Narcotic Analgesics Flashcards
What are the endogenous opioids? What other things do they share a common precursor with?
- endorphins
- common precursor with ACTH (stress analgesia), MSH, b-LPH
Where in the body can opioid receptors be found?
- brain, spinal cord, peripheral nerves
What kind of receptors are opioid receptors? What are their major downstream effects?
- GPCR (MOR most important for analgesia)
- inhibits adenylyl cyclase
What is the major theory behind the development of tolerance in opioid users?
- receptor internalization (may also involve phosphorylation)
What two organs need to be functional to acheive proper pharmacokinetics of narcotics?
- conjugated in LIVER with glucuronic acid
- excreted by KIDNEY
You dose a narcotic to a patient on the floor. When you check back 30 mins later, the patient is sleepy and without pain. You schedule the next dose for 4 hours later. However, you get paged 1 hour later and the nurse says the patient is in excruciating pain. You hadn’t expected the opiate to wear off this quickly. What happened and what do you do?
- bolus effect (swings in plasma concentration)
- switch to extended release or continuous IV
WHO has a 3-step pain ladder. What drugs are in each category (mild, moderate, and severe)?
1) Mild - ASA, acetaminophen, NSAIDS
2) Moderate - A/codeine, A/hydrocodone, A/oxycodone, A/dihydrocodeine, Tramadol
3) Severe - Morphine, hydromorphone, methadone, levorphanol, fentanyl, oxycodone
Which metabolite of morphine is more active and has a higher potency?
- morphine-6-glucuronide
How does codeine work, and absence of what enzyme will lead to side effects with no pain relief?
- converted to morphine
- CYP2D6 is essential for conversion and absence occurs in 10% of Caucasians
Tramadol is a weak mu agonist. What other actions impact the analgesic quality?
- inhibition of NE and 5HT uptake
This opiate is very potent, has a very long half life, is applied via a patch, and is lipid soluble. Since there is delayed toxicity, you must wait one week between changing doses.
Fentanyl
This drug has an extended duration of action, is mostly bound to plasma proteins, can gradually accumulate in tissues, and is often used to treat heroin users. Also where Tobias goes to improve his method acting.
Methadone
Why is meperidine no longer used? What are its congeners, and what are these drugs used for?
- has toxic metabolite (normeperidine)
- interacts with other medications and can cause serotonin syndrome
- Congeners: diphenoxylate and loperamide, used to treat diarrhea
Which opioid antagonist is used for treatment of opioid overdose and which opioid antagonist is used for treatment of alcoholism?
- OD: naloxone
- alcoholism: naltrexone
You’re on the rehab floor. A patient recovering from a femur fracture is managing their pain well with 10 mg of oxycodone every 4 hours. Their PT approaches you and says that the same patient couldn’t participate in rehab earlier because of severe limiting pain. What’s your plan of attack (drug and dose)?
- breakthrough dosing! Used when patient can anticipate that their pain will be exacerbated
- use same drug in immediate release form at 10% of total 24 hr dose
- i.e. in this patient, you would administer 6 mg oxycodone ~30 mins before scheduled PT
