Opioid pupillary effects

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. 

Pharmacology Nalmefene, an opioid antagonist, is a 6-methylene analog of naltrexone. Nalmefene prevents or reverses the effects of opioids, including respiratory depression, sedation, and hypotension. Nalmefene has no opioid agonist activity it does not produce respiratory depression, psychotomimetic effects or pupillary constriction, and no pharmacological activity was observed when it was administered in the absence of opioid agonists. Nalmefene can produce acute withdrawal symptoms in individuals who are opioid-dependent. 

Miosis, or the pinpoint pupillary response to the opioids, is diagnostic of the use and abuse of the opioids. No tolerance to such an effect is observed. Miosis is due to disinhibition of the Edinger-Westphal nucleus in the cortex resulting in increased pupillary constrictor tone. 

Peak respiratory depression is observed within 1 hour of intramuscular administration, and there is a return toward normal starting in about 2 hours. Like other opioids, meperidine causes pupillary constriction, increases the sensitivity of the labyrinthine apparatus, and has effects on the secretion of pituitary hormones similar to those of morphine. Meperidine sometimes causes CNS excitation, characterized by tremors, muscle twitches, and seizures these effects are due largely to accumulation of a metabolite, normeperidine. As with morphine, respiratory depression is responsible for an accumulation of CO2 which, in turn, leads to cerebrovascular dilation, increased cerebral blood flow, and elevation of cerebrospinal fluid pressure. 

Miosis Pupillary constriction is a characteristic effect of all opioids except meperidine, which has a muscarinic blocking action. 

It has been adequately proved based on the available evidence that naloxone specifically antagonizes the opioid effects, such as respiratory depression, psychotomimetic effects, and pupillary constriction, by means of genuine competition for the receptor sites. The drug disappears from serum in man in a much rapid fashion. After an IV administration it is distributed quite rapidly in the body. It is found that the biological half-life in adults ranges between 30 to 81 minutes whereas, the mean half-life in neonates is 3.1 and 0.5 hour. 

Despite the increases seen in loperamide plasma levels seen in both studies with ritonavir alone, a lack of central opioid effects with loperamide (such as pupillary constriction, respiratory depression and also analgesic effects) was demonstrated. This suggests that the combination of loperamide with... 

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