Drugs Flashcards
What kind of drug is a phenothiazine? What kind of phenothiazine do we use?
Pre-anesthetic medication
Acepromazine
What are the actions of phenothiazines?
- anti-adrenergic (a1 blocker), antidopaminergic, anticholinergic (muscarine blocker), antihistaminic (H1 blocker), antiserotonergic (5-HT blocker), local anesthetic effects (ion channel blockade), anti-arrhythmic, NO ANALGESIA, anti-thrombotic actions
What are the effects of phenothiazines?
- sedation, hypotension, hypothermia, anti-emetic, anti-arrhythmic
What is the pharmacology of phenothiazines?
- contain 2 benzene rings that are linked by a sulphur & nitrogen atom
- highly protein bound (>90%)
- lipophilic - cross the BBB & placenta
- hepatic metabolism
What are the phenothiazines’ wide variety of actions?
primarily depress parts of the CNS which assist in the control of homeostasis:
- vasomotor control, thermoregulation, hormonal balance, acid-base balance, emesis
What are the mechanisms of action of phenothiazines?
- mental calming effect - mediated by ANTIDOPAMINERGIC actions in the CNS
- useful to calm, seem to reduce anxiety, anesthetic sparing
- overdose of these drugs will cause catalepsy
What are the negative side effects of phenothiazines?
- CARDIOVASCULAR effects: HYPOTENSION through vascular smooth muscle A1 receptor blockade
- RESPIRATORY effects: reduces the sensitivity of the respiratory center to CO2
- THERMOREGULATORY effects: hypothermia can occur due to disruption of thermoregulation & cutaneous vasodilation
What are the positive side effects of phenothiazines?
- ANTI-EMETIC: effect in central chemoreceptor trigger zone
- ANTI-ARRHYTHMIC: increases the concentration of epinephrine required to induce cardiac arrhythmias
- ANTI-HISTAMINE: contraindicated prior to allergy testing/skin biopsies
What is acepromazine?
- commonly used in vet med - calming effect
- 30-40% anesthetic sparing effect
- mild sedation when used alone, NO ANALGESIA
- commonly combined w/ A2-agonists, opioids
- used in cats, dogs, HORSES (do not use in breeding stallions - have been rare cases of penile prolapse), rarely used in Ru or exotics
- can be used in seizure prone animals
- can also be used for controlling emergence delirium during recovery from anesthesia
- solution is yellow in colour
- slow time to onset of effect, even after IV administration
- dose-dependent (duration & severity of side effects - HYPOTENSION)
What kind of drugs are benzodiazepines?
pre-anesthetic medication
What are benzodiazepines?
- ANTICONVULSANT
- AVOID using ALONE IV in Ca, Fe, Eq (EXCITEMENT possible in young, healthy animals; may become AGGRESSIVE)
- better combined w/ mu-opioids (IV or IM - combination good in SICK, OBTUNDED dogs)
- sedation when used for exotic animals
- reduces amount of major anesthetic (anesthetic sparing)
- muscle relaxation
- retrograde amnesia
- NO ANALGESIA
What is the pharmacology of benzodiazepines?
- consist of benzene rings fused to a diazepine ring
- well absorbed across mucous membranes
- significant first-pass metabolism if administered orally - need to increase dose
- highly protein bound (>95%)
- hepatic metabolism - oxidation & conjugation
What are the mechanisms of action of Benzodiazepines?
- act on specific benzodiazepine binding sites - which are associated w/ GABA(A) receptors
- depresses activity in reticular activating system, by enhancing GABA actions -> ANXIOLYSIS & SEDATION (dose dependent) - SEDATION IS UNRELIABLE IN SOME ANIMALS - CAN CAUSE EXCITMENT
- central GABA - enhancing activity -> ANTI-CONVULSANT effect
- act in the spinal cord - depress internuncial transmission -> MUSCLE RELAXATION
What are the side effects of benzodiazepines?
- minimal CARDIOVASCULAR effects
- minimal RESPIRATORY effects
- CNS depression: overdose can cause coma
What drugs are benzodiazepines?
- diazepam
- midazolam
What is important about diazepam?
- adheres to plastic syringes (takes up to 12 hrs)
- sensitive to light degradation
- propylene glycol carrier (pH 6.8): painful on IM injection & unreliable absorption
- active metabolites - Nordiazepam
- crosses placenta, reaches fetus, & remains in fetus: DO NOT use for c-sections unless antagonist (flumazenil) is available
What is important about midazolam?
