Table 3.
Schematic overview of studies involving paracetamol in human experimental pain models
| Reference | Dose | Model (pain assessment) | Findings | |
|---|---|---|---|---|
| Acute models | [39] (n= 18) | 1000 mg p.o. | Electrical skin and muscle stimulation, PTT | No parameters were affected |
| Deep pressure, PTT | ||||
| IM hypertonic saline AUCVAS | ||||
| [42] (n= 18) | 1000 mg p.o. | Cold pressor test | PTT↓ both before and after cold pressor test. Effect more pronounced after | |
| PTT to deep pressure before and after cold water immersion | ||||
| [40] (n= 24) | 1000 mg p.o. | Stimulation of nasal mucosa by CO2 (phasic pain) and dry air (tonic pain), VAS, evoked brain potentials (only phasic pain) | VAS after phasic pain ↔ | |
| VAS after tonic pain ↓ | ||||
| Amplitudes of evoked potentials ↓ | ||||
| [41] (n= 22) | 1000 mg i.v. (prodrug) | Deep pressure, PTT | PTT ↔ | |
| [37] (n= 10) | 500, 1000 (normal release) and 2000 (sustained release) mg p.o. | Laser skin stimulation, PDT | Normal release: PDT ↑ | |
| Sustained release: PDT ↔ | ||||
| [38] (n= 32) | 1000 mg p.o. | Intracutaneous electrical stimulation, VAS, evoked brain potentials | VAS ↓ | |
| Evoked potentials: power spectrum was altered and amplitudes ↓ | ||||
| [36] (n= 15) | 1000 mg p.o. normal release and 2000 mg p.o. slow release | Laser skin stimulation, PDT, evoked brain potentials | Pain threshold ↑ | |
| Evoked potentials ↔ | ||||
| Dosing regimes were alike | ||||
| Models inducing hyperalgesia | [32] (n= 24) | 1000 mg p.o. | Freeze lesion: | No parameters were affected |
| area of secondary HA to pinprick stimulation | ||||
| [43] (n= 17) | 75 mg p.o. | Continuous electrical skin stimulation Ongoing pain (numeric rating scale) | Area of HA and allodynia ↓ | |
| Ongoing pain ↔ | ||||
| Area of secondary HA to pinprick (von Frey) | ||||
| [44] (n= 14) | 1000 mg i.v. | Continuous intracutaneous electrical stimulation, ongoing pain (VAS), area of secondary HA to pinprick and allodynia to stroking | Area of HA and allodynia ↓ | |
| Ongoing pain ↔ |
In the column ‘Model’ the method for pain assessment is normal font, and the method for pain induction is bold. PDT, pain detection threshold; PTT, pain tolerance threshold; AUC, area under curve; VAS, visual analogue scale; HA, hyperalgesia.