Updated: 3/3/2021

Analgesics

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Analgesic Drug Introduction
  • Analgesic medications can be broken down into the following categories
    • antirheumatic agents
    • muscle relaxants
    • narcotic agonists
    • narcotic agonists-antagonists
    • narcotic antagonists
    • narcotic analgesic combo
    • NSAIDS
    • other analgesics
Analgesic Drug Table
 
Antirheumatic Agents
Name
Mechanism of Action
 Key Indication
 Key Toxicity
TNFα Inhibitors
Infliximab
  • Monoclonal antibody against TNF-alpha (infliximab, adalimumab, certolizumab)
  • Decoy receptor for TNF-alpha (etanercept)
  • Disease modifying drug for Crohn's, psoriasis, rheumatoid arthritis, ankylosing spondylitis 
  • Opportunistic infection, in particular mycobacterial infection due to TNF destabilization of granulomas
Adalimumab
Etanercept
Gold Preparations
Auranofin
  •  Gold complex
  • Not commonly used
  • Gold toxicity
  • Myelosuppression
Aurothioglucose
Other Antirheumatics
Cyclophosphamide
  • Alkylating agent - nitrogen mustard type
  • Hodgkin lymphoma
  • Leukemia
  • RA
  • Alkylating agent
  • Hemorrhagic cystitis (treat with mesna)
  • Myelosuppression
Azathioprine
  • Purine synthesis inhibitor
  • Renal transplant immunosuppresion
  • Autoimmune disease
  • PTLPD
  • Myelosuppression
Hydroxychloroquine
  • Lysosomal accumulation/inhibition
  • Malaria prophylaxi
  • SLE
  • RA
  • Can excacerbate G6PD deficiency 
Methotrexate
  • Dihydrofolate reductase competitive inhibitor
  • RA
  • Psoriasis
  • Anti-folate chemotherapy
  • Ectopic pregnancy
  • Must monitor pregnancy status, extremely toxic to fetus including neural tube defects 
Muscle Relaxants
Carbamic Acid Esters
Methocarbamol
  • Mechanism unknown
  • Potential carbonic anhydrase inhibition
  • Adjunct for tetanus, muscle spams
  • Ataxia
  • Seizures
Carisoprodol
  • Mechanism unknown
  • Central skeletal muscle relaxant
  • Muscle spams
  • Musculoskeletal pain
Other
Baclofen
  • GABAB receptor activation
  • Spasticity
  • CNS depression
  • Respiratory depression 
Cyclobenzaprine
  • Mechanism unkown
  • Muscle relaxant
  • Muscle spasms
  • Contraindicated with MAOIs
  • Heart block
Dantrolene
  • Binds ryanodine receptor
  • Decreases calcium release from the sarcomplasmic reticulum
  • Neuroleptic malignant syndrome
  • Malignant hyperthermia
  • Hepatotoxicity
  • CNS depression 
Metaxalone
  • Mechanism unkown
  • CNS depression
  • Musculoskeletal pain
  • CNS depression 
Orphenadrine
  • Ach receptor antagonism
  • H1 receptor blocker (antihistamine)
  • NMDA receptor antagonist
  • Norepinephrine reuptake inhibitor
  • Na+ channel blocker
  • K+ channel blocker
  • Discontinued in the U.S.
  • Anticholinergic effects 
Tizanidine
  • Central α2 agonist (Gi coupled)
  • Spasticity
  • Hypotension (α2 agonist)
Diazepam
  • GABA type A positive modulator
  • Anxiety
  • Status epilepticus
  • Alcohol withdrawal
  • Seizures
  • Sedative
  • Muscle relaxant
  • Dependency
  • Abuse potential 
Narcotic Agonists
Alfentanil
  • Opioid analgesic (short acting)
  • Induction agent for general anesthesia
  • Respiratory depression
  • Dependency
  • Abuse potential
Codeine
  • Opioid (μ agonist)

