Administer a cleansing enema — This is correct because the provider prescribed a hypertonic cleansing enema to relieve the opioid-induced constipation, and the abdominal x-ray confirmed no obstruction, making enema safe and appropriate.

Assist the client to a left side-lying position with the right knee flexed — This is correct because this is the optimal position for enema administration, allowing solution flow into the rectum and sigmoid colon.

Prepare the client for a chest x-ray — Not indicated, as there are no respiratory concerns.

Auscultate bowel sounds — While part of general GI assessment, bowel sounds were already assessed with imaging; this is not the immediate next step before enema administration.

Perform a manual digital rectal exam — Not indicated unless fecal impaction is strongly suspected; the provider did not order this, and the x-ray shows stool throughout the colon, not just rectal impaction.

Administer oxycodone extended-release tablets — This would worsen constipation and is contraindicated in the context of severe constipation.