Which medication requires caution if morphine has already been administered?

Fentanyl, also known as oral transmucosal fentanyl citrate (OTFC), is a potent opioid analgesic that can lead to increased risk of respiratory depression when administered in conjunction with other opioids like morphine. When morphine has already been given, adding fentanyl increases the cumulative effect of opioids on the central nervous system. This can lead to heightened side effects such as sedation and respiratory depression, making it essential to exercise caution.

In contrast, medications like ibuprofen, acetaminophen, and aspirin are non-opioid analgesics and do not carry the same risk of respiratory depression when administered after morphine. They work through different mechanisms, primarily focusing on reducing inflammation and pain rather than directly affecting the opioid receptors that are impacted by morphine and fentanyl. Therefore, while they can be used safely in conjunction with morphine for added pain relief, fentanyl's opioid nature necessitates careful consideration.