Respiratory depression, with morphine

The use of opioids in very young patients is increasing. In a review of pain management in children, various routes of administration of opioids and their associated adverse effects have been discussed (SEDA-17, 78). Attention has been drawn to the adverse effects of intravenous codeine in children and to the risk of convulsions with pethidine in neonates, because of accumulation of its metabolite norpethidine. The risk of respiratory depression with morphine was also highlighted, and morphine is recommended for use only in neonates who are being ventilated or intensively nursed. Routine use of pulse oximetry has been recommended in all children receiving opioids (SEDA-21, 86). 

Konieczko KM, Jones JG, Barrowcliffe MP, Jordan C, Altman DG. Antagonism of morphine-induced respiratory depression with nalmefene. Br J Anaesth 1988 61(3) 318-23. 

The use of patient-controlled analgesia (PCA) (SEDA-15, 68) highlights the importance of adequate monitoring, in order to avoid potentially catastrophic adverse effects, such as respiratory depression. With PCA, patients generally use less morphine but still achieve the same degree of pain control (7). This supports the view that selfadministration of opioids does not put patients at risk of over-medication or drug dependence. 

Although associated with less respiratory depression than morphine at recommended doses, tramadol has a side-effect profile that in some ways is similar to that of the previously mentioned opioid analgesics (e.g., dizziness, euphoria, hallucinations, cognitive dysfunction, and constipation). Tramadol alone may enhance the risk of seizures. In addition, concomitant use with serotonin reuptake... 

Ketamine is a respiratory depressant like morphine, but less potent, and its effects can be additive with morphine. The manufacturer notes that prolonged recovery time may occur if opioids are used with ketamine. ... 

The existence of further alternative transcripts of MOP was postulated by the observation that in knockout mice with disrupted exon 1, heroin but not morphine was still analgesically active. Based on earlier observations that the antagonist naloxazone blocked morphine-induced antinociception but not morphine-induced respiratory depression, a subdivision of the MOP in pi and p2 was proposed. However, no discrete mRNA for each of these MOP subtypes has been found. It is, however, possible that subtypes of MOPs result from heterodimerization with other opioid receptors or by interaction with other proteins. 

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. 

Major gastrointestinal effects include decreased gut motility and changes in secretion of gastric and intestinal fluids. Morphine and most p receptor agonists cause pupillary constriction. Some tolerance to this effect may develop, but addicts with high opioid levels will still have miosis. Respiratory depression is the usual cause of death from opioid overdose. 

The history of this class of analgesics might have stopped there were it not for the manifold ancillary activities shown by that molecule. Although still one of the most widely used agents for treatment of severe pain, morphine is a drug that must be used with caution. Side effects include respiratory depression, induction of constipation, and sometimes marked sedation. The one property that most severely limits use of this drug is its propensity to induce physical dependence in patients subjected to more than casual exposure. 

The answer is c. (Hardman, pp 528-537.) Morphine is a pure agonist opioid drug with agonist activity toward all the opioid subtype receptor sites. In high doses, deaths associated with morphine are related to the depression of the respiratory center in the medulla. Morphine has a high addiction potential related to the activity of heroin or dihydromorphine. Codeine has a significantly lower addiction potential. 

This class produces analgesia and has a ceiling effect on respiratory depression and lower abuse potential than morphine. However, psychotomimetic responses (e.g., hallucinations and dysphoria with pentazocine), a ceiling analgesic effect, and the propensity to initiate withdrawal in opioid-dependent patients have limited their widespread use. 

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