- contains an imidazole ring: in acidic solution (pH < 4), ring opens & cmpd is water soluble; pH > 4, ring closes & cmpd becomes highly LIPOPHILIC
- can be administered IM, intranasal, transmucosal
- 2-3x more potent than diazepam
- inactive metabolites
- popular in EXOTIC ANESTHESIA (reliable sedation)
What is important about flumazenil?
Benzodiazepine ANTAGONIST at benzodiazepine binding site on GABA(A) receptor
- no side effects
- increases muscle tone to normal - improves ventilation
- useful for exotic animal anesthesia
- 30-60 mins duration IV, IM
What drugs are behaviour modifiers?
- Trazadone
- Gabapentin
What is important about trazadone?
- serotonin receptor antagonist & reuptake inhibitor
- some A1 receptor blocking action - possible hypotension
- oral administration, may be given before visit
- similar to using acepromazine to decrease stress
- can be combined w/ opioid
What is important about gabapentin?
- mechanism underlying its anxiolytic properties is unclear
- has an inhibitory effect on voltage gated calcium channels in neural tissue decreasing the release of glutamate w/in the CNS
- routinely used for treatment of chronic pain & epilepsy
- oral administration may be given before visit
What are the different injectable anesthetics?
- propofol
- alfaxalone
- ketamine
What is important about propofol?
- acts on GABA(A) receptors in CNS to produce anesthesia
- induction smooth & rapid: onset 40-90 secs & 1 dose last 5-10 mins
- short duration of action depends on REDISTRIBUTION: EXTRA-HEPATIC sites of metabolism - kidneys, lungs, GI tract
- recovery fast & smooth
- used for induction & maintenance (TIVA)
- no analgesia
- occasionally pain upon IV injection
- no tissue damage if injected perivascular
- vehicle is a lipid emulsion (‘Intralipid)
- PropoClear - lipid free formulation
- Propoflo 28 - contains preservative & is labelled for use up to 28 days after opening
What effects does propofol have on the cardiovascular system?
- cardiovascular depression is DOSE DEPENDENT
- myocardial depression
- venodilation - decreased BP
- resets baroreceptor reflex - increase in HR w/ drop in BP does NOT occur
- AVOID IN hypovolemic animals & patients w/ cardiac disease
What effects does propofol have on the respiratory system?
- respiratory depression is DOSE DEPENDENT
- post-induction apnea
- post-induction cyanosis
- supplement oxygen & pre-oxygenate
- mild bronchodilation
What effects can you occasionally get on induction &/or recovery with propofol?
- dogs: limb stiffness, paddling movements, opisthotonos, twitching
what is propofol recommended for?
- C-SECTIONS
- CEREBROPROTECTION: reduces CBF & cerebral metabolic rate
- patients w/ compromised LIVER function
What is important about propofol in Fe?
- reduced capacity for glucuronide conjugation
- propofol infusion (recovery from anesthesia delayed)
- repeated administration over several days: hemolysis & Heinz Body formation; clinical relevance has been questioned
What is important about alfaxalone?
- acts on GABA(A) receptors to CNS to produce anesthesia
- induction smooth & rapid: onset 15-45 secs & 1 dose lasts 5-10 mins
- short duration of action depends on REDISTRIBUTION
- recovery fast, quality improves w/ premedication
- used for induction & maintenance (TIVA) - rapidly metabolized
- no analgesia
- no pain upon injection
- no tissue damage if injected perivascular
- similar effects to Propofol
- can be administered IM
How does alfaxalone effect the cardiovascular system?
- cardiovascular depression is DOSE DEPENDENT
- hypotension (combination of myocardial depression & some peripheral vasodilation)
- compensation via reflex tachycardia (Baroreceptor reflex)
How does alfaxalone effect the respiratory system?
- respiratory depression is DOSE DEPENDENT
- post-induction apnea
What is alfaxalone good for?
- good muscle relaxation
- produces reliable sedation when given IM in cats
- excellent in reptiles (IM)
How does co-induction of another drug with alfaxalone or propofol work?
- combine alfaxalone OR propofol w/ another agent to minimize the amount required
- typical agents used include (Benzodiazepines (Midazolam or Diazepam); ketamine)
what is ketamine?
