JUST DOSES AND OTHER NUMBERS Flashcards
pKa of fentanyl
8.4
onset of IV morphine
15-30 minutes (more nonionized than fentanyl but really not lipophilic)
ex: think about 9% of fentanyl being nonionized but 20% of morphine being nonionized
pKa of morphine
less than fentanyl (8.4)
7.9
active metabolite of morphine
(5-10% of metabolites) morphine-6-glucuronide
longer duration of action, 65x more potent than morphine
fentanyl onset
1-3 minutes
fentanyl potency compared to morphine
75-125x more potent
Vd of fentanyl
LARGE, >80% leaves the plasma in less than 5 minutes
(lowest ratio of nonionized to ionized, but highest lipophilicity)
3-4L
active metabolite of meperidine
90% demethylization to normeperidine (other one is hydrolysis to get meperidinic acid)
1/2 as active as meperidiine
T1/2 is 15 hrs! 30+ if renal failure pt!!
CS 1/2 time of fentanyl & sufentanil
increases with gtt >2 hrs
doses of fentanyl
- to block SNS response to surgical stimulation, and induction/intubation: 1-3 ug/kg prior to induction
- as sole surgical anesthetic (pure fentanyl induction - rare): 50-150 ug/kg
(transdermal patch applied preop and left for 24 hrs –> decreases IV requirements)
sufentanil dose
analgesia: think 5-10x more potent than fentanyl (so go with 1/10 dose)
0. 1-0.4 ug/kg
induction dose can cause chest wall rigidity (vs laryngeal?)
alfentanil pKa
6.5
alfentanil dose
- 15 μg/kg IV – blunts stim of laryngoscopy
- 30 μg/kg IV – catech response to noxious stim
- 150-300 μg/kg IV – produces unconsciousness (induction)
- Combo with inhaled anesthetic 15-150 ug/kg/hr
Vd of remifentanil versus fentanyl
fentanyl: 3-4 L/kg (large distribution)
remifentanil: 0.5 L/kg
remifentanil CS 1/2 time
4 minutes
plasma esterases in the bloodstream are always working
remifentanil dose
Remi is a tiny mouse, remi gets a tiny dose.
induction: 1 mcg/kg bolus, followed by gtt of 0.05-0.2 mcg/kg/min
analgesia: gtt same as induction gtt dose
sedation: 0.05-0.1 mcg/kg/min in combo with midaz 2 mg
drugs so far that have sz-like activity
etomidate, fentanyl, remifentanil, hydromorphone
tramadol may lower sz threshold
T1/2 methadone
12 hrs
hydromorphone dose
5x more potent than morphine, so ~2 mg?
slightly shorter duration of action
methadone dose
Think quarter and 20
for opioid w/d:
- Can substitute for morphine at ¼ the dosage
- 20 mg IV, produces postop analgesia >24 hours
- But not as much euphoria
chronic pain medication use effect on opioid dosing
you might have to give HIGHER than the normal dosing range to get effect
nalbuphine use and dose, T1/2
true agonist-antagonist: chemically related to oxymorphone and naloxone
analgesic properties of morphine, 1/4 antagonist of nalorphone
T1/2 3-6 hours
aside: if given before opioid, it can reduce effects of morphine-like drugs intraop. If given after opioid, it can reverse depression of ventilation effects (up to 30 mg) but maintain analgesia
dose of naloxone
1-4 mcg/kg IV
5 mcg/kg/hr can fix depression of ventilation without affecting analgesia
“I would not give the whole dose at once”
PO 1/5 as effective bc of 1st pass in liver
T1/2 of naloxone
30-45 minutes
“effects of the reversal agent don’t last as long as the narcotic”
nalmefene dose
Nalme-fene, 15!
15-25 mcg IV until the effect is achieved
Max dose 1 mcg/kg
neuraxial (intrathecal) dose of fentanyl
10-15 mcg TOTAL
goes through the dura, into the CSF
dose of toradol
(non-selective NSAID)
15 mg IV or IM q6hr
decrease dosing (or just avoid it honestly) for renal pts
celebrex (celecoxib) dose
(COX-2 inhibitor)
400 mg PO preop
200 mg BID x 5 days postop
Vd of NSAIDs
LOW, 0.1-0.3 L/kg
T1/2 of ketorolac
6 hrs
dose of APAP
325-650 mg q4-6hr
Total: 4g/24hr
2g/24 hr for ETOH pts
IV prep 1g/6hrs
Ofirmev. Same total dose - 4g/24hr.
