Analgesia (2) Flashcards
What are the major opiate antagonists?
Naloxone, naltrexone, and methylnaltrexone
What receptors do Naloxone, naltrexone, and methylnaltrexone work at?
all 3- mu, kappa, and delta (they precipitate withdrawal syndrome in dependent pts., except methylnaltrexone b/c it does not easily pass the BBB(mitigates AEs without impacting (central) analgesia))
What drug is most often used to tx acute opiod OD and to mitigate opiate AEs?
Naloxone IV (may be co-formulated with agonist to prevent drug abuse) (note there is no effect if taken orally, and antagonist action if injected)
What is the main use of maltrexone?
used in maintenance programs for addicts (as a single PO dose on alternative days to decrease alcohol craving, and decrease baseline B-endorphin release)
How would phsyical exam of someone experiencing withdrawal appear?
agitation, diaphoresis, increased lacrimation, piloerection, and dilated pupils
How might alcohol and sedative-hypnotic withdrawal appear?
seizures, hyperthermia, HTN, or tachycardia
How might opiate withdrawal appear?
pulse and BP WNL (usually)
slight tachycardia reflects agitation, discomfort, or hypovolemia
How might sympathomimetic intoxication present?
mydriasis, agitation, tachycardia, and HTN, but usually much more severe than occurs in opiod withdrawal
How might cholinergic agent intoxication present?
diarrhea and vomiting
distinguished from opiod withdrawal syndrome by salivation, bradycardia, and altered level of consciousness
How should shor-term tx of opiate withdrawal be handled?
How addictive are opiates?
as addictive as nicotine, but less than cocaine or amphetamines.
What is thought to underlie addiction/dependence for most drugs?
increase in dopamine levels. For ex., activation of opiate receptors in the ventral tegmental neurons leads to increased dopaminergic activation within the nucleus accumbens
How should opiod dependence be tx?
1) Use of an opiate antagonist such as naltrexone
2) or pts receive a long-acting opiod whose pharmacokinetic properites give rise to only a gradual decline in serum and therefore drug levels, such as buprenorphine
What is the tx of choice for opiod-dependent pregnant women?
Methadone (dose requirements may increase during the 3rd trimester due to larger plasma volume, reduced protein binding, increased tissue binding, and increased metabolism)
What are the AEs of Methadone?
constipation, mild drowsiness, excess sweating, peripheral edema
reduced testosterone leading to reduced libido and sexual performance, and erectile dysfunction
prolonged QT and arrhythmia
What are some main features of buprenorphine?
- very tight binding to opiod receptors (displaces other opiods and triggers withdrawal in pts psychically dependent on opiods; blocks the analgesic action of other opiods)
- slow dissociation from opiod receptors (long DOA and relieves withdrawal and cravings for 24+hr)
- no bioaccumulation (allows quick titration to effective dose)
- partial agonist with ceiling effect (very low risk of OD, might be less effective than higher doses of methadone)
- SL and IV absorption; poor PO absorption (can be abused IV)
In the ED, suspiciion that a pt in toxicated with an opiate (morphine, heroin, codeine, and hydrocodone- wont work for synthetic opiates like fentanyl, meperidine, and methadone) can be rapidly confirmed by what?
antibody-based enzymatic immunoassay (however, the precise conc and pattern of opiate metabolites requires the use of GC-mass spec)
What drug can cause a false positive EIA for opiates?
ciprofloxacin
What drugs are most likely to be effective in the setting of nociceptive or inflammatory pain?
NSAIDs
What drugs are most likely to be effective in the setting of neuropathic pain or pain from central sensitization?
antidepressants and anticonvulsants
How do Gabapentin and Pregabalin work?