- DISSOCIATIVE ANESTHETIC AGENT - interrupts information reaching higher centers in the brain
- different from GABA(A) agonist drugs: cataleptoid state w/ slow nystagmus; muscle rigidity w/ higher doses; maintains cranial nerve reflexes - gag, swallow, palpebral, & central eye in dogs & cats (no ventral-medial rotation)
- racemic mixture (S(+)isomer is 2-4x more potent
What is important about ketamine?
- popular in vet med (high margin of safety)
- slow onset (30-90 sec) & longer duration (20-30 mins)
- USED FOR INDUCTION & MAINTAENANCE & ANALGESIA - will accumulate
- can be administered: IM, IV, SC, TM
- profound ANALGESIA (somatic > visceral; wind up pain (NMDA antagonist))
- sub-anesthetic doses can be used for reliable SEDATION
- neither anti- nor pro-convulsant
What are the mechanisms of action of ketamine?
- NMDA receptor antagonist - analgesic effects
- CNS voltage dependent Na+, K+, Ca2+ channels
- depression of CNS Acetyl Choline receptors
- some action at GABA(A) receptors
- depression of nociceptive cells in the dorsal horn of the spinal cord
Side effects of ketamine?
- muscle rigidity (catatonia): ALWAYS combine w/ muscle relaxant (benzodiazepine or a2-agonist)
- AVOID in CATS w/ compromised renal function
- auditory & visual stimuli disturbed during recovery can cause ‘emergence delirium’
- USE W/ OTHER DRUGS TO REDUCE SIDE-EFFECTS (benzodiazepines, A2-agonists, acepromazine)
How does ketamine affect the cardiovascular system?
healthy animals: indirect mild cardiovascular stimulation
- sympathomimetic effects last for 2-15 mins
- increase in cardiac work & myocardial oxygen consumption
- AVOID IN CATS w/ hypertrophic cardiomyopathy
Critically ill patients OR catecholamine depleted:
- may see mild direct myocardial depressant effects
How does ketamine affect the respiratory system?
- minimal respiratory depression
- bronchodilation
- laryngeal & pharyngeal reflexes are preserved
- irregular/periodic breathing pattern - apneustic breathing
Does ketamine cause behavioural side effects?
- can cause rough recoveries (head shaking, vocalization, dysphoria, salivation)
Why do we combine ketamine with other drugs?
- decrease the amount of ketamine needed
- eliminate unwanted side effects (improve recovery quality)
- produce good skeletal muscle relaxation
- improve visceral analgesia
- prolong the period of anesthesia/ immobilization
What is important about Ket-Val?
Ketamine/Diazepam
- IV induction agent in: Dogs, cats, neonatal foals, horses, calves, & cattle
- slow onset (30-90 sec)
- short acting, rapid recovery
- MINIMAL CARDIOVASCULAR SIDE EFFECTS
- MINIMAL RESPIRATORY SIDE EFFECTS
- DO NOT USE FOR C-SECTIONS (diazepam accumulates in neonates)
- less side effects than A2/ketamine
What are our options for combining an A2-agonist w/ ketamine?
- xylazine + ketamine
- dexmedetomidine + ketamine + opioid
What is important about xylazine + ketamine?
- good combination in large animals (horse, cattle) (IV)
- reliable for wildlife immobilization (IM)
- analgesia, muscle relaxation, & narcosis
- potent cardiopulmonary depression
- not recommended for routine use in cats & dogs
What is important about Dexmedetomidine + ketamine + opioid?
- “kitty-magic”
- wildlife, game ranch animals
- supportive care (provide oxygen)
- monitor closely
- A2 reversible (Atipamezole)
What are our A2 Agonists?
- are NOT pure A2 agonists
- newer A2 agonists have more specific action on the A2, & less action on the A1 receptors
- xylazine (Anased, Rompun)
- clonidine
- detomidine (Dormosedan)
- romifidine (Sedivet)
- medetomidine (Domitor)
- dexmedetomidine (Dexdomitor)
What are our A2 Antagonists?
- Atipamezole
- Yohimbine
-Tolazoline
What is important about Atipamezole?
