By Adem Lewis /

This basic pharmacology video will
review pain medication. I’d like to briefly explain what happens when we have pain to help you understand how some of these medications work. So, I hit my thumb with a hammer. The pain receptors called nociceptors in my thumb
release a chemical called arachidonic acid. Now meanwhile in my body there are enzymes cyclooxygenase or COX for short. These enzymes are all over our bodies
and they do many functions. One job of COX-1 is to help maintain the normal lining of the stomach. It is also involved with kidney and platelet function. COX-2
is present at sites of inflammation. Cox-2 is present at sites of inflammation Now, back to the hammer. With that painful stimulus, Cox and arachidonic acid combine and they create a chemical
called prostaglandin. Prostaglandins when these prostaglandins are made three things happen. I have pain inflammation and fever. So does it make sense that medications would be made to target COX which would in turn ,Interfere with prostaglandin production, which in turn would relieve pain, inflammation, and fever? NSAIDS stand for non-steroidal anti-inflammatory drugs. These medications decrease inflammation, but they’re not a steroid. NSAIDS also
relieve pain and fever. They work by inhibiting COX-1 and COX-2, which
inhibits prostaglandin synthesis. Examples of NSAIDS include ibuprofen,
brand name Motrin or Advil, naproxen or Naprosyn, salicylic acid or aspirin, and ketolac, brand name Toradol. Ketorolac is interesting that it can be given not only PO but IM and IV. Many times NSAIDs are combined with narcotic analgesics for pain relief. They work synergistically together to create a great analgesic effect with a lower narcotic dose. Remember that one of COX-1 jobs is to maintain the stomach lining, so does it make sense that inhibiting this medication would cause gastric upset, and potentially ulcers, and gastrointestinal bleeding? Individuals on NSAIDS should be
assessed for increased bleeding, bleeding gums or bleeding may be noted, more
bruising or bleeding in the urine or the stool. Taking NSAIDS with food or with a
full glass of water or milk may decrease that gastric irritation. Drowsiness, headache, constipation, and rash are also side effects. Because prostaglandins also play a part in maintaining renal blood flow in the kidneys blocking prostaglandin can lead to hypertension, renal damage, and even cardiac damage . When NSAIDs are used long-term. If you have asthma and are aspirin
sensitive, using these products may cause severe bronchospasm which can be
life-threatening. Salicylic acid or aspirin is considered
an NSAID but I’ve listed this separately because of some really special
considerations. Again it blocks COX-1 andCOX-2 which inhibits prostaglandin
synthesis. Aspirin is used as an analgesic for pain. It can be an antipyretic for fever, and anti-inflammatory, but it also has an anti- platelet effect and is frequently used to decrease the chance of blood clots in individuals who’ve had, or at risk for heart attacks and strokes. A low dose aspirin of 81 milligrams may be recommended or a regular adult dose of 325 milligrams may be ordered. Excuse me. if you see aspirin 81 milligrams ordered for an adult it’s probably that it’s used for an antiplatelet effect, not for pain control. It makes sense that care must be taken not to combine NSAIDs with other anticoagulant medications. Since COX- 1 is inhibited, again watch the patient for GI upset and GI bleed. Renal and liver damage can occur with long-term use. Aspirin toxicity, the signs of this are tinnitus or ringing in the ear, headache, and confusion. Aspirin can also be added to
narcotics for pain relief, and lastly, aspirin is not recommended for children because of the potential of Reye’s syndrome. some people call that Reyes
Syndrome. So Reyes Syndrome is a rare, but it’s a really serious condition that causes swelling of the liver and severe increase of pressure in the brain. Unless it’s diagnosed and treated, death is common often within a few days. Reyes syndrome most often affects children and teenagers recovering from a viral infection, most commonly the flu or chickenpox. Research has established a link between Reyes Syndrome and the use of aspirin and salicylate containing products. You would be surprised to know that many products besides the aspirin contains salicylates. Some of these products may include sunscreens, products used for acne, bath products, deodorants, dental products like toothpaste and mouthwash, hair products, skin moisturizers, and soaps. COX-2 inhibitors are technically an NSAID because they decrease the production of prostaglandin but these medications only block Cox-2 allowing the COX-1 enzyme to continue to be produced to provide protection to the stomach. This decreases the risk of ulceration and bleeding, so you shouldn’t see any bleeding with individuals who take this. But, risks of heart problems such as MI, heart attack, and stroke can happen. Celecoxib