UNIT 9: ANALGESICS (Part 2) - OPIOIDS, OPIOID SUBSTITUTES, AND OPIOID ANTAGONISTS

• Morphine
• Methadone
• Fentanyl
• Hydromorphone, oxymorphone
• Meperidine
• Oxycodone
• Sufentanil, alfentanil, remifentanil
• Codeine
• Hydrocodone

OPIOID AGONISTS:

OPIOID AGONISTS

Morphine

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Methadone

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Fentanyl

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Hydromorphone, oxymorphone

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Meperidine

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Oxycodone

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Sufentanil, alfentanil, remifentanil

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Codeine

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

OPIOID AGONISTS

Hydrocodone

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

• Morphine
• Methadone
• Fentanyl

MECHANISM OF ACTION:
• Strong µreceptor agonists
• Variable affinity for delta and kappa receptors

• Morphine
• Methadone
• Fentanyl

EFFECTS:
• Analgesia
• Relief of anxiety
• Sedation
• Slowed gastrointestinal transit

• Morphine
• Methadone
• Fentanyl

CLINICAL APPLICATIONS:
• Severe pain
• Adjunct in anesthesia (fentanyl, morphine)
• Pulmonary edema (morphine only)
• Maintenance in rehabilitation programs (methadone only)

• Morphine
• Methadone
• Fentanyl

PHARMACOKINETICS, TOXICITIES:
• First-pass effect
• Duration 1-4 h except methadone, 4-6 h
• Toxicity: respiratory depression,
• Severe constipation,
• Addiction liability,
• Convulsions

Hydromorphone, oxymorphone

Like morphine in efficacy, but higher potency

Meperidine

Strong agonist with anticholinergic effects

Oxycodone

Dose-dependent analgesia

Sufentanil, alfentanil, remifentanil

Like fentanyl but shorter duration of action

• Codeine
• Hydrocodone

MECHANISM OF ACTION:
• Less efficacious than morphine
• Can antagonize strong agonists

• Codeine
• Hydrocodone

EFFECTS:
• Like strong agonists
• Weaker effects

• Codeine
• Hydrocodone

CLINICAL APPLICATIONS:
• Mild-moderate pain
• Cough (codeine)

• Codeine
• Hydrocodone

PHARMACOKINETICS, TOXICITIES:
• Like strong agonists, toxicity dependent on genetic variation of metabolism

• Buprenorphine
• Nalbuphine

MIXED OPIOID AGONIST-ANTAGONISTS:

MIXED OPIOID AGONIST-ANTAGONISTS

Buprenorphine

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

Buprenorphine

MECHANISM ACTION:
• Partial µ agonist
• K antagonist

Nalbuphine

(OPIOID AGONISTS / MIXED OPIOID AGONIST-ANTAGONISTS)

Buprenorphine

EFFECTS:
• Like strong agonists but can antagonize their effects
• Also reduces craving for alcohol

Buprenorphine

CLINICAL APPLICATIONS:
• Moderate pain
• Some maintenance rehabilitation programs

Buprenorphine

PHARMACOKINETICS, TOXICITIES:
• Long duration of action 4-8 h
• May precipitate abstinence syndrome

Nalbuphine

MECHANISM ACTION:
• K agonist • µ antagonist

Nalbuphine

EFFECTS:
• Similar to buprenorphine

Nalbuphine

CLINICAL APPLICATIONS:
• Moderate pain

Nalbuphine

PHARMACOKINETICS, TOXICITIES:
• Like buprenorphine