Which of the following is a serious adverse reaction associated with Demerol?

Severe respiratory depression is a well-documented and serious adverse reaction associated with Demerol (meperidine), an opioid analgesic. Opioids work by binding to the mu-opioid receptors in the brain, which can effectively relieve pain but also depress the central nervous system functions, including the respiratory drive. This effect can lead to reduced breathing rates and inadequate oxygenation, which can be life-threatening.

When administering Demerol, especially in cases where the dosage is high or in patients who are opioid-naïve, providers must closely monitor respiratory status. Other factors, like concurrent use of other depressants, could further exacerbate this risk, making it important for healthcare professionals to be vigilant.

The other options, while they might be associated with various medications or conditions, do not present the same level of immediate danger as severe respiratory depression related to opioid use. Headache, dry skin, and weight gain, while they can occur as side effects or associated symptoms, do not have the same critical implications regarding patient safety as respiratory depression does.