opioid pharmacology
TRANSCRIPT
Comparative Opioid Comparative Opioid PharmacologyPharmacology
DisclosureDisclosure
Analgesia is a labeled indication for all of the approved drugs I will be discussing.
I’ve consulted with Glaxo (remifentanil), Abbott (remifentanil), Janssen (Duragesic), Alza (Duragesic), Anesta (Actiq), and Delex (liposomal fentanyl)
Classical Opioid Classical Opioid PharmacologyPharmacology
Analgesiamodest to profound with no ceiling effect
Sedationmodest to profound, but has a ceiling effect
unconsciousness cannot be assured
Reduces MACwith a ceiling effect
Synergy with hypnoticsmodest at causing sedationprofound at suppressing movement response to noxious
stimulation
Classical Opioid Classical Opioid PharmacologyPharmacology
High dose opioids are associated with hemodynamic stability
High dose opioids attenuate the stress response
Classical Opioid Classical Opioid PharmacologyPharmacology
Urinary retention Ileus Addiction potential
Ventilatory depression Muscle Rigidity Nausea, Vomiting Pruritis
Pure Pure agonists agonists
IntraoperativeFentanylAlfentanilSufentanilRemifentanil
PostoperativeMorphineHydromorphoneMethadone
MorphineMorphineThe prototypical opioidThe prototypical opioid
MorphineMorphine
Endogenous Ligand Slow rise to peak effect
Absolute peak analgesic effect is at 90 minutes after bolus injection!
Active metabolite Morphine-6-glucuronide is unlikely to contribute to analgesic
effects at standard OR doses. Will contribute to effects with chronic dosing Especially in renal failure
Not as full efficacy as fentanyl series of opioids
Simulation of MorphineSimulation of MorphineTime CourseTime Course
Dahan et al. Anesthesiology. 2004 Nov;101(5):1201-9.
FentanylFentanylThe ever morphing moleculeThe ever morphing molecule
FentanylFentanyl
Among the pharmacologically cleanest opioid
The first of the “fentanyl” series (obviously…)
Available in transdermal, submucosal, sublingual, and (soon) inhaled forms.
How we think of fentanyl:How we think of fentanyl:(small part of the market)(small part of the market)
Fentanyl morph 1:Fentanyl morph 1:DuragesicDuragesic
Fentanyl morph 2: ActiqFentanyl morph 2: Actiq
Fentanyl morph 3:Fentanyl morph 3:E-trans fentanylE-trans fentanyl
Viscusi et al, JAMA 2004 291:1333
Fentanyl morph 4:Fentanyl morph 4:Inhaled liposomal fentanylInhaled liposomal fentanyl
Hung et al, Anesthesiology 1995 83:277-84
Fentanyl morph 5:Fentanyl morph 5:Inhaled fentanyl aerosolInhaled fentanyl aerosol
Mather et al, Br J Clin Pharmacol 1998 46:37
Fentanyl morph 6:Fentanyl morph 6:Effervescent Fentanyl Effervescent Fentanyl
(OraVescent)(OraVescent)
Pather et al, http://www.drugdeliverytech.com/cgi-bin/articles.cgi?
idArticle=5
SufentanilSufentanilNewly morphing moleculeNewly morphing molecule
SufentanilSufentanil
10 fold more potent than fentanyl Slightly slower onset More rapid recovery Very clean pharmacologically
Sufentanil morph 1:Sufentanil morph 1:Implantable sufentanil deliveryImplantable sufentanil delivery
http://www.drugdeliverytech.com/cgi-bin/articles.cgi?idArticle=115
MeperidineMeperidine
Bad Drug! Little role in the management of pain Toxic metabolite
Normeperidine seizures Renally excreted
Negative inotrope Causes tachycardia (anticholinergic) Complex interactions
MAO syndrome when combined with MAO inhibitors
Useful for shivering, perhaps as a local anesthetic
HydromorphoneHydromorphoneA better morphineA better morphine
HydromorphoneHydromorphone
A rapid onset morphine No histamine release About 8 fold more potent than morphine No active metabolite Good choice for PCA, post-op analgesia
AlfentanilAlfentanil
