Opioid analgesics

Major drugs: Morphine, Methadone, Meperidine, Fentanyl, Butorphanol, Pentazocine… none of these drugs are commonly used in dentistry! So its kind of a misrepresentation of what’s important to you as practitioners, so we’ll look at a different set of drugs. The narcotic class, which also includes all of the opioids and opiates are used to relieve moderate to severe pain- this is controversial because the Cox-2 inhibitors (Vioxx and Celebrex) are also indicated for moderate to severe acute pain. The COX-2 inhibitors are of the non-inflammatory class (NSAIDs) yet have the same therapeutic window as the narcotics. This is important, because when you’re dealing with pain and you can’t characterize it as mild, moderate or severe, its always best to see if the pt will respond to an NSAID. But for some reason, in dentistry, regardless of the nature of the pain, pts are being given prescriptions for Vicodin (which is an acetominophen, hydrocodone preparation) or Tylenol III (which is acetominophen plus codeine). Your options are much greater than that! So moderate to severe pain is really the indication for the opioid analgesics, not mild pain.


These drugs are also used in medicine to control diarrhea because there are opiate receptors in the gut and if you occupy those receptors you can reduce peristalsis, such drugs are usually used acutely (we’ll cover these in later lectures). Cough suppression; many of the otc agents have opiate like action on the cough center in the medulla oblongata, and that’s a reasonable strategy but these have nothing to do with analgesia.


More and more we’re seeing this in the clinic, a pt could be on a maintenance dose of methadone, this is an oral opiate analgesic- 400mg/day, because he’s a former heroin addict and he’s now taking this maintenance opiate therapy, this is really a massive dose of methadone and has importance as to how you will manage the patient.


Analgesic is defined as a drug that relieves pain without impairing sensory modality. The reality is that the ideal analgesia doesn’t exist because of all the central acting analgesics carry the same warning, they cause sedation and drowsiness and obviously affect sensory modality. We must be careful after prescribing such a drug and sending them on their way to drive an automobile because their motor sensory functions will be impaired; sedation and drowsiness.


The word “narcotic” goes back to 1914 federal legislation, and is defined as a drug that produces a stupor or sleeplike state. Narcotics include opium derivatives, called opiates, derived from the opium poppy (the codeines, the morphines, the heroins). The synthetic ones are called opioids. The words are used interchangeably, however.


Now what do our esteemed authorities at the ADA in Chicago advise dentists with regard to managing their patients? “Because the pain commonly encountered in dental practice is of the acute type, tolerance of, and physical and psychological dependence on opioids are so rare as to be of little concern… The dentist should use opioid medications in sufficiently large doses for high quality management of acute pain without fear that patients will develop dependence. The one exception may be patients with a history of drug abuse. For these patients, nonopioid analgesics or perhaps an agonist-antagonist opioid should be prescribed initially.”


There are many physicians and dentists who abuse, for instance, Vicodin- they over prescribe it and the DEA gets after them. How many doses, and at what dose-level becomes an issue. The one exception with regard to prescribing opiates is when a pt has a history of drug abuse, particularly heroin; do these pts have a vulnerability to a codeine or a Vicodin with hydrocodone in it. Probably you will not precipitate drug seeking behavior, but a lot of the faculty will advise you not to give these former drug abusers a narcotic- go to another agent. The literature is not very supportive of this, there is not any really strong evidence that you’ll induce a renewed craving for heroin but its an issue that you’ll hear discussed by the faculty.


The tri-cyclic anti-depressants, which are used as adjuncts in the management of chronic, particularly neuropathic pain, have nothing to do with opiate receptors. These act instead on norepinephrine re-uptake at the pre-synaptic terminal.


The opiate receptors exist in the CNS on neurons, they are membrane receptors, and the most important one is the “mu receptor”. It is the mu receptor that mediates almost all of the therapeutic effects of the opiate agents.

Category: Pharmacology Notes