What are some commonly used opioids for pain management?

Commonly Used Opioids for Pain Management

Morphine, oxycodone, hydromorphone, and fentanyl are the most commonly used opioids for pain management, with morphine being the standard first-choice opioid for moderate to severe pain. 1

Classification of Opioids by Pain Intensity

Mild to Moderate Pain (WHO Step II)

• Codeine (tablets 15-30-60 mg, duration 4-6 hours, max daily dose 360 mg) 1
• Tramadol (capsules 50 mg or drops 100 mg/ml, duration 2-4 hours, max daily dose 400 mg) 1
• Dihydrocodeine (modified-release tablets 60-90-120 mg, duration 12 hours, max daily dose 240 mg) 1

Moderate to Severe Pain (WHO Step III)

• Morphine (oral and parenteral forms, considered gold standard, no upper dose limit) 1
• Oxycodone (oral, 1.5-2 times more potent than oral morphine) 1
• Hydromorphone (oral, 7.5 times more potent than oral morphine) 1
• Fentanyl (transdermal, 4 times more potent than oral morphine) 1
• Methadone (oral, 4-12 times more potent than oral morphine depending on dose) 1
• Buprenorphine (oral and transdermal forms) 1

First-Line Opioid Selection

• Oral morphine is the opioid of first choice for moderate to severe cancer pain due to its effectiveness, tolerability, simple administration, and low cost 1
• For patients with severe pain requiring urgent relief, parenteral opioids (intravenous or subcutaneous) are recommended 1
• The relative potency ratio of oral to parenteral morphine is between 1:2 and 1:3 1

Special Considerations for Specific Opioids

Morphine

• Standard starting drug for opioid-naïve patients 1
• Initial oral dose of 5-15 mg or 2-5 mg IV for opioid-naïve patients 1
• Should be avoided in patients with renal disease and hepatic insufficiency due to accumulation of active metabolite morphine-6-glucuronide 1

Methadone

• More complicated to use due to marked inter-individual differences in plasma half-life and duration of action 1
• Should be initiated only by physicians with experience and expertise in its use 1
• Requires careful titration due to long half-life (8 to >120 hours) 1

Fentanyl

• Transdermal fentanyl is not indicated for rapid opioid titration 1
• Should only be used after pain is controlled by other opioids 1
• Conversion from IV to transdermal fentanyl can use a 1:1 conversion ratio 1

Not Recommended Opioids

• Mixed agonist-antagonists (butorphanol, pentazocine) 1
• Propoxyphene (contraindicated for chronic pain, especially with renal impairment) 1
• Meperidine (contraindicated for chronic pain due to neurotoxicity risk) 1

Clinical Pitfalls and Caveats

• Opioid selection should consider the patient's pain intensity, current analgesic therapy, and concomitant medical conditions 1
• Individual patients vary greatly in their response to different opioids, necessitating individualized approaches 1
• Opioids with short half-lives (morphine, hydromorphone, fentanyl, oxycodone) are preferred for titration compared to those with long half-lives (methadone, levorphanol) 1
• All opioids carry risks of tolerance, dependence, and potential for abuse 2, 3
• When switching between opioids, use caution with dose conversion as relative effectiveness varies considerably among patients 1
• For patients with refractory pain, opioid rotation may improve the therapeutic window and establish a more advantageous analgesia/toxicity relationship 1

By understanding the pharmacological properties, relative potencies, and specific considerations for each opioid, clinicians can make informed decisions to optimize pain management while minimizing adverse effects.