Less potent than fentanyl Much more rapid onset (including more
rapid onset of rigidity and respiratory depression)
Much more evenascent effect with a single bolus
With brief infusions will be almost indistinguishable from fentanyl, except for potency
RemifentanilRemifentanil
Similar potency to fentanyl Pharmacokinetics are in a class by
themselves (ester metabolism) Reduce the dose by about 2/3s in the elderly No pharmacokinetic interactions Onset is similar to alfentanil
MethadoneMethadoneThe Under-Utilized OpioidThe Under-Utilized Opioid
MethadoneMethadone
Longest terminal half-life (about 1 day) May accumulate during titration to steady
state Supplied as a racemic mixture
L methadone is an opioid antagonist D methadone is an NMDA antagonist
Fundamental PK/PD ParametersFundamental PK/PD Parameters
Fentanyl Alfentanil Sufentanil Remifentanil Morphine Methadone Meperidine HydromorphoneVolumes (l)
V1 12.7 2.2 17.8 4.9 17.8 7.7 18.1 11.5V2 50 7 47 9 87 12 61 115V3 295 15 476 5 199 184 166 968
Clearances (l/min)Cl1 0.62 0.20 1.16 2.44 1.26 0.13 0.76 1.33Cl2 4.82 1.43 4.84 1.75 2.27 2.19 5.44 3.45Cl3 2.27 0.25 1.29 0.06 0.33 0.38 1.79 0.92
Exponents (min-1)a 0.67 1.03 0.48 0.96 0.23 0.50 0.51 0.51b 0.037 0.052 0.030 0.103 0.010 0.025 0.031 0.012g 0.0015 0.0062 0.0012 0.0116 0.0013 0.0005 0.0026 0.0005
Half Lives (min)t 1/2 a 1.03 0.67 1.43 0.73 2.98 1.38 1.37 1.35t 1/2 b 19 13 23 7 68 28 22 59t 1/2 g 475 111 562 60 548 1377 271 1261
Blood Brain Equilibrationke0 (min-1) 0.147 0.770 0.112 0.525 0.005 0.110 0.067 0.015
t 1/2 ke0 (min) 4.7 0.9 6.2 1.3 139 6.3 10.3 46
Tpeak (min) 3.7 1.4 5.8 1.6 93.8 11.3 8.5 19.6VD Peak Effect (l) 76.9 6.0 94.9 17.0 590.2 30.9 143.3 383.3
Comparative Opioid PKComparative Opioid PK
Minutes since bolus injection
0 240 480 720 960 1200 1440
Per
cent
of
initi
al c
once
ntra
tion
0.01
0.1
1
10
100
Methadone
Remifentanil
FentanylSufentanil
Alfentanil
HydromorphoneMorphine
Meperidine
Comparative Opioid PKComparative Opioid PK
Minutes since bolus injection
0 5 10 15 20 25 30
Per
cent
of i
nitia
l con
cent
ratio
n
1
10
100
Methadone
Remifentanil
Fentanyl
SufentanilAlfentanil
Hydromorphone
Morphine
Meperidine
Comparative Onset of Comparative Onset of Opioid Drug EffectOpioid Drug Effect
Minutes since bolus injection
0 5 10 15 20
Per
cent
of
peak
eff
ect
site
con
cent
ratio
n
0
20
40
60
80
100Methadone
Remifentanil
Fentanyl
Sufentanil
Alfentanil
Hydromorphone
Morphine
Meperidine
Context Sensitive Half TimeContext Sensitive Half Time
Infusion Duration
0 120 240 360 480 600
Min
utes
to
50%
dec
rem
ent
in p
lasm
a co
ncen
trat
ion
0
60
120
180
240
300
Methadone
Remifentanil
Fenta
nyl
SufentanilAlfentanil
HydromorphoneMorphine
Meperidine
50% Effect Site Decrement Time50% Effect Site Decrement Time
Infusion Duration
0 120 240 360 480 600
Min
utes
to
50%
dec
rem
ent
in e
ffec
t si
te c
once
ntra
tion
0
60
120
180
240
300
Methadone
Remifentanil
Fentanyl
Sufentanil
Alfentanil
Hydromorphone
Morphine
Meperidine
20% Effect Site Decrement Time20% Effect Site Decrement Time
Infusion Duration
0 120 240 360 480 600
Min
utes
to
20%
dec
rem
ent
in e
ffec
t si
te c
once
ntra
tion
0
30
60
90
120
Methadone
Remifentanil
Fentanyl
Sufentanil
Alfentanil
Hydromorphone
Morphine
Meperidine
Rise to Steady StateRise to Steady State
Infusion Duration
0 120 240 360 480 600
Fra
ctio
n of
Ste
ady
Sta
te
0
20
40
60
80
100
Methadone
Remifentanil
FentanylSufentanil
Alfentanil
Hydromorphone
Morphine
Meperidine
Relative PotencyRelative Potency
Fentanyl Alfentanil Sufentanil Remifentanil Morphine Methadone Meperidine HydromorphoneMEAC (ng/ml) 0.6 14.9 0.056 1.0 8 60 250 6Equipotent bolus dose (g) (g) (g) (g) (mg) (mg) (mg) (mg)
