CLASSIFICATION VS DESCRIPTION OF “PAIN”

Patients won’t refer to the type of pain, only “it hurts”. You must determine if it is inflammatory, traumatic, trauma related, etc. The choice of an analgesic depends on the type of pain; if inflammatory, use a non-steroidal anti-inflammatory analgesic, if its neuropathic, you must use an entire different analgesic. Most dental related pain is traumatic, related to tissue injury.


For many of us, “mild, moderate, severe” is the way we quantitatively identify pain. This is not really adequate to describe pain, it should be based on a more exact scale such as the visual analog scale (VAS) to be described later.


We also must talk about acute vs. chronic pain; acute pain includes a duration of the regimen, many of the drugs we will discuss are approved for “acute pain in adults, no longer than 3-5 days therapy”. Whereas chronic pain lasts day after day, month after month, so managing that kind of pain requires a different strategy. So we must be able to manage the different types of pain.


There are pain patterns involving the central nervous system. The thalamus and CNS are the origin of pain in some cases. Most pain that you’ll see in dentistry is from peripheral origins—something happens to peripheral tissues, mediators are released and activate pain receptors, and the pt perceives the pain via a central mechanism. Some pain is of vascular origin, such as migraine headaches—to treat these we use analgesics that affect vascular tissue. We don’t call anti-migraine drugs analgesics, because they act on the physiology of the vasculature.


Many pts seen in practice or clinic are being treated for arthritis. If a pt is taking a good heavy dose of anti-inflammatory for their arthralgia and come in for a dental procedure, do they already have effective analgesia? The need to prescribe analgesia may be affected when a pt is taking drugs for chronic arthritis.


Evaluating analgesics vs. placebo effects is important. Sometimes a placebo such as a sugar pill (or any pill with no active ingredient) is given during clinical trials to test the effectiveness of an analgesic vs the psychological effects associated with a fake treatment (the placebo). It is unethical for anyone to prescribe a placebo unless you’re doing a study, and in that case you’ve got to get all kinds of clearance from ethics committees, etc.


Pain is mediated by many pathways. Chemical mediators of pain and drug targeting include prostaglandins (PGE1, PGE2), which cause dental pain, inflammation, and fever. There are other mediators that could be effected by a particular drug strategy, but overwhelmingly the peripheral acting agents are modifying the production of theses chemical mediators which precipitate pain.


Pain pathways are well known. Peripheral nerves to the spinal cord to the ascending tracts to the thalamus and ultimately pain is perceived in the sensory cortex (homunculus). The distribution of pain in the sensory cortex is well represented in the neck, tongue and oral cavity. So the central pathway becomes essential and for many patients analgesics must block the central pathway. Remember, blocking a peripheral nerve with lidocaine is not considered analgesia, licocaine is a local anesthetic NOT an analgesic.


There is an emotional aspect of pain, commonly manifested as depression associated with a chronic pain (such as chronic lower back pain). Thus, anti-depressants are common adjuncts in the treatment of long-term pain. The limbic system is the origin of pain’s emotional component.


Approximately 50% of prescription drugs are also available over the counter (otc). A prescription is good if you want to really control the pain because you can prescribe a specific dose, regimen, etc. If a pt calls with residual pain after, for example, an extraction, it’s ok to tell them to just take some ibuprofen or other otc analgesics. There is now some concern about otc drug abuse.


The DEA regulates the classification of narcotic drugs, we’ll say a lot about schedule II, III, and IV analgesics in the future. The typical schedule II analgesics are those that have addiction liabilities (ie. Codeine and morphine). Schedule III and IV are less addictive. There is talk about changing the classification of Vicodin from schedule III to II, because of the potential for abuse. Schedule II drugs need special triplicate forms for prescriptions. Vicodin is one of the most heavily abused drugs in medicine and dentistry and is the number one cause of dentists losing their license for drug “misdirection”, either using it themselves or over-prescribing it.


For therapeutic decision making, the clinician must know the nature and severity of pain, the best indicated class of analgesics, contraindications, doses and dose regimens, and drug interactions.


Although there are a variety of views on the subject, there is no reason to think that former heroin or narcotic users would need a different amount of analgesic. However, former substance abusers may have different levels of tolerance as to local anesthetic administration. These are unresolved issues, however.


There are known drug alternatives for the management of pain, such as acupuncture, hypnosis, etc.

Category: Pharmacology Notes