A nurse is preparing to administer pain medication to a postoperative client who had a total knee replacement and reports pain as 5 on a scale of 0 to 10. Which of the following PRN medications should the nurse plan to administer?

D) Oxycodone causes central nervous system depression: Oxycodone is an opioid analgesic that acts centrally on the central nervous system (CNS) to relieve pain. One of the most significant side effects of opioids like oxycodone is respiratory depression, which occurs due to the suppression of the CNS, particularly in the brainstem respiratory centers. The brainstem regulates respiratory rate and rhythm, and when opioids depress these centers, it can lead to decreased respiratory drive, resulting in a decrease in respiratory rate. A respiratory rate of 8/min is significantly below the normal range, indicating respiratory depression caused by oxycodone.

A) Oxycodone inhibits prostaglandin synthesis: Oxycodone does not directly inhibit prostaglandin synthesis. Prostaglandins are lipid compounds with various physiological effects, including inflammation and pain modulation. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, inhibit prostaglandin synthesis by blocking cyclooxygenase enzymes. However, oxycodone primarily acts on opioid receptors in the CNS to relieve pain, rather than through prostaglandin inhibition.

B) Oxycodone promotes vasodilation of cranial arteries: While opioids can cause peripheral vasodilation, particularly in large doses, the primary mechanism of action of oxycodone is not through the promotion of vasodilation of cranial arteries. Vasodilation may occur as a side effect of opioid use, but it is not the primary cause of respiratory depression associated with oxycodone.

C) Oxycodone blocks the sodium channel suspending nerve conduction: This statement describes the mechanism of action of local anesthetics, such as lidocaine, which block sodium channels to inhibit nerve conduction. However, oxycodone is not a sodium channel blocker. Its analgesic effects result from binding to opioid receptors in the CNS, particularly mu-opioid receptors, rather than blocking sodium channels. Therefore, this option is not the pathophysiology for the respiratory rate of 8/min observed in the client receiving oxycodone.

A) Hematuria: Hematuria, or blood in the urine, is not typically associated with an allergic reaction to cefaclor. Allergic reactions usually manifest with symptoms such as rash, itching, swelling, or difficulty breathing. Hematuria is more likely indicative of a urinary tract infection, kidney stones, or another non-allergic issue.

B) Pruritus: Pruritus, or itching, is a common symptom of an allergic reaction to medications like cefaclor. Itching can occur on the skin or mucous membranes and may be accompanied by other allergic symptoms such as rash, hives, or swelling. Therefore, the presence of pruritus should raise suspicion for a potential allergic reaction to cefaclor.

C) Slurred speech: Slurred speech is not a typical manifestation of an allergic reaction to cefaclor. It is more commonly associated with neurological conditions, intoxication, stroke, or side effects of certain medications, rather than an allergic response to antibiotics.

D) Tremor: Tremor, or involuntary shaking, is not a characteristic sign of an allergic reaction to cefaclor. Tremors can have various causes, including neurological disorders, medication side effects, or metabolic abnormalities. While tremors can occur in severe allergic reactions (anaphylaxis), they are not among the primary symptoms.