Effects of 5HTP on the Injured Human Spinal Cord (5-HTP only)
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ClinicalTrials.gov Identifier: NCT04520178 |
Recruitment Status :
Active, not recruiting
First Posted : August 20, 2020
Last Update Posted : October 17, 2022
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Condition or disease | Intervention/treatment | Phase |
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Spinal Cord Injuries | Drug: 5-Hydroxytryptophan 100 MG Drug: 5-Hydroxytryptophan Drug: Carbidopa Drug: Placebo | Phase 2 Phase 3 |
This study will assess for the first time the effects of 5-HTP on neural excitability utilizing a combination of neurophysiological and functional testing in subacute motor complete (AIS A/B), chronic motor complete (AIS A/B) and chronic incomplete (AIS C/D) SCI participants. To reduce peripheral side effects such as nausea, these supplements will be co-administered with carbidopa which inhibits the action of peripheral AADC, thereby ensuring that 5-HTP can effectively cross the blood brain barrier prior to being broken down. The neurophysiological outcomes will allow for the determination of the mechanistic actions of each pharmacological agent on different pathways/sites within the central nervous system in three different patient populations with varying degrees of lesion severity and will for the determination of whether increased Amino Acid Decarboxylase (AADC) expression and therefore the efficacy of this approach is correlated to lesion severity and/or chronicity. Importantly, the use of functional testing will allow for the determination of whether these often-reported neurophysiological changes translate to improvements in muscle activation patterns and kinematics during cycling.
The effects of 5-HTP will be assessed across three different participant groups: i) subacute (6 months-1 year) AIS A/B SCI individuals, ii) chronic (>2 years post injury) AIS A/B SCI individuals and iii) chronic AIS C/D SCI individuals.. In a placebo-controlled, randomized crossover design, participants will receive i) 50 mg 5HTP combined with 50 mg carbidopa, ii) 100 mg 5-HTP combined with 50 mg carbidopa, iii) 50 mg carbidopa only or iv) placebo. Ten participants will be recruited in each group. Participants will visit the lab on four separate occasions, separated by at least 72 hours.
Study Type : | Interventional (Clinical Trial) |
Estimated Enrollment : | 30 participants |
Allocation: | Randomized |
Intervention Model: | Crossover Assignment |
Masking: | Double (Participant, Outcomes Assessor) |
Primary Purpose: | Basic Science |
Official Title: | Effects of the Serotonin Precursor, 5-hydroxytryptophan, in the Injured Human Spinal Cord |
Actual Study Start Date : | July 1, 2020 |
Estimated Primary Completion Date : | June 30, 2023 |
Estimated Study Completion Date : | June 30, 2024 |

Arm | Intervention/treatment |
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Active Comparator: Low-dose 5HTP
50mg 5-HTP in combination with 50mg carbidopa
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Drug: 5-Hydroxytryptophan
50mg combined with 50mg carbidopa Drug: Carbidopa 50mg |
Active Comparator: High-dose 5HTP
100mg 5-HTP in combination with 50mg carbidopa
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Drug: 5-Hydroxytryptophan 100 MG
100mg combined with 50mg carbidopa Drug: Carbidopa 50mg |
Sham Comparator: Carbidopa
50mg carbidopa only
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Drug: Carbidopa
50mg |
Placebo Comparator: Placebo
Placebo comparator
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Drug: Placebo
Placebo |
- Change in motoneuron excitability [ Time Frame: Pre drug-intake, 30minutes, 60minutes, 90minutes and 120minutes post drug-intake ]F waves
- Change in spinal excitability [ Time Frame: Pre drug-intake, 30minutes, 60minutes, 90minutes and 120minutes post drug-intake ]H reflex
- Change in flexor reflex/spasms [ Time Frame: Pre drug-intake, 30minutes, 60minutes, 90minutes and 120minutes post drug-intake ]Cutaneomuscular reflex
- Change in functional movement performance [ Time Frame: Pre drug-intake, 120-150minutes post drug-intake ]Leg cycling task
- Serum analysis of 5HIAA [ Time Frame: 90-120minutes post drug-intake ]5-HIAA (serum)
- Serum analysis of serotonin [ Time Frame: 90-120minutes post drug-intake ]5-HT (serum and whole blood), cortisol
- Serum analysis of cortisol [ Time Frame: 90-120minutes post drug-intake ]serum cortisol
- Whole blood analysis of Serotonin [ Time Frame: 90-120minutes post drug-intake ]Blood 5HT

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Ages Eligible for Study: | 18 Years to 65 Years (Adult, Older Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | No |
Inclusion Criteria:
- participants must have suffered trauma to the spinal cord at least six months ago or longer
Exclusion Criteria:
- individuals with damage to the nervous system other than to the spinal cord
- pregnant and/or breastfeeding women
- alcoholic participants
- history of seizure/epilepsy
- history of suicidal thoughts or behaviors
- known or suspected allergy to the medication ingredients
- cardiovascular disease including history of heart attack or heart rhythm irregularities
- coronary artery disease
- reduced liver function or disease
- reduced kidney function or disease
- lung disease
- comatose or depressed states due to CNS depressants
- endocrine dysfunction
- blood dyscrasias or blood related disease
- bone marrow depression
- hypocalcemia
- history of stomach ulcers
- wide angle glaucoma
- phenylketonuria
- history of tumors
- uncontrolled heart problems
- unstable psychiatric or mental disorder
Participants taking:
- monoamine oxidase inhibitor therapy
- serotonergic antidepressants
- tricyclic antidepressants
- any type of serotonergic agonist
- dopamine D2 receptor antagonists
- amphetamine
- CNS depressants
- levodopa
- lithium
- anti-hypertensive drugs
- iron salts
- metoclopramide
- phenothiazine medication

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT04520178
United States, Kentucky | |
University of Louisville | |
Louisville, Kentucky, United States, 40292 | |
Canada, Alberta | |
University of Alberta | |
Edmonton, Alberta, Canada, T6G-2E1 |
Principal Investigator: | Jessica D'Amico, PhD | University of Alberta |
Responsible Party: | University of Alberta |
ClinicalTrials.gov Identifier: | NCT04520178 |
Other Study ID Numbers: |
Pro00119483 |
First Posted: | August 20, 2020 Key Record Dates |
Last Update Posted: | October 17, 2022 |
Last Verified: | October 2022 |
Studies a U.S. FDA-regulated Drug Product: | Yes |
Studies a U.S. FDA-regulated Device Product: | No |
Spinal Cord Injuries Spinal Cord Diseases Central Nervous System Diseases Nervous System Diseases Trauma, Nervous System Wounds and Injuries Carbidopa 5-Hydroxytryptophan Antiparkinson Agents Anti-Dyskinesia Agents |
Dopamine Agents Neurotransmitter Agents Molecular Mechanisms of Pharmacological Action Physiological Effects of Drugs Aromatic Amino Acid Decarboxylase Inhibitors Enzyme Inhibitors Antidepressive Agents, Second-Generation Antidepressive Agents Psychotropic Drugs |