Table 2.
Schematic overview of studies involving alfentanil in human experimental pain models
| Reference | Dose | Model (pain assessments) | Main findings | |
|---|---|---|---|---|
| Acute models | [45] (n= 36) | 50–250 ng ml−1 iv for 30 min | Electrical skin stimulation, PTT Heat skin stimulation VAS (0.5°C/s rise to set temperatures) | Electrical PTT↓ Heat pain ↓ |
| [44] (n= 12) | 13.4–126.1 ng ml−1 iv | Electrical skin stimulation, PDT, PTT Heat skin stimulation PDT, PTT(1°C s−1) | Electrical and heat PDT, PTT ↓ | |
| [49] (n= 11) | 25–75 ng ml−1 iv | Warmth and cool (sensory threshold) Heat and cold skin stimulation PDT (1–1.5°C/s) Touch sensory threshold (von Frey) | Sensory threshold ↑ Hot and cold PDT ↔ Sensation from touch ↔ | |
| [48] (n= 16) | 25 and 75 ng ml−1 iv | IM injection of hypertonic saline, AUCVASTranscutaneous and intramuscular electrical stimulation PDT | AUC ↓ Electrical PDT ↓ But only for the high dose | |
| [53] (n= 15) | 60 ng ml−1 iv | Skin and intramuscular single and repeated electrical stimulation, PDT, tonic pain to intramuscular electrical stimulation (pain to 1.5 × PDT for 10 s) Im injection of hypertonic saline, AUCVAS | Electrical PDT ↓ VAS to electrical stim. and hypertonic saline ↓ | |
| [8] (n= 7) | 50–200 ng ml−1 iv | Electrical skin stimulation Heat skin stimulation PTT (2°C s−1), Deep pressure, PTT Cold pressor test, AUCVASIschemic pain AUCVAS | Electrical PTT ↑ Cold pressor test, AUC ↓ Deep pressure PTT ↑ Heat PTT↔ Ischaemic pain AUC ↔ | |
| [52] (n= 10) | 16–65 ng ml−1 iv | Cold pressor test, VAS, McGill pain questionnaire | VAS and bothersomeness (McGill pain questionnaire) ↓ | |
| [47] (n= 12) | 7.5 µg kg−1 followed by 0.1 µg kg−1 min−1 and 15 µg kg−1 followed by 0.3 µg kg−1 min−1 iv | Nocicpetive reflex to sural nerve stimulation Deep pressure, PDT, PTT Argon laser pain Intracutaneous electrical stimulation, VAS Evoked brain potentials (electrical and laser) | Reflex threshold ↑ (dose-response relation) Pressure PDT and PTT ↑ (high dose) Evoked potentials amplitude ↓ Argon laser pain ↓ (high dose) | |
| [46] (n= 8) | 30 µg kg−1 im | Nocicpetive reflex to electrical sural nerve stimulation Heat skin stimulation PTT (laser) Pressure algometry (deep pressure), PDT, PTT Cold pressor test AUCVAS | Reflex threshold ↑ (dose-response relation) Pressure PDT ↔ and PTT ↑ Heat PTT ↓ AUCVAS↓ | |
| [51] (n= 10) | 15 µg kg−1 iv | Electrical stimulation of the teeth Evoked brain potentials Subjective pain report (6 point scale) | Evoked potentials amplitude ↓ Pain was reduced | |
| [50] (n= 25) | 19.6–76.6 ng ml−1 iv | Stimulation of nasal mucosa by CO2VAS, functional magnetic resonance imaging | PDT↓ dose dependently Pain associated brain activation ↓ | |
| Models inducing hyperalgesia | [57] (n= 16) | 70 ng ml−1 iv | Burn injury PDT to pinprick in injured skin, area of secondary HA to pinprick Repeated pinprick AUCVASContinuous electrical skin stimulation PDT to pinprick, area of secondary HA to pinprick, repeated pinprick (AUCVAS), | Pain and HA was reduced for all parameters |
| [49] (n= 11) | 25, 50 and 75 ng ml−1 iv | Intradermal capsaicin, evoked pain (VAS) Area of secondary HA to pinprick (von Frey), heat and allodynia to stroking | Pain from capsaicin↓ Area of secondary HA to pinprick & allodynia to stroking↓, HA to heat ↔ | |
| [32] (n= 12) | 100 ng ml−1 iv | Continuous electrical skin stimulation Evoked pain (threshold to VAS5/10) Area of secondary HA to pinprick (von Frey) and allodynia to stroking | Electrically evoked pain ↓ Area of secondary HA to pinprick ↓ (during infusion) | |
| [55] (n= 12) | 28 µg kg−1 and 7 µg kg−1, iv | Intradermal capsaicin, evoked pain (VAS) Pinprick hyperalgesia and allodynia to stroking | No significant dose-response could be demonstrated | |
| [54] (n= 46) | 200 ng ml−1 iv | Intradermal capsaicin, evoked pain (VAS) Area of secondary HA to pinprick (von Frey) and allodynia to stroking | Pain from capsaicin↓ Area of secondary HA to pinprick & allodynia to stroking↓ |
In the column ‘model’ the method for pain assessment is normal font, and the method for pain induction is bolded. Abbreviations: pain detection threshold (PDT), pain tolerance threshold (PTT), area under curve (AUC), visual analogue scale score (VAS), hyperalgesia (HA).