Epinephrine Reduces Systemic Absorption of Extradural Diacetylmorphine

Abstract

HJ. Epinephrine reduces systemic absorption of extradural diacetylmorphine. Anesth Analg 1986;65:1290-4.The effect of epinephriiie on the vascular absorption of morphine froin the extradural space is uncertain; this study examined the effect of epinephrine on the related but more lipophilic opiate diacetylmorphine (diamorphine, heroin) because any effects of vasoconstriction on diacetylmorphirze absorption should be maxirnally apparent. With this experiment, we hoped to resolve whether epinephrine does or does not alter vascular absorption of extradurally injected opiates. Thirty patierits undergoing lumbar laminectomy were given either extradural diacetylmorphine, 5 mg, extradural diacetylmorphine, 5 mg with 2 :200,000 epinephrine, or 1 :200,000 epinephrine followed 5 min later by 5 mg extradural diacetylmorphine. Plasma morphine concentrations were nreasured by radioimmunoassay because of the rapid conversion ofdiacetylmorphine to morphine in plasma; repeated blood sainples were obtained the first 30 nzin after injection into the epidural space. Significantly lower plasmn morphine levels occurred between 3 and 20 min when epinephrine was added to diacetylmorphine. Peak plasma morphine levels (mean ? SEM) were 179 ? 37 nrnollL with diacetylinorphine alone, 87 5 16 nniollL with diacetylmorphine and epinephrine given together and 44 5 11 nmoll L with epinephrine pretreatnzent, all significantly different from one another. The nreair peak plasma morphine concentration was 8.7 ? 1.1 inin for diacetylmorphirzealone, but addition of epinephrine (together or sequentially) rneant that 25 of 20 patients had no peak level before 120 rnin. Epinephrine reduced absorption of diacetylmorphine from the extradural site by at least 55% over the first 30 min. The incidence of patients with more than 9 hr analgesic duration was significantly ( P = 0.033) greater in patients who had diacet!ylmorphine and epinephrine. The use of diacetylmorphine as a model for lipophilic opiates showed that addition of epinephrine not only reduced systemic absorption but also increased analgesic duration. The addition of epinephrine to similarly lipophilic opiates should have the same clinically desirable consequence.

Effect of Extradural Diamorphine on Analgesia After Caesarean Section Under Subarachnoid Block

“…Differences between these two groups were not significant at any time of measurement. By causing vasoconstriction of the extradural veins, adrenaline decreases the amount of diamorphine absorbed systemically [11], thus effectively increasing the concentration available in the extradural space and thus we expected more prolonged analgesia in the women receiving adrenaline. The small numbers in each group may account for why we did not find this.…”

The effect of the addition of adrenaline to pethidine for patient‐controlled epidural analgesia after Caesarean section

“…In our previous study, we found that adding adrenaline to a single dose of epidural pethidine had significant advantages [9]. By producing vasoconstriction in the epidural space, adrenaline is thought to reduce the rate of vascular absorption and enhance transfer of drugs across the dura [11, 12]. Also, stimulation of α 2 ‐adrenoceptors in the spinal cord has a direct analgesic effect [11].…”

Influence of Epinephrine and Medetomidine on Systemic Absorption of Lidocaine Applied Epidurally in Anesthetized Swine

“…Following epidural administration, in order to reach the site of action the local anesthetic needs to cross the spinal meninges [7]. It can either be taken up by the epidural fat, resorbed into the systemic circulation via venous blood vessels, or cross the dura mater and enter the cerebrospinal fl uid [8]. Adrenergic agonists have been frequently combined with local anesthetics to prolong the motor -sensory block through the supposed mechanism of decreasing epidural blood fl ow and by causing antinociceptive effects via interaction with alpha-2-adrenoceptors located in the brain and spinal cord [9][10][11][12][13].…”