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In this experiment the investigators would like to assess if papain induces an itch sensation comparable to the itch sensation induced by cowhage and to confirm that the mechanism of action of papain follows the non-histaminergic pathway.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Doxepin Application | Experimental | During the session each forearm of the subject will be divided into four squared areas (2.5x2.5 cm), see Figure 4. Four of the areas will be treated with doxepin for 1 hour and 30 minutes (with a patch to deposit 1.2 grams of cream). Each patch will be covered with Tegaderm I.V., an occlusive, adhesive dressing (3M), for at least 1½ hours 48. At the end of the pre-treatment period, the patches will be removed and the skin will be cleaned with alcohol. |
|
| Itch Induction | Experimental | After Doxepin removal, Then tests with papain, cowhage, histamine or vehicle will be conducted. Each substance will be randomly applied in two areas, one pretreated with doxepin and one with no pre-treatment. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Doxepin Topical | Drug | Four of the areas will be treated with doxepin for 1 hour and 30 minutes (with a patch to deposit 1.2 grams of cream). Each patch will be covered with Tegaderm I.V., an occlusive, adhesive dressing (3M), for at least 1½ hours |
| Measure | Description | Time Frame |
|---|---|---|
| Superficial blood perfusion | Superficial blood perfusion is measured by a Speckle contrast imager (FLPI, Moor Instruments, England). | 15 minutes |
| Measuring itch intensity by computerized Visual Analog Scale Scoring | The subjects will rate the sensation of itch on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates "no itch" and 100 indicates "worst itch imaginable" and similarly for sensations of stinging/pricking and burning, both of which are frequently associated with the sensation of itch. | 15 minutes |
| Measuring pain intensity by computerized Visual Analog Scale Scoring | The subjects will rate the sensation of pain on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates "no pain" and 100 indicates "worst pain imaginable". | 15 minutes |
| Measuring Alloknesis | Alloknesis is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 milliNewton of force). This stimulator is applied 0.5 cm outside the area of itch provocation. | 15 minutes |
| Measure | Description | Time Frame |
|---|---|---|
| Measurement of Cold Detection Thresholds (CDT) | The tests for thermal sensation will all be conducted using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature decreases 1°C per second from a starting temperature of 32°C until the subject perceives a temperature change (cold sensation) and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 0°C will be used. |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Aalborg University | Aalborg | North Denmark | 9000 | Denmark |
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| ID | Term |
|---|---|
| D011537 | Pruritus |
| ID | Term |
|---|---|
| D012871 | Skin Diseases |
| D017437 | Skin and Connective Tissue Diseases |
| D012877 | Skin Manifestations |
| D012816 | Signs and Symptoms |
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| ID | Term |
|---|---|
| D004316 | Doxepin |
| D010206 | Papain |
| D006632 | Histamine |
| ID | Term |
|---|---|
| D010082 | Oxepins |
| D004988 | Ethers, Cyclic |
| D004987 | Ethers |
| D009930 | Organic Chemicals |
| D003990 |
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| Papain | Drug | Papain will be applied by 1 SPT prick thought the skin |
|
| Histamine | Drug | Histamine will be applied by 1 SPT prick thought the skin |
|
| Cowhage | Other | Cowhage spicules are 1-2 mm in length and have diameter of 1-3 µm at their tip. 30-35 spicules are gently rubbed into a 1 cm diameter skin area. |
|
| 15 minutes |
| Measurement of Cold PainThresholds (CPT) | The tests for thermal sensation will all be conducted using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature decreases 1°C per second from a starting temperature of 32°C until the subject perceives a temperature change (cold sensation) and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 0°C will be used. | 15 minutes |
| Measurement of Heat Pain Thresholds (HPT) | The tests for thermal sensation will all be performed using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature raises 1°C per second from a starting temperature of 32°C until the subject detects a painful sensation and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 52°C will be used. | 15 minutes |
| Measurement of Warm Detection Thresholds (WDT) | The tests for thermal sensation will all be performed using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. During the first 8 seconds, the temperature raises 1°C per second from a starting temperature of 32°C until the subject detects a painful sensation and presses a button that will terminate the measurement and return the temperature to baseline at a rate of 5°C /s. A cut-off temperature of 52°C will be used. | 15 minutes |
| Measurement of Pain to Supra-threshold Heat Stimuli | The tests will be conducted by using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. The subjects will have to rate the pain to two suprathreshold heat pain stimuli (starting and ending at 32°C with an increase and decrease of 5°C and 3 s plateau at 50°C). | 15 minutes |
| Measurement of Mechanical Pain Thresholds (MPT) | This test is conducted using a pin-prick set (Aalborg University, Aalborg). This test is conducted using a pin-prick set (Aalborg University, Aalborg).easurement of Mechanical Pain Thresholds (MPT) | 15 minutes |
| Measurement of Mechanical Pain Sensitivity (MPS) | This test is conducted using a pin-prick set (Aalborg University, Aalborg). | 15 minutes |
| Touch Pleasantness (TP) | Pleasant touch sensation measured using astandardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN. | 15 minutes |
| D013568 | Pathological Conditions, Signs and Symptoms |
| Dibenzoxepins |
| D006575 | Heterocyclic Compounds, 3-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |
| D006571 | Heterocyclic Compounds |
| D003546 | Cysteine Endopeptidases |
| D057056 | Cysteine Proteases |
| D010447 | Peptide Hydrolases |
| D006867 | Hydrolases |
| D004798 | Enzymes |
| D045762 | Enzymes and Coenzymes |
| D010450 | Endopeptidases |
| D015306 | Biogenic Monoamines |
| D001679 | Biogenic Amines |
| D000588 | Amines |
| D005021 | Ethylamines |
| D007093 | Imidazoles |
| D001393 | Azoles |
| D006573 | Heterocyclic Compounds, 1-Ring |
| D012898 | Autacoids |
| D018836 | Inflammation Mediators |
| D001685 | Biological Factors |