- most selective A2 antagonist available
- competitive antagonist
- occasionally accompanied by: muscle tremors, tachycardia, over-alertness, transient hypotension, panting, defecation vomiting
- reversal of both sedation & ANALGESIA
- only labelled for IM administration
What is important about Yohimbine?
more of a historical drug
- general CNS stimulant w/ antagonist action at the A2 receptors
- tachycardia is possible
- used for xylazine (Eq, Ca, Fe)
- not in cattle (volume is too large)
What is important about Tolazoline?
more of a historical drug
- true A2 receptor antagonist
- more suitable volume in cattle
- can cause excitement when administered IV
What is the A2 agonist of choice for SMALL ANIMAL premed?
Dexmedetomidine
What is important about Dexmedetomidine?
- Highly selective for the A2 receptor
- IM in dogs & cats
- excellent sedative for healthy exotics
- always combine w/ an opioid for more reliable results
- if IV administration, decrease dose by half
- quality of sedation is profound but can override
- dose dependent CV & respiratory depression (choose your dose based on a number of factors: patient temperament, hydration status, anticipated pain level of the procedure)
- onset of action: 15 mins
- duration of action: 45 mins - 1 hr
- reversal available - Atipamezole
What is the A2 agonist used in Eq, Ru, & camelid premed?
xylazine
What is important about Xylazine?
- Eq & Ru IV, camelid IM
- excellent sedative in healthy patients
- quality of sedation is excellent
- reflex bradycardia is profound but transient
- onset of action: minutes
- duration of action: 30-45 mins
- can be reversed if necessary (RARE)
What is the A2 agonist used mainly in Eq for premed?
Detomidine
What is important about Detomidine?
- IV or IM in Eq
- good quality sedation (may be slightly more ataxic/depressed than w/ xylazine)
- onset & duration of action similar to xylazine
What do we use for sedation for minor procedures in small animals?
dexmedetomidine
- provides profound sedation for minor procedures: quill removal, laceration repair
- combine w/ an opioid to improve quality of sedation
- combine w/ local block if possible
- IV to effect
- sedation even more profound if administered IV - place a catheter so “top ups” are more easily administered
- reversible - get rid of drugs once procedure is complete
What do we use for sedation for standing procedures in large animals?
- xylazine
- detomidine
Xylazine for standing procedures?
xylazine
Eq
- teeth floats, minor lacerations
- feet firmly planted but can still kick so be aware
- often combined w/ butorphanol
- IV
Bo
- foot trims
- IM
- combine w/ butorphanol IM
- will result in recumbency in 15 mins
- duration of action ~60mins
- reverse w/ Tolazoline (IM to avoid excitement)
Detomidine for standing procedures?
- often combined w/ an opioid (butorphanol) for standing procedures
- for longer standing procedures, make up an infusion & administer to effect
What works well as an infusion during surgery?
Dexmedetomidine
- anesthetic sparing & analgesia
- Ca: LD + VRI IV
- Eq: IV (no loading dose necessary)
- be aware of bradycardia w/ bolus
- more effective when combined w/ an opioid infusion (fentanyl/remifentanil)
- not commonly administered to cats as an infusion
What should you use an an infusion in the post-operative period?
Dexmedetomidine
- benefits: analgesia & sedation
- indications: anxious dogs that need to be kept calm; fractious dogs that need to be in the ICU for post-operative care & handling; painful dogs that require something more than an opioid
- IV
Why would you add dexmedetomidine to a local anesthetic?
- prolongs duration of block
- mix w/ local anesthetic & administer in the same syringe
- some systemic uptake so may see increased levels of sedation
- amt is v sm
- need to dilute concentration of dexmedetomidine
- mech of action: vasoconstriction associated w/ the A2 agonist delays clearance of local anesthetic from the site
Dexmedetomidine in epidurals for small animals?
- not routinely used
- direct neurotoxic effects have not been fully tested
Dexmedetomidine in epidurals for large animals?
- prolongs duration of blockade
- easily accessible for practitioners
- does not produce motor blockade
- often combined w/ other drugs: local anesthetics (lidocaine); opioids
- produce analgesia (action on receptors in the substantia gelatinosa of the dorsal horn of the spinal cord)
- adverse effects (ataxia, recumbency): can be reversed
- systemic absorption occurs (CAUTION)
What drugs do we use in epidurals for Eq?
- xylazine
- detomidine
- romifidine
xylazine in horse epidural?
- provide 2.5 hrs of perineal analgesia
- no HL ataxia
- 1/5th the dose typically given systemically for sedation of Eq
- dilute in saline or lidocaine for injection
if combining w/ lidocaine, do not exceed 10 mL
- higher vol you put in, the further up you are going to block (dont want them going down)
detomidine in horse epidural?