at peak effect 50 92 5.5 17 4.9 1.9 37 2.5at 10 minutes 50 197 4.4 72 5.3 1.4 28 1.9at 30 minutes 50 174 3.9 282 2.0 0.9 17 0.9at 60 minutes 50 175 4.8 1,680 1.0 0.9 14 0.6
Equipotent infusion rate (g/hr) (g/hr) (g/hr) (g/hr) (mg/hr) (mg/hr) (mg/hr) (mg/hr)at 1 hour 100 323 9 135 5 2 43 2at 2 hours 100 332 10 182 3 2 38 2at 4 hours 100 365 12 252 2 3 36 2at 6 hours 100 409 13 310 2 3 37 2at 12 hours 100 536 15 436 2 3 40 2at 24 hours 100 675 16 554 2 3 45 2
50 50 g fentanyl at 10 minutesg fentanyl at 10 minutes
Alfentanil 197 gSufentanil 4.4 gRemifentanil 72 gMorphine 5.3 mgMethadone 1.4 mgMeperidine 28 mgHydromorphone 1.9 mg
50 50 g/hour fentanyl at 2 hoursg/hour fentanyl at 2 hours
Alfentanil 332 g/hrSufentanil 9.6 g/hrRemifentanil 182 g/hrMorphine 3.3 mg/hrMethadone 2.3 mg/hrMeperidine 38 mg/hrHydromorphone 1.8 mg/hr
Opioid ReceptorOpioid Receptor
Evidence of Evidence of opioid subtypes opioid subtypes
Only about 50% cross tolerance between morphine, methadone, fentanyl
Explains why rotating opioids in chronic pain is probably a good idea
CXBK mouse is insensitive to morphine, but has normal response to M6G and fentanyl
Selective response to opioid antagonistsMorphine-6-glucuronide, the outlier
Gavril Pasternak, Life Sciences 2001:68, 2213
NaloxonazineNaloxonazine
Selectively antagonizes morphine analgesia in animals1 is considered naloxonazine sensitive
Does not antagonize morphine-induced ventilatory depression or GI effects2 is considered naloxonazine insensitive
Gavril Pasternak, Life Sciences 2001:68, 2213
Morphine-6-glucuronideMorphine-6-glucuronide
Active metabolite of morphine, about 100 fold more potent intrathecally, but enters the CNS VERY slowly
Has analgesic activity in the CXBK mouse that is insensitive to morphine
Actions blocked by naloxonazine (hence, 1)Has a unique antagonist, 3-O-methylnaxtrexone
Also antagonizes heroin self administration, little affect on morphine
Subtype of 1
MOR-1 knockout (exon 1) has normal sensitivity to morphine-6-glucuronide
Gavril Pasternak, Life Sciences 2001:68, 2213
Gavril Pasternak, http://www.mskcc.org/mskcc/html/11384.cfm
MOR-1 gene splice variantsMOR-1 gene splice variants(gene=OPRM)(gene=OPRM)
Antisense lowers Antisense lowers morphinemorphine analgesia analgesia(no effect on m6g)(no effect on m6g)
Gavril Pasternak, Life Sciences 2001:68, 2213
Gavril Pasternak, Life Sciences 2001:68, 2213
Antisense lowers Antisense lowers m6gm6g analgesia analgesia(no effect on morphine)(no effect on morphine)
Morphine-6-glucuronideMorphine-6-glucuronide
Very slow transit across blood brain barrier.Not a substrate for p-glycoprotein, but appears to be a
substrate for probenecid inhibited transporters (Anesthesiology 2004:101 1394)
Recently a peptide based carrier demonstrated 4 fold increase in uptake and potency (JPET 2005:12 epub).
Some data show higher affinity for 1, and lower affinity for 2, compared to morphine.
Some suggestion that M6G is associated with less ventilatory depression for the amount of analgesia (e.g., Romberg et al, Anesthesiology 2004 100:120)
11 selective agonists? selective agonists?
Despite evidence now 25 years old of differential response to antagonists, nobody has found a 1 selective agonist
Biggest argument against it: Paul Janssen spent years looking for one, screening over 70,000 possible ligands
Reason for hope: perhaps our improved knowledge of MOR-1 splice variants will help identify the required pharmacophore
Don’t hold your breath…
““Power corrupts,Power corrupts,PowerPoint corrupts absolutely”PowerPoint corrupts absolutely”