Pharmacokinetic-Pharmacodynamic Correlations of Analgesics
Hartmut Derendorf, Günther Hochhaus in Handbook of Pharmacokinetic/Pharmacodynamic Correlation, 2019
Alfentanil is an opioid analgesic with an extremely rapid onset and short duration of action as a result of its limited biodistribution and high lipid solubility. The drug rapidly equilibrates between blood and brain tissue and binds to µ-receptors in the CNS. An excellent correlation between the rise and decline of alfentanil concentrations in plasma with the onset and recovery of EEG changes has been demonstrated, indicative of narcotic effect (Figure 5).95 PK-PD analysis revealed a smaller hysteresis, as indicated by a smaller t1/2 kco of approximately 1 min, with alfentanil compared to fentanyl.95 This difference may be due to the larger brain-blood partition coefficient for fentanyl. Moreover, a steep relationship between concentration and effect was observed which is typical for narcotic analgesics.84,85 The Css50 was found to be 520 ng/ml which is approximately 75 times higher than that of fentanyl, i.e., alfentanil is 75 times less potent than fentanyl.
Clinical pharmacology: opioids
Pamela E Macintyre, Suellen M Walker, David J Rowbotham in Clinical Pain Management, 2008
Remifentanil is a μ-opioid receptor agonist with an analgesic potency similar to that of fentanyl.106 It is a fentanyl derivative which is broken down by blood and tissue esterases.106 Its speed of onset is similar to that of alfentanil.107 It has a short and predictable half-life which is not affected by hepatic or renal function108 or plasma cholinesterase (butyrylcholinesterase or pseudocholinesterase) deficiency. The main metabolic product of ester hydrolysis is a carboxylic acid derivative (GI-90291) which is excreted by the kidneys (elimination half-life approximately 100 minutes).109 Although its elimination is delayed in renal failure, significant pharmacological effects are unlikely as its potency relative to remifentanil is only 0.1–0.3 percent.110
Medicines in neonates
Evelyne Jacqz-Aigrain, Imti Choonara in Paediatric Clinical Pharmacology, 2021
Alfentanil is a synthetic opioid that is chemically a derivate of fentanyl. Sufficient analgesia during endotracheal intubation and suctioning has been found using 10–20 mcg/kg alfentanil in preterm neonates [41–43]. Alfentanil plasma protein binding varies from 65% in preterm neonates to 79% in term infants (44,45). Clearance of alfentanil is reduced in the neonate (20–60 mlmin_1-70kg_1). Consequently, the elimination half-life is higher in the neonatal period, especially in premature neonates (6–9 hours) [46,47]. Alfentanil cannot be used without neuromuscular blocking drugs in newborns, because of a very high incidence of rigidity [41,48].
Risk factors for underestimation of patient pain in outpatient colonoscopy
Published in Scandinavian Journal of Gastroenterology, 2022
Jessica Ryhlander, Gisela Ringström, Björn Lindkvist, Per Hedenström
With the intent to minimize patient pain and discomfort, intravenous administration of opiate analgesic (alfentanil) and/or benzodiazepine (midazolam) was offered to all patients. At the time of this study, propofol was not a part of routine medication. At the very start of the procedure, patients accepting medication were given an initial dose of 1–2 milligrams of midazolam and 0.25–0.50 milligrams of alfentanil with respect to age and body weight. If needed, repeated doses of alfentanil (0.25 mg) and midazolam (1 mg) were administered during the procedure. All supplementary doses were approved by the endoscopist, but such administration could be initiated by both the endoscopist and the endoscopy assistant. Importantly, excessive medication was avoided to enable adequate patient collaboration and repositioning during the procedure, which in turn facilitates intubation and thereby minimizes patient pain and discomfort.
Women require routine opioids to prevent painful colonoscopies: a randomised controlled trial
Published in Scandinavian Journal of Gastroenterology, 2021
Anna Lisa Schult, Edoardo Botteri, Geir Hoff, Øyvind Holme, Michael Bretthauer, Kristin Ranheim Randel, Elisabeth Haagensen Gulichsen, Badboni El-Safadi, Ishita Barua, Carl Munck, Linn Rosén Nilsen, Hege Marie Svendsen, Thomas de Lange
Participants given fentanyl before colonoscopy reported less painful colonoscopies with no difference in adverse events, recovery time, or willingness to repeat examination compared to fentanyl on-demand. Fentanyl before colonoscopy should be recommended to women aged 55–79. Alfentanil is theoretically a better on-demand analgesic agent. However, we could not demonstrate a beneficial effect and further trials with better-defined titration of the dose and improved information to the staff to pause the procedure until the effect of the medication are achieved are required to finally conclude whether alfentanil in monotherapy should be the preferred choice for women who prefer on-demand medication during colonoscopy.
Related Knowledge Centers
- Anesthesia
- REMifentanil
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- Circulatory System
- Opioid
- Analgesic
- Medication
- Fentanyl
- Μ-Opioid Receptor