Fentanyl: Transdermal, Transmucosal, Epidural, and Overdose Risks
Transdermal Fentanyl: Risk of Respiratory Depression
Why do we say that once a transdermal fentanyl patch is removed, the patient is still at risk of respiratory depression? How long does it persist?
Fentanyl forms a depot in the connective tissue of the skin, which continues to release the drug for approximately 17 hours after patch removal. The risk of respiratory depression persists for up to 24 hours after stopping treatment, so continued monitoring is essential.
Disadvantages of Transdermal Fentanyl Administration
- Poor analgesic coverage during the first 12 hours of therapy.
- Persistent increased risk of respiratory depression.
- Increased rate of drug absorption with elevated body temperature (fever) or environmental temperature (avoid saunas, for example).
How a Fentanyl Patch Works
The patch contains a drug reservoir and a membrane that releases the drug at a constant rate. It can take 4 to 12 hours for the effect to begin, reaching peak plasma concentrations at 14 hours, and its effect lasts about 17 hours.
Transmucosal Oral Administration of Fentanyl
This is a presentation of the drug in the form of a lozenge (“lollipop”) that can be sucked. Approximately 25% of the fentanyl is immediately absorbed through the oral mucosa, leading to rapid therapeutic plasma concentrations. The remaining 75% is absorbed more slowly through the stomach.
Opiate Overdose: Risk of Respiratory Depression After Naloxone
In the context of an opiate overdose, why does the risk of respiratory depression remain after naloxone administration, even if the overdose has been reversed?
Because naloxone has a shorter half-life than many opioids, there is a possibility that the person who overdosed may experience respiratory depression again when naloxone concentrations in the blood decrease, while toxic concentrations of the opioid persist.
Epidural Fentanyl: Rapid Onset of Effect
Why does fentanyl, when administered epidurally, have a very rapid onset of effect?
Because it goes directly to the target organs without passing through barriers or the hepatic first-pass effect.
Potential Complications in a Trauma Patient with Altered Consciousness
You are caring for a multiple trauma patient with a head injury, who has a greatly diminished level of consciousness (only opens their eyes to powerful stimuli), is receiving a high-chloride parenteral nutrition, and has continuous enteral feeding through a nasogastric tube. What are the potential complications?
- Risk of respiratory complications due to mucus secretion caused by immobility or inability of the tongue to manage secretions.
- Delayed gastric emptying, increasing the risk of regurgitation.
- If gastric residual volume is greater than 150 ml, there is an increased risk of aspiration.
- Risk related to a closed cardia.
Risk of Bleeding and Peptic Ulcer with NSAIDs
Why do the majority of nonsteroidal anti-inflammatory drugs (NSAIDs) cause a risk of bleeding and peptic ulcer disease?
Because they inhibit the enzyme cyclooxygenase-1 (COX-1).
Main Clinical Effects of NSAIDs
- Analgesic Action: The analgesic effect is largely a peripheral effect due to the inhibition of prostaglandin synthesis at the site of pain and inflammation.
- Anti-inflammatory Action: Prostaglandins cause vasodilation, increased permeability, and edema during inflammation. NSAIDs reduce these effects.
- Antipyretic Action: In fever, leukocytes release inflammatory pyrogens, a phenomenon that is part of the immune response. These substances act on the hypothalamus’s thermoregulatory center, causing an increase in body temperature. NSAIDs reduce fever by inhibiting prostaglandin synthesis.