Analgesics Flashcards
CV effects of opiates
cNS mediated decrease in HR
Decreased contractility with meperidine
Decreased BP due to decreased sympathetic outflow, vasodilation from histamine
Respiratory effects of opiates
Decreased RR, increased resting pCO2 ( supplemental O2 may mask hypo ventilation)
Decreased response to hypercarbia
Decreased response to hypoxia
Decreased airway reflexes
Neuro effects of opiates
Modest decrease in CMRO2
Decreased CBF
Decreased ICP
Increased seizure
GI effects of opiates
Decreased motility (emptying and peristalsis)-> ileus
Increased N/V -> stimulates chemoreceptors trigger zone
Increased common bile duct pressure
Urinary effects of opiates
Increased urinary retention
- especially with intrathecal use
Fentanyl
Intubation: 1-3 mcg/kg Intrathecal: 10-25 mcg/kg Epidural: 5-10 mcg/mL Analgesia: 0.5 mcg/kg load, 0.01-0.04 mcg/kg/hr maintenance Cleared by cyp450 Lipid soluble: rapid redistribution
Remifentanil
Induction: 1-3 mcg/kg Sedation: 0.5-1 mcg/kg load Increased resp depression with propofol Metabolized by esterases Rapid recovery regardless of infusion duration
Sufentanil
Sedation: 0.1-0.5 mcg/kg
Epidural: 10-15 mcg/10mL
Produces hypnosis at large doses, calculate from ideal body mass
Alfentanil
Intubation: 20-50 mcg/kg
Induction: 130-245 mcg/kg
mAC: 3-5 mcg/kg load, 0.25-1 mcg/kg/min
Rapid peak effect useful for single stimulus
- erythromycin and cimetidine inhibit clearance
Morphine
Analgesia: 2-10 mg Infusion: 0.8-10 mg/hr Renal clearance, some active metabolites Crosses BBB, peak st 10-40 min Histamine release
Dilaudid
Analgesia: 0.4-2 mg IV
Liver metabolism, active metabolites
Less histamine release and useful alternative to morphine
Meperidine (Demerol)
Indication: mod-severe pain
Sedation: 50-150 mg q3-4 hr
Liver metabolism
Direct myocardial depressant, metabolite linked to CNS excitation
Methadone
Indication: chronic pain and opioid withdrawal Dose: 2.5-10 mg PO Opiate agonist and NMDA antagonist Liver and renal excretion 13-100 hr half life
Oxycodone
Indications: mod-severe pain
Dose: 5-15 mg
Poor metabolizes may not achieve adequate effect
High abuse potential
Codeine
Mild-mod pain, cough suppression
Dose: 15-60 mg PO
Metabolized to morphine
Raises pain threshold, lower addictive potential
Mixed opiates
Agonist-antagonist effects decrease efficacy
- decreased dependence and they have a ceiling effect unlike pure opiates
Opioid General comments
Receptors: mu, kappa, delta -> inhibit ascending nociceptive and activate descending control
- dose dependent analgesia, amnesia at large doses
- pts report improved pain but still aware
- pruritus
Ketamine
NMDA receptor antagonist Uses: analgesia, anesthesia Dose: 0.15-0.5 mg/kg bolus Potent analgesic, decreased post-op opioids - lots of emerging uses
Tramadol (ultram)
Opioid agonist and spinal inhibition of pain
Dose: 25 mg increasing by 25 mg
Hepatic clearance
Less resp and GI effects, possible seizures
Possible serotonin syndrome with other drugs
Naloxone (narcan)
Opiates antagonist (competitive inhibition, used in overdose and reversal)
Dose: 0.2-4 mg IV with max of 10 mg
Onset: 1-2 min, lasts 4 hrs may need to revise
Precipitates opiate withdrawal
Hepatic metabolism and renal elimination
Methylnaltrexone (relistor)
Opiate antagonist (tx for opiate induced constipation) Dose: 0.15 mg/kg (
Fentanyl transdermal
Sustained release opiate therapy (chronic pain)
12.5-100 mcg/hr patches (peak at 12 hrs)
Lidocaine patch
Indications: neuropathic pain, inflammatory conditions
Dose: 1-3 patches with 12 hrs on and 12 hrs off
Blocks sodium channels
Minimal systemic absorption but local skin irritation
NSAIDS
Analgesic, anti inflammatory, antipyretic
Have ceiling effect unlike opiates (but can worsen side effects)
Inhibits COX -> decrease PGs (want cox 2 blocked)
SE: guy mucosa irritation, bronchi spasm, platelet aggregation, renal perfusion
Nonselective COX inhibitors
Used for pain and fever (Tylenol)
325-650 mg q6h PO (10 min)
1000 mg q6h IV (5 min)
Liver clearance (toxicity)
Not anti inflammatory, no GI irritation, platelet effects
Hepatic necrosis from NAPQI -> N-acetylcysyeine replaces glutathione
Propionic acid derivatives
Ibu: 200-800 mg q6h
Naproxen: 250 mg q6-8h
Ketorolac (toradol)
Dose: 30 mg IV q6h (max duration of 5 days)
Both hepatic and renal metabolism
Avoid in elderly and renal insufficiency
Aspirin
Analgesic/antipyretic/antiplatelet 325-650 mg q4-6 Irreversibly acetylates cox Stopped 5-10 days before surgery Contraindicated in bleeding, ulcers, hemophilia
Selective cox-2 inhibitor
Celebrex- used for osteoarthritis and RA
Dose: 200 mg daily
Potential less GI effects
Associated with CV events, HTN, fluid retention
