Opioid Analgesics

Postoperative pain of moderate or greater intensity should generally be treated with a systemically administered opioid analgesic [1, 5]. The need for analgesia largely depends on the magnitude of the surgical trauma. Generally, the greater the magnitude of surgery, the greater the postoperative discomfort. Major surgery typically requires more aggressive and complex pain management techniques to achieve optimal analgesia. Major surgery usually requires postoperative pain therapy with opioids associated with other drugs, such as oral or parenteral NSAIDs and local anaes-

Table 3. NSAIDs Commonly Used for Postoperative Pain Relief in Adult and Pediatric Patients


Pediatric dosage

Adult dosage


Acetaminophen or Paracetamol

Ibuprofen Naproxen Ketorolac

Acetylsalicylic acid

10-15 mg/kg every 4-5 hr os 20-40 mg/kg every 6 hr rectally or Bolus 20 mg/kg +15 mg/kg every 4 hr os Bolus 40 mg/kg + 20 mg/kg every 6 hr 5-10 mg/kg every 6-8 hr

5 mg/kg every 8-12 hr

10-15 mg/kg every 6-8 hr

200 mg every 3-4 hr os

10 mg every 4-6 hr os

No gastroenteric or hematologic side effects, No antinflogistic effect gastroenteric or hematologic side effects, antinflogistic effect gastroenteric or hematologic side effects, antinflogistic effect Renal and hepatic toxicity

Reye's syndrome (children), gastroenteric or hematologic side effects thetics, administered by different ways (wound infiltration, peripheral nerve block, epidural or iv). Opioids should be used in a multimodal balanced analgesia approach that minimizes opioid requirement and the degree of their side effects [70, 71]. Optimal use of opioid analgesics requires a sound understanding of the general principles of opioid pharmacology, the pharmacological characteristics of each of the commonly used drugs and principles of administration. Fear of potential side effects has limited their use in many countries; this cultural phenomenon seems now to be overcame by the effective opioid titration with the use of incremental doses and a careful monitoring of side effects: this has largely increased their use both in adult patients and especially in children [68, 72]. The mechanism of action of opioid analgesics depends on the interaction of these molecules with specific receptors to which they bind and their intrinsic activity at that receptor [5]. The receptors have a pharmacologic nomenclature: m (1 and 2), d, k. All opioids exert their effects by activating one or more of these receptors. Analgesia involves activation of mu1 receptors in the brain and kappa receptors in the spinal cord. Mu2 receptors are involved in respiratory depression and intestinal constipation. The contribution of delta receptors to analgesia in unclear, and may be more closely related to euphoria. The actions of opioids on receptors can vary depending on the location within the body. For example, a particular opioid may act as an antagonist at the kappa receptors in the brain, but as an agonist at the same type of receptors in the large intestines. Activation of Mu1, Mu2, and delta receptors close potassium channels, while kappa receptors are linked to calcium channels. Humans that have become tolerant to activation of one receptor type are not necessarily tolerant to the others.

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