Oxycodone is a moderately strong agonist at opioid receptors. These receptors produce analgesic effects through inhibition of calcium influx in presynaptic nerve terminals. Without intracellular calcium, vesicles containing neurotransmitters cannot be released into the synaptic cleft. Additionally, opioid receptor stimulation inhibits potassium efflux from the postsynaptic membrane, thereby further lowering the already negative membrane potential. As a result, much more stimulation is required to generate an action potential.
Oxycodone is indicated for refractory moderate to severe pain. This drug can be used for acute or chronic pain. This should be considered when non-opioid pain medications either fail or are deemed insufficient to achieve adequate pain control.
Due to oxycodone’s inhibitory effect on the medullary respiratory center, it can cause respiratory depression. This could potentially lead to hypoxia, and patients should be advised not to take more than their prescribed dose. Over time, patients will develop a tolerance to this adverse effect.
Constipation is a commonly experienced side effect of opioid analgesics. Inhibition of neuronal action potentials in the enteric plexuses of the GI tract will slow down intestinal motility, leading to increased water reabsorption, hardening of the stool, and constipation. Patients can be given stool softeners concurrently in order to ensure regular bowel movements. Patients will not develop a tolerance to this over time.
CNS Depression is a potential side effect of oxycodone, especially at higher doses. The inhibition of nociceptive neuronal firing is not totally specific and may inhibit neurons globally as well. Patients on higher doses can feel sedated, and should be advised against operating machinery or vehicles.
Opioids have a high potential for addiction and misuse. Their analgesic and sedating effect may be used to cope with unwanted emotions or situations, thus driving a psychological addiction. Over time and with repeated exposure, patients may develop a physical dependence to these medications. Upon cessation of the medication, patients may experience hypersensitivity, agitation, anxiety, excessive lacrimation and sweating, piloerection (cold-turkey) and yawning. Patients should be counseled on the potential consequences of this drug before beginning long-term therapy.
Patients who present with acute opioid toxicity should be administered naloxone. Patients with acute opioid toxicity may present with severe respiratory depression with hypoxia, loss of consciousness, and miosis. Naloxone injection or nasal spray will act immediately to reverse the effects of opioids, sometimes immediately inducing withdrawal symptoms.
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