Advanced Education In General Dentistry

Module 01: Advanced Pain Control and Sedation

Pharmacology

Narcotic Analgesics

The three commonly used narcotic analgesics include morphine, meperidine and fentanyl. Narcotics act at a variety of opioid receptor sites. The four subclasses of opioid receptor types include the mu, kappa, delta and sigma receptors. Mu and kappa receptors cause respiratory depression and analgesia when they are stimulated. The delta receptor causes changes and affected behavior, and the sigma receptor, when stimulated, causes dysphoria and other limbic system affects.

Morphine

Though morphine is the Ňgold standardÓ of the narcotics, it has many effects. Morphine works at both the Mu and Kappa receptors. In the central nervous system, it causes analgesia, mood changes and drowsiness, respiratory, respiration; it decreases the title volume and the minute ventilation, and it also decreases the responsiveness of the breathing centers of the brain to increasing levels of carbon dioxide. In the cardiovascular system, it will decrease cardiac work and oxygen consumption, which is why morphine is one of the agents administered to patients with acute myocardial infarction.

There are also effects on the G.I. system. It decreases G.I. motility and also increases biliary tract pressure (must be used with caution in patients with pyelocystitis).

Side effects include:

Morphine and other narcotics are absolutely contraindicated in patients who are on MAO inhibitors. Dosage: 2 to 10 mg IV or subcutaneous. (Administering an IV takes affect within seven minutes, and the patient must be monitored post administration). The half life of morphine is approximately two to three hours and should be limited to procadium lasting more than two hours.

Meperidine

Meperidine is one tenth as potent as morphine, however, in equi-analgesic dosages, the same effects are seen and the same side effects are seen, including histamine release and apnea. Nausea and vomiting are also a troubling side effect, and frequently fenergin is administered in combination with meperidine when it is used as a post-operative analgesic. Again, merperidine is absolutely contraindicated in patients on MAO inhibitors. Meperidine has atropine-like properties, it will decrease salivary secretions and increase heart rate second to vagolytic activity.

Dosage: 25 to 75 milligrams IV or IM. Onset 2-4 min of action. Duration 30-45 minutes.

Adverse Reactions:

Fentanyl

Fentanyl is 80 times more potent than morphine. Its duration of action is much shorter, lasting about 45 minutes, and it is therefore generally not used as an analgesic for post-operative pain. It can cause respiratory depression and, if administered too rapidly and in higher dosages, it can also cause chest wall rigidity. An advantage to fentanyl is that there is minimal histamine release with this agent, and it is well tolerated by asthmatics.

Dosage: 25 to 100 µg IV. Again, fetanyl, like other narcotics, must be administered with caution to patients with COPD.