  • Acute pain
Levorphanol
Oxymorphone
Hydromorphone
Morphine
Oxycodone
Meperidine
  • Acute pain
  • Sedation
Dextropropoxyphene
  • Antitussive
  • Mild pain
  • Restless leg syndrome
Methadone
  • Very long acting opioid (μ agonist)
  • Opioid dependence
  • Chronic pain
Fentanyl
  • Very potent opioid (μ agonist)
  • Induction agent
  • Chronic pain
Narcotic Agonists-Antagonists
Buprenorphine
  • Partial opioid receptor (μ) modulator
  • Moderate pain
  • Opioid dependence
  • Respiratory depression
  • Seizures
  • Bradycardia
Butorphanol
  • Partial agonist/antagonist activity of μ receptors
  • Competitive antagonis of κ opioid receptors
  • Anesthesia induction
  • Seizures
  • CNS depression
  • Anticholinergic effects
Nalbuphine
Pentozocine
  • Agonist-antagonist at opioid (μ) receptor
  • Mild pain
  • Opioid dependence
  • Hypertension
  • Tachycardia
Buprenorphine/naloxone
  • Partial opioid receptor (μ) modulator (buprenorphine)
  • μ receptor antagonist (naloxone)
  • Opioid dependence maintenance therapy
  • Seizures
  • CNS depression
  • Anticholinergic effects
  • Opiod withdrawal if abused
Narcotic Antagonists
Naloxone
  • μ receptor antagonist
  • Acute opioid toxicity
  • Opioid withdrawal
Narcotic Analgesic Combo
Acetaminophen/oxycodone
  • μ agonist + unknown mechanism of acetaminophen
  • Acute pain moderate
  • Respiratory depression
  • Dependency
  • Abuse potential
Acetaminophen/hydrocodone
NSAIDS
Salicylates
Aspirin
  • Irreversible inhibitor of COX-1
  • Antiplatelet therapy for CAD
  • Pain
  • Antipyretic
  • Reye's Syndrome in children
  • Tinnitus
  • Mixed metabolic acidosis and respiratory alkalosis  
Proprionic Acids
Ibuprofen
  • COX inhibitor
  • Mild pain
  • Gastritis
  • NSAID nephropathy
  • GI bleeding
Naproxen
Acetic Acids
Ketorolac
  • COX inhibitor (competitive)
  • Mild pain
  • Gastritis
  • NSAID nephropathy
  • GI bleeding
Indomethicin
  • COX inhibitor
  • Patent ductus arteriosus
  • Pain
COX-2 Selective Inhibitors
Celecoxib
  • COX-2 inhibition
  • Osteoarthritis
  • Increased risk of MI, thrombosis in at-risk individuals
Other Analgesics
Acetominophen
  • Not well characterized
  • Antipyrretic
  • Mild pain
  • Hepatotoxicity 
Tramadol
  • Opioid agonist (μ)
  • Chronic, moderate-severe pain
  • Hepatotoxicity
  • Seizures
  • Withdrawal symptoms  
 

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Questions (1)

(M2.PH.14.35) A 58-year-old man presents to the emergency department with a chief complaint of ringing in his ears that started several hours previously that has progressed to confusion. The patient denies any history of medical problems except for bilateral knee arthritis. He was recently seen by an orthopedic surgeon to evaluate his bilateral knee arthritis but has opted to not undergo knee replacement and prefers medical management. His wife noted that prior to them going on a hike today, he seemed confused and not himself. They decided to stay home, and roughly 19 hours later, he was no longer making any sense. Physical exam is notable for a confused man. The patient's vitals are being performed and his labs are being drawn. Which of the following is most likely to be seen on blood gas analysis?

QID: 104309
1

pH: 7.30, PaCO2: 15 mmHg, HCO3-: 16 mEq/L

12%

(2/16)

2

pH: 7.31, PaCO2: 31 mmHg, HCO3-: 15 mEq/L

31%

(5/16)

3

pH: 7.37, PaCO2: 41 mmHg, HCO3-: 12 mEq/L

25%

(4/16)

4

pH: 7.41, PaCO2: 65 mmHg, HCO3-: 34 mEq/L

19%

(3/16)

5

pH: 7.47, PaCO2: 11 mmHg, HCO3-: 24 mEq/L

6%

(1/16)

M 6 E

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