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Questions – Local Anesthetics and Opioid Analgesics

by Pravin Shukle, MD
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    00:01 Let's move on to local anesthetics and opioid analgesics questions.

    00:05 So, question number 1, the actions of lidocaine are enhanced when, and select the one true statement.

    00:13 Inflammation of the tissues is present, resulting in a drop in the tissue pH to 6.7.

    00:19 B, the nerve being targeted is firing very rapidly. C, blood flow to the lung is reduced.

    00:31 D, blood flow to the target tissue is increased. And E, the patient is hypercalcemic.

    00:39 So, which one enhances lidocaine activity? Right, the answer is B. So remember, that these conditions enhance the activity of local anesthetics.

    00:52 An alkali pH, because as weak bases, the drug need to be less water soluble and more lipid soluble.

    00:59 Rapidly firing nerves will intake the drug more rapidly. Myelinated nerves will intake the drug more rapidly.

    01:07 A reduced blood flow to the tissue will often help the activity of the drug because it's not being carried away.

    01:15 And that's the reason why we co administer a local vasoconstrictor in many cases.

    01:20 And finally, elevated potassium levels and lower calcium levels will enhance the local anesthetic.

    01:27 The question was asking about high calcium levels, and therefore, that works against the opioid analgesic.

    01:35 Okay, the next question. Bone pain in an end stage cancer patient is best treated with, A, fentanyl.

    01:44 B, acetaminophen. C, codeine. D, naloxone. Or E, buprenorphine? Fentanyl, right. So, let's take a look at all of these choices. This patient is an end stage cancer patient.

    02:03 He or she requires potent narcotics. The risk of long term addiction is just not an issue here because the patient is probably not going to survive too long. Fentanyl is the strongest of the opioids that are listed here.

    02:18 In fact, the only opioid that's stronger than fentanyl is Sufenta, which is used in anesthesia.

    02:23 Now, acetaminophen and codeine can be used in combination with fentanyl for mild pain.

    02:29 Naloxone is an antagonist and is used for overdose management. So, it's not really relavent here.

    02:37 And this last drug is a partial agonist and antagonist, and it may have a therapeutic "ceiling", and the other problem is, is that if you have breakthrough pain, you can't really use more opioids, because it's such a tight binder to the mu receptor. So, the real answer here is fentanyl, and we use fentanyl patches or other types of administration of fentanyl to make sure that we control pain in these very unfortunate patients.

    03:03 Question. A patient is brought into the cancer center by his family. He has a history of depression.

    03:09 He was given meperidine for pain management yesterday. He feels hot and dry, and confused. His vitals are as follow.

    03:17 His temperature is 39.5 degree Celcius, or 104 degrees Fahrenheit.

    03:22 The blood pressure is 132/77, and the heart rate is 140. Pick the one true statement.

    03:29 A, the patient is probably on a serotonin specific reuptake inhibitor.

    03:35 B, the patient is probably on a serotonin norepinephrine reuptake inhibitor.

    03:40 C, the patient is probably on a monoamine oxidase inhibitor.

    03:45 D, the patient is probably on a tricyclic antidepressant. And E, the patient is hypercalcemic.

    03:52 Which is the most likely answer? Right. The patient is probably on a monoamine oxidase inhibitor. So, let's go through each of the choices.

    04:04 If you were paying attention, you know that this patient is receiving meperidine, which can be associated with either a hyperpyrexia syndrome, or a serotonin syndrome.

    04:14 So, hyperpyrexia is associated with monoamine oxidase inhibitors, and a serotonin syndrome is associated with one of the serotonin agonists or serotonin specific reuptake inhibitors or a serotonin norepinephrine reuptake inhibitor.

    04:31 Look, the two syndromes are very similar, they're hard to tell apart, but the one thing that you can rely on, is that the patient is not rigid, and is not diaphoretic. Alright, so that's what distinguishes the two.

    04:44 Another clue is that there are two choices for the serotonin syndrome, A and B.

    04:50 And whenever you're given a situation where you have a choice between two similar drugs that are very very similar, and another drug like monoamine oxidase inhibitor which would lead you on a different path, really consider that other path. So the answer here is monoamine oxidase inhibitors or C.

    05:08 Well, that's it. Should you have any questions or concerns, don't be afraid to email us.

    05:12 I know that you're going to do really well on your exams. Good luck.


    About the Lecture

    The lecture Questions – Local Anesthetics and Opioid Analgesics by Pravin Shukle, MD is from the course CNS - Pharmacology.


    Author of lecture Questions – Local Anesthetics and Opioid Analgesics

     Pravin Shukle, MD

    Pravin Shukle, MD


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