gabapentin dosing (part of ERAS protocol)
1200 mg 1-2 hrs preop
600 mg q8hr x 14 days
pKa of lidocaine
“just above physiologic pH”
weak base, not very lipophilic
lidocaine dose (ERAS)
induction: 1.5 mg/kg IV bolus
(IBW bc this is not very lipophilic)
1-2 mg/kg/hr gtt
Magnesium Sulfate dose (ERAS)
30-50 mg/kg bolus
10 mg/kg gtt
(2g is a normal bolus dose, don’t give it all at once, or do a 15-min bolus. 1g/hr is a normal gtt rate)
ketamine dose (ERAS), ketamine dose for induction, ketamine dose for analgesia
ERAS: 0.5-1 mg/kg (but usually just do 0.5mg/kg), followed by gtt
INDUCTION: 1-2.5 mg/kg IV, takes 2-3 minutes to start working, IM 4-8 mg/kg, PO 10mg/kg
ANALGESIA: 0.2-0.5 mg/kg
analgesia < ERAS < induction dosing
dexmedetomidine dosing (ERAS)
“0.5-2 mcg/kg”
really will give 4 mcg at a time
drugs so far that are acids
propofol, barbiturates, NSAIDs
dose of succinylcholine, time til paralyzed
1.0 mg/kg
(low Vd - based on IBW)
creates intubating conditions in ~60 seconds, laryx ~34 seconds, recovery of 90% muscle strength in 9-13 minutes
T1/2 succinylcholine (from Stoelting)
47 seconds
intubating dose of atricurium
0.5 mg/kg
intubating dose of cisatricurium
0.1 mg/kg
intubating dose of mivacurium
0.15 mg/kg
intubating dose of pancuronium
0.08 mg/kg
onset time to maximal block - 2.9 minutes
intubating dose of vecuronium
0.1 mg/kg
onset time to maximal block - 2.4 minutes
intubating dose of rocuronium
0.6 mg/kg
onset time to maximal block - 1.7 minutes
max effective dose of neostigmine
0.04-0.08 mg/kg (40-80 mcg/kg)
max dose 6mg
70 kg pt, 2-4 mg for reversal
max effective dose of edrophonium
1.0-1.5 mg/kg
glycopyrrolate dose
0.005-0.01 mg/kg (5-10 mcg/kg)
atropine dose
0.007-0.01 mg/kg
sugammadex dosing
- TOF > 2 – 2 mg/kg
- TOF 1-2 – 4 mg/kg
- TOF 0 – 8-16 mg/kg
plasma [ ] curve
PK! Think ADME -Y axis [vertical] = concentration -X axis [horizontal] = time -Know it’s IV bc no 1st-pass effect -Distribution 1st part - alpha Drug that wears off bc of distribution: propofol, fentanyl, all the induction agents
- Elimination - beta
- Drug that is offset bc of this: morphine, diazepam (anything with an active metabolite)
dose-response curve
- Efficacy (y-axis) - effect
- Potency (x-axis) - dose
- Don’t know how potent the drug is, unless you have something to compare it to
- Test: lots of dose-response curves and you’ll be asked questions about those drugs
- Lipophilic drugs tend to wear off bc of redistribution. Nonlipophilic drugs tend to wear off bc of metabolism/elimination
- Morphine has a longer half-life than ____
What drugs have a low Vd?
remifentanil, NSAIDs, NMBDs
draw an ester linkage
C (=O)OC
phenylpiperidines
– just need to know that they’re phase I dealkylation processes
*No n versus o dealkyl….
therapeutic index
LD50/ED50 “The Whole Index of the Drug”
therapeutic window
TD50/ED50 “Window – where we live”
- ED95 in between the ED50 an TD50
- Captures top curve of the ED, bottom curve of TD
“Out of 100 pts, 95 will get pain relief, and only 5 will get constipation”
drug that can be given to treat opioid-induced biliary spasm
glucagon 2 mg will reverse smooth muscle spasm without antagonizing analgesic effects (biggest culprit is morphine), but you really should just avoid it if your pt is having a cholecystectomy
drug that you can give to combat GI SEs of opioids
narcan works everywhere, but methylnaltrexone works only in the gut
what 2 drugs act on DA receptors to produce antiemetic effects?
- butyrophenones, phenothiazines
- this supports the claim that opioid-induced N/V is due to activation of DA-2 receptors in the chemoreceptor trigger zone of the medulla (other receptor is 5HT3-serotonin)
T1/2 morphine
1.7-3.3 (stoelting)