- potent analgesic & sedative effects
- sedation, ataxia, recumbency, & CV effects can occur
- use low doses
- dilute in saline
- analgesia will spread cranially (T14)
- duration of analgesia shorter than xylazine (2 hrs)
- diuresis occurs (contraindicated in Eq w/ urinary obstruction)
romifidine in horse epidural?
- diluted in saline
- analgesia inconsistent (if it works, can provide up to 4 hrs of analgesia)
- spreads cranially, similar to detomidine
- sedation, bradycardia, & decreased RR has been reported
What drugs do we use in epidurals for cattle?
- xylazine alone
- xylazine combined w/ lidocaine
- romifidine
xylazine epidural for cattle?
- diluted in saline
- onset of action: 10 mins
- duration of action: 3-4 hr
xylazine + lidocaine epidural for cattle?
- onset of action: 5 mins
- duration of action: 6 hr
Side effects of xylazine epidurals in cattle?
- mild to moderate sedation
- mild ataxia
- decreased ruminal motility
- bradycardia
romifidine epidural for cattle?
- diluted in sterile saline
- analgesia & sedative effect was dose dependent in intensity & duration of action
What are the opioid antagonists?
- naloxone
- naltrexone
What is important about naloxone?
- pure mu, delta, kappa opioid antagonist
- can reverse all opioid agonist effects (respiratory depression, sedation, dysphoria) producing increased: alertness, responsiveness, coordination, perception of pain
- duration of action: 30-60 mins
- watch for renarcotization
What is important about naltrexone?
- clinical effects last approximately 2x as long as those of naloxone
- vet med: reversal of potent opioids for wildlife immobilization
What should you use to reverse a mu-opioid induced respiratory depression?
Butorphanol
- mu-antagonist
- kappa-agonist
- maintains analgesia (kappa)
- mu-opioid agonist: respiratory depression & sedation
What are the opioid agonists & their relative potencies?
potency is compared to morphine on an “equal-analgesic basis”
- morphine (1)
- meperidine (1/5)
- fentanyl (100)
- carfentanil (10000)
- buprenorphine (80)
- butorphanol (3-5)
Efficacy and Duration of the different opioids?
- mild & short: meperidine
- profound & long: morphine, hydromorphone, methadone
- odd ones: buprenorphine (moderate effect & long duration), fentanyl, sufentanil (profound effect & short duration)
Which opioid is given OTM (buccal)?
Buprenorphine
What is important about buprenorphine?
- Fe: acceptable bioavailability & analgesia
- Ca: high dose required (cost prohibitive, risk of swallowing)
- in clinical setting, IV or IM route provide better analgesia
- suitable for late postoperative analgesia
Which opioids do we administer transdermally?
- fentanyl patch
- transdermal fentanyl solution (Recuvyra)
what is important about a fentanyl patch?
- human safety considerations (should potentially not send home with O)
- patch technology evolved to reduce potential for abuse (was a reservoir (filled w/ liquid), now drug in an adhesive matrix (active drug mixed w/ polymer)
- spp differences in how skin affects drug movement
- lower bioavailability in Fe
- delayed onset (peak plasma concentration) - Ca: 12-24 hr (duration 3 days); Fe: 8-18 hr (duration up to 5 days)
Why do you need to continue pain assessment & monitoring during transdermal opioid administration?
- great individual variability in drug absorption
- changes in BODY TEMP, SKIN PREP, & PATCH PLACEMENT may affect rate of absorption, plasma fentanyl levels, & analgesic efficacy substantially
- care w/ heating pads (increased circulation increases uptake)
What is important about transdermal fentanyl solution (Recuvyra)?
- licensed for the control of postoperative pain associated w/ major orthopedic & soft tissue surgery in healthy dogs
- only in USA
- liquid solution applied to skin dorsally btwn shoulder blades (depot of fentanyl w/in lipid layer of the stratum corneum)
- no needle necessary
- requires risk training
- applied 2-4 hrs prior to surgery
- lasts for up to 4 days in dogs
- no peak effect
- adverse effects are long lasting (require repeated doses of naloxone)
How are opioids administered spinally/epidurally?
