Epidural administration route

Morphine may be administered orally, intravenously, or epidurally. An advantage of epidural administration is that it provides effective analgesia while minimizing the central depressant effects associated with systemic administration. The mechanism of action with the epidural route of administration involves opioid receptors on the cell bodies of first-order sensory neurons in the dorsal root ganglia as well as their axon terminals in the dorsal hom. Stimulation of these receptors inhibits release of substance P and interrupts transmission of the pain signal to the second-order sensory neuron. 

Side effects and complications tend to be higher with the intrathecal than the epidural route. A common side effect is pruritus, the incidence of which is higher with intrathecal than with epidural administration. It is dose-dependent, with an incidence of about 10% after epidural morphine 5 mg. The risk of severe, distressing itching is about 1%. Pruritus may be related to cephalad spread of morphine... 

The adverse effects reported with epidural administration are similar to those reported with the intrathecal route. Again, old age and respiratory disease probably dispose to respiratory depression (133). As can be predicted from pharmacokinetic considerations, delayed respiratory depression is more common with epidural morphine than with fentanyl (134). 

Rarely, adverse events are reported when an apparently innocuous formulation is administered by the wrong route. Usually these problems arise because of excipients that the typical physician takes little interest in. Intravenous remifentanil is formulated with glycine, and hence it is not well-suited for epidural administration. 

Drug administration route Patient-controlled epidural analgesia with bupivacaine 0.06% and hydromorphone 10 micrograms/ml in postoperative 3736 orthopedic patients was associated with nausea (30%), pruritus (15%), hypotension (10%), and sedation (0.08%) [105. Respiratory depression was not reported, and Acre were no epidural hematomas or abscesses. 

Fig. 13.2 Epidural and intrathecal administration route. Source Recepteerkunde 2009, KNMP...

An example of calculating the limits for endotoxins A morphine containing injection solution with the strength of 100 mg/5 mL has been prepared. Because the product will be administered parenterally a bacterial endotoxins test has to be performed. Therefore the administration route has to be known is this intravenous or intrathecal or epidural. For endotoxins in intravenous administration the requirement is maximally 5 EU/kg body weight during 1 h. Based on a body weight of 70 kg this means 350 EU/h. Secondly the maximal dose (in volume of the product per hour) will determine the actual limit. This depends on the need of the patient as well. If he needs the full 5 mL, this makes the requirement for the product to be 350 EU/5 mL = 70 EU/mL. 

This type of pain management is used for postoperative pain, labor pain, and cancer pain. The most serious adverse reaction associated with the administration of narcotics by the epidural route is respiratory depression. The patient may also experience sedation, confusion, nausea, pruritus, or urinary retention. Fentanyl is increasingly used as an alternative to morphine sulfate because patients experience fewer adverse reactions. 

Opioids maybe administered in a variety of routes including oral (tablet and liquid), sublingual, rectal, transdermal, transmucosal, intravenous, subcutaneous, and intraspinal. While the oral and transdermal routes are most common, the method of administration is based on patient needs (severity of pain) and characteristics (swallowing difficulty and preference). Oral opioids have an onset of effect of 45 minutes, so intravenous or subcutaneous administration maybe preferred if more rapid relief is desired. Intramuscular injections are not recommended because of pain at the injection site and wide fluctuations in drug absorption and peak plasma concentrations achieved. More invasive routes of administration such as PCA and intraspinal (epidural and intrathecal) are primarily used postoperatively, but may also be used in refractory chronic pain situations. PCA delivers a self-administered dose via an infusion pump with a preprogrammed dose, minimum dosing interval, and maximum hourly dose. Morphine, fentanyl, and hydromorphone are commonly administered via PCA pumps by the intravenous route, but less frequently by the subcutaneous or epidural route. 

Morphine is often the choice in this category (1) multiple products available (2) multiple route of administration options, such as oral, rectal. IM. SC. IV. epidural, and intrathecal and (3) a known eqiipotency between these routes that allows a much easier transition. 

Astromorph PF, Duramorph, Infumorph - Because of the risk of severe adverse effects when the epidural or intrathecal route of administration is employed, patients must be observed in a fully equipped and staffed environment for at least 24 hours after the initial dose. 

Dosages and routes of administration Morphine is available in different salt forms but the hydrochloride and sulfate (Vermeire and Remon, 1999) are used preferentially. The compound can be administered by the oral, parenteral or intraspinal route. Oral application is preferred for chronic pain treatment and various slow release forms have been developed to reduce the administration frequency to 2-3 times per day (Bourke et al., 2000). Parenteral morphine is used in intravenous or intramuscular doses of 10 mg, mostly for postoperative pain and self-administration devices are available for patient-controlled analgesia (PCA). Morphine is additionally used for intraspinal (epidural or intrathecal) administration. Morphine is absorbed reasonably well in the lower gastrointestinal tract and can be given as suppositories. 

Dosages and routes of administration Sufentanil is mostly given parenterally as an intravenous bolus or as brief injection or infusion during anesthesia. For pain treatment, intravenous or epidural on-demand procedures are in use. Doses up to 8 pg/kg are adequate for pain treatment and higher doses up to 30 pg/kg for surgery (Grass, 1992). 

Opioid analgesics can also be used at low doses by the epidural and spinal routes of administration to produce excellent postoperative analgesia. 

Patients with cholestatic conditions such as gallstones, primary sclerosing cholangitis or Alagille s syndrome often suffer from pruritus that can be extremely debilitating. In such patients it would seem sensible to avoid medication that could exacerbate this symptom. Administration of opiates via the intrathecal and epidural routes lead to a high incidence of pruritus (up to 80% with epidural morphine) [2]. 

Other routes of administration used by specialists are epidural (obstetrics) and intrathecal (see p. 360) very low doses are used. 

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