least 1 month
* Absence of any of the exclusion criteria outlined below

Exclusion Criteria:

* Painful (poly)neuropathy other than CIAP
* Presence of neuropathic pain due to any other condition than CIAP
* Neuropathic pain (distribution, duration, characteristics, intensity) not fulfilling the inclusion criteria
* Pregnancy or planned pregnancy in the study period (will only be asked)
* Use of oral phenytoin
* Open wounds in the neuropathic pain area
* Current use of topical analgesics
* Presence of other pain syndromes such as the widespread pain syndrome or pain in joints
* Presence of serious psychological/psychiatric morbidity
* Addiction to intoxicants
* Hypersensitivity to the study medication (active substance and excipients)
* Insufficient mastery of the Dutch language
* Cognitive impairment and insufficiently capable to understand the purpose of the study

Primary outcomes:
measure: Change in mean pain intensity measured on the 11-point numerical rating scale (NRS) between baseline and week 2 for phenytoin 20% cream versus placebo cream.
timeFrame: Mean baseline vs. mean of second week of each intervention
Secondary outcomes:
measure: Change in mean pain intensity from baseline 11-point numerical rating scale (NRS) to the mean NRS in the second week in double-blind response test in positive and negative participants and all participants combined
timeFrame: Mean baseline vs. mean of second week of each intervention
measure: Change of EuroQol (EQ5-5D-5L) from baseline to the end of the second week of each treatment period
timeFrame: Baseline vs. end of second week of each intervention
measure: Change of Neuropathic Pain Symptom Inventory (NPSI) from baseline to the end of the second week of each treatment period
timeFrame: Baseline vs. end of second week of each intervention
measure: Change of subscales of the Brief Pain Inventory (sBPI) from baseline to the end of the second week of each treatment period
timeFrame: Baseline vs. end of second week of each intervention
measure: Change of the 3 worst pain characteristics from baseline to the end of the second week of each treatment period
timeFrame: Baseline vs. end of second week of each intervention
measure: Change of Patient Global Impression of Change Scale (PGIC) from baseline to the end of the second week of each treatment period
timeFrame: Baseline vs. end of second week of each intervention
measure: 30 percent and 50 percent improvement or more on the NRS compared to placebo within one patient
timeFrame: Baseline vs. end of second week of each intervention
measure: Time of carry-over effects after a treatment period
timeFrame: First week of each intervention
measure: Onset of analgesic effect after application
timeFrame: At the end of second week of each intervention
measure: Duration of analgesic effect
timeFrame: At the end of second week of each intervention
measure: Daily number of cream applications
timeFrame: At the end of second week of each intervention
measure: Percentage of analgesic effect as rated by the participant
timeFrame: At the end of second week of each intervention.
measure: Local and/or systemic side effects
timeFrame: During the 6 weeks of double-blind phase and 1 year open phase
measure: Detection of phenytoin in plasma
timeFrame: At the end of second week of first treatment period
measure: Predictive value of DOBRET
timeFrame: Baseline vs. mean of second week of each intervention
measure: Use of escape pain medication
timeFrame: During the 6 weeks of double-blind phase and 1 year open phase
Other outcomes:
Locations:
city: Utrecht
country: Netherlands
facility: University Medical Center Utrecht
Study officials:
affiliation: UMC Utrecht
name: Alexander FJE Vrancken, MD, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Kopsky DJ, Vrancken AFJE, Keppel Hesselink JM, van Eijk RPA, Notermans NC. Usefulness of a Double-Blind Placebo-Controlled Response Test to Demonstrate Rapid Onset Analgesia with Phenytoin 10% Cream in Polyneuropathy. J Pain Res. 2020 May 1;13:877-882. doi: 10.2147/JPR.S243434. eCollection 2020.
citation: Kopsky DJ, Keppel Hesselink JM. Single-Blind Placebo-Controlled Response Test with Phenytoin 10% Cream in Neuropathic Pain Patients. Pharmaceuticals (Basel). 2018 Nov 12;11(4):122. doi: 10.3390/ph11040122.
citation: Kopsky DJ, Keppel Hesselink JM. Phenytoin Cream for the Treatment for Neuropathic Pain: Case Series. Pharmaceuticals (Basel). 2018 May 28;11(2):53. doi: 10.3390/ph11020053.
citation: Kopsky DJ, Keppel Hesselink JM, Russell AL, Vrancken AFJE. No Detectable Phenytoin Plasma Levels After Topical Phenytoin Cream Application in Chronic Pain: Inferences for Mechanisms of Action. J Pain Res. 2022 Feb 9;15:377-383. doi: 10.2147/JPR.S345347. eCollection 2022.
citation: Kopsky DJ, van Eijk RPA, Warendorf JK, Keppel Hesselink JM, Notermans NC, Vrancken AFJE. Enriched enrollment randomized double-blind placebo-controlled cross-over trial with phenytoin cream in painful chronic idiopathic axonal polyneuropathy (EPHENE): a study protocol. Trials. 2022 Oct 22;23(1):888. doi: 10.1186/s13063-022-06806-8.