or Celebrex is an example. Because of the structural makeup of this medication celecoxib is contraindicated for use in patients who have demonstrated allergic reactions to sulfa. Acetaminophen decreases pain and fever, but does not have an anti-inflammatory effect. Its exact mechanism of action is unknown. It’s quite the controversy. It may reduce the production of prostaglandins That’s what some of the research says. Some say that it may be more centrally acting in the central nervous system. Acetaminophen is contained in many combination products there we go, such as cold products. So you need to read your labels on those OTC medications. Acetaminophen is also combined with narcotics to treat moderate to severe pain. Combination narcotics will end in “cet” like percocet
or roxicet. Oxycodone with acetaminophen is brand name Norco and Vicodin contains acetaminophen and the narcotic hydrocodone. Side effects of acetaminophen include headache and nausea. Liver damage is the most serious adverse affect. It can be fatal. ,Acetaminophen, how this goes, is that it’s broken down in the liver and it creates several byproducts. These byproducts they don’t hurt us, but if acetaminophen builds up in the liver the pathway that eliminates these are overloaded. Then the liver must use another path to remove these byproducts. When this happens, a toxic compound called NAPQI is made and that causes liver damage! The maximum dose of acetaminophen is 3 grams. Acetylcysteine is the antidote for acetaminophen toxicity. Opioid analgesics also called narcotics are our strongest painkillers. It’s important to note that they don’t do anything at the site of the damaged tissue to reduce the cause of pain. Opioid analgesics, they depress the nervous system and work by binding to opioid receptors which are found in the brain, the spinal cord, peripheral neurons, and the digestive tract. You may say that these medications don’t actually kill the pain but they rather, they block the pain signals to the brain altering our perception of pain. There are 3 different types of opioid receptors and depending on which receptors they bind to, this will vary the degree of effects like sedation, or respiratory depression, and hallucinations. When you hear about medications being opioid agonist antagonist, that just means that they activate some of these receptors and some they don’t. Butorphanol or Stadol is an example of an opioid agonist/antagonist. The active ingredient in most narcotics is opium from the poppy plant or a similar synthetic chemical. Morphine, codeine, and fentanyl are commonly used opioids and our schedule II narcotics which means they have a high potential for addiction. Of course, tolerance and withdrawal can also happen with long-term use. Opioids are high alert medication. So care must be taken with administration. Remember, that with any medication that depresses the central nervous system, you must watch for more serious side effects and caution must be taken when given with other CNS depressants. I use the mnemonic A, B, C, D to remember the side effect/ adverse effects of opioids. A is for apnea or absence of breathing. Respiratory depression is a serious adverse effect of opioids. B is for bradycardia. Also watch the blood pressure because hypotension can occur. C is for constipation. When opioids bind to the opioid receptors in the intestine, peristalsis slows down so constipation can occur. There are three D’s: dysphoria, dyspepsia, and dysuria. Dysphoria is a feeling, unpleasant or a restless feeling. Dyspepsia is an upset stomach. Of course nausea and vomiting are common side effects of opioids. Lastly D is for dysuria. These medications can cause urinary retention. As we consider these side-effects, it makes sense that you would want to assess vital signs including oxygen saturation prior to administration. ,Because of the CNS depression drowsiness can occur putting the patient at risk for falls. We must also assess for constipation and urinary output. Naloxone is the antidote for opioid overdose. I wanted to put tramadol in here because this is a very interesting drug. It’s known as a centrally acting analgesic. It binds to the MU opioid receptors, but it has a weaker effect. It also inhibits the neurotransmitter serotonin and norepinephrine which decrease the pain signal transmission to brain sites that perceive pain. Tramadol is considered to have a low potential for
dependence relative no morphine, but dependence may occur with prolonged use and it’s classified as a schedule IV controlled substance. Tramadol produces opioid like effects both mentally and physically but these effects, they’re mild and they’re not produced following parental administration. Overdose can cause respiratory depression and seizures. Naloxone may reverse some but not all of the symptoms of tramadol overdose. Well that concludes this lecture on pain medication. Let me know if you have any questions.

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