- often used in epidural or subarachnoid space to manage acute or chronic pain
- all opioids are lipid soluble but solubility differs btwn opioids
opioids w/ lower lipid solubility
- less systemic absorption
- slower onset time (passage across dura mater)
- longer duration & further cranial migration: morphine 12-24 hrs, hydromorphone 8 hrs, fentanyl: short duration & segmental analgesia
How are opioids administered intraarticularly?
- significant increase in mu-opioid receptors in articular & peri-articular tissues occurs after joint inflammation
- intra-articular administration of morphine after arthroscopy surgery (knee, elbow) as part of multimodal analgesia plan
Who are the full mu-agonists?
- superior analgesics
- treatment of moderate to severe pain
- morphine
- hydromorphone
- methadone
- fentanyl
- meperidine
- sufentanil, alfentanil, remifentanil
what is important about morphine?
- full mu opioid agonist
- ‘gold standard’ opioid to which others are compared, analgesia ++ to +++
- histamine release if administered IV (hypotension)
- vomiting
- can also be administered neuraxially & intra-articularly
What is morphine-6-glucaronide?
- active metabolite (650x as potent as morphine)
- pharmacological activities indistinguishable from morphine
- contributes significantly to clinical analgesia w/ chronic morphine administration
What is morphine-3-glucaronide?
- little affinity for opioid receptors
- may contribute to the EXCITATORY effects of morphine
What is important about hydromorphone?
- full mu opioid agonist
- 5-10x more potent than morphine
- analgesia: ++ to +++
- dose-dependent sedation, respiratory depression, bradycardia
- vomiting (45%)
- panting (dogs)
- hydromorphone-3-glucaronide can produce neuro-excitatory behaviours
- adequate analgesia for invasive surgery
What is important about methadone?
- full mu agonist
- NMDA antagonist
- NE & serotonin uptake inhibitor
- analgesia ++ to +++
- clinically similar to morphine
- no vomiting but panting
- no active metabolites
what is important about fentanyl?
- 75-125% more potent than morphine, analgesia +++
- intra & peri-operative pain
- fast onset, short half-life (suitable for repeated boluses or INFUSIONS)
- dose dependent respiratory depressant
- dose dependent bradycardia (may require treatment w/ anticholinergics)
- anesthetic sparing: isoflurane requirements are reduced by 53% (dogs)
- highly lipophilic (v large volume of distribution & long elimination half life
- too many repeated doses or too prolonged an infusion, may result in accumulation
- prolong context-sensitive half-lives (long recovery time, more problem in humans that dogs & cats)
What is important about Meperidine (Pethidine)?
- synthetic mu & kappa agonist
- 1/10th of the potency of morphine
- short duration, mild anesthesia
- histamine release
- decreased incidence of GER compared to morphine
- unique cardiovascular side effects vs other opioids
- significant negative INOTROPIC effects when administered alone to conscious dogs
- has modest ATROPINE-like effects (increase HR rather than typical bradycardia)
what is important about remifentanil?
- mu opioid agonist
- similar potency to fentanyl
- analgesia +++
- ultra-short-acting: context-sensitive half-time: 4 min (post 4hr CRI humans)
- only suitable for intraoperative use, need to administer other analgesics before infusion is terminated (to continue analgesia)
- metabolized by blood & tissue non-specific cholinesterases
- independent of hepatic function (useful for patients w/ hepatic disease)
What is important about tramadol?
- atypical mu receptor agonist
- inhibits uptake of serotonin & norepinephrine
- primary analgesic effect in humans is due to O-desmethyltramadol (M1 - 1st metabolite)
- M1 acts as a full mu opioid agonist
- analgesia (+)
- Ca: do not produce substantial amounts of M1; analgesic effects are predicted to be weak at best
- Fe: produce substantial amounts of M1 (likely an effective analgesic); bitter taste of oral preparation makes dosing a challenge
what is important about buprenorphine?
- partial mu agonist (weak kappa antagonist)
- 1000x higher affinity for mu receptor than morphine
- difficult to antagonize its effects
- moderate intrinsic activity
- analgesia ++
- slower onset time than other opioids (15-30 mins)
- long duration: 6-8 hrs
What is important about butorphanol?
- kappa agonist, mu antagonist
- originally labelled as an ANTITUSSIVE agent in Ca
- minimal effects on cardiopulmonary function
- no histamine release
- short-acting (30-90 mins)
- analgesia (+)
