What are the different types of pain killer medications?

Different Types of Pain Killer Medications

Pain killer medications are categorized into three main classes based on the WHO analgesic ladder: non-opioid analgesics for mild pain, weak opioids for moderate pain, and strong opioids for moderate to severe pain. 1

Non-Opioid Analgesics (WHO Level 1)

These medications are recommended for mild to moderate pain and can be combined with opioid analgesics when necessary:

• Acetaminophen (Paracetamol): Recommended as first-line treatment for mild to moderate pain at doses of 1g every 4-6 hours (maximum 4g/day). Use cautiously in patients with liver failure. 1

• Nonsteroidal Anti-Inflammatory Drugs (NSAIDs):

  • Particularly effective for inflammatory pain, especially bone pain 1
  • Common options include ibuprofen, ketoprofen, diclofenac, naproxen 1
  • Caution with gastrointestinal, renal, and cardiovascular side effects 1, 2
  • COX-2 inhibitors (e.g., celecoxib) have improved GI safety but increased cardiovascular risk 1, 2

• Topical Analgesics: Useful for localized pain areas, including lidocaine, salicylate, and capsaicin 1, 3

Weak Opioids (WHO Level 2)

These medications are indicated for moderate pain that doesn't respond to non-opioid analgesics:

• Codeine: Often combined with acetaminophen, requires monitoring for constipation 1

• Tramadol: Effective for moderate pain, but use with caution in patients with epilepsy risk or those taking antidepressants 1

• Dihydrocodeine: Available in immediate and modified-release formulations 1

• Low-dose strong opioids: Can be considered as an alternative to weak opioids 1

Strong Opioids (WHO Level 3)

Reserved for moderate to severe pain when other options are insufficient:

• Morphine: First-line choice for moderate to severe pain, available in immediate and sustained-release formulations 1, 4

• Oxycodone: Approximately 1.5-2 times as potent as oral morphine 5

• Hydromorphone: Effective alternative to oral morphine 1

• Fentanyl: Best reserved for patients with stable opioid requirements, particularly useful in transdermal form for patients unable to swallow or with poor tolerance to morphine 1, 4

• Methadone: Alternative option but more complicated to use due to inter-individual differences in half-life; should be initiated only by experienced physicians 1, 4

• Buprenorphine: Useful option, particularly in transdermal form 1

Adjuvant Medications

These medications can enhance pain control when used alongside primary analgesics:

• Antidepressants: Including tricyclic antidepressants (TCAs), SSRIs, and SNRIs, which enhance monoaminergic neurotransmission 1, 6

• Anticonvulsants: Gabapentin and pregabalin are first-line for neuropathic pain, working by binding to calcium channels 1

• Muscle Relaxants: Useful for pain with muscle spasm component 1, 6

Clinical Approach to Pain Management

1. For mild pain: Start with acetaminophen or NSAIDs based on pain type and patient risk factors 7, 8

2. For moderate pain: Add weak opioids (codeine, tramadol) or low-dose strong opioids if non-opioids are insufficient 1

3. For severe pain: Use strong opioids, preferably starting with oral morphine unless urgent relief is needed (then use parenteral administration) 1

4. For breakthrough pain: Provide immediate-release formulations at approximately 10% of the total daily opioid dose 5

Important Considerations

• Multimodal analgesia combining different medication classes can improve pain control while reducing side effects of individual drugs 1

• Regular administration rather than "as needed" dosing is recommended for chronic pain 1

• Oral route should be preferred when possible 1

• Monitor for side effects: Opioids commonly cause constipation, nausea, somnolence, and risk of dependence; NSAIDs can cause GI, renal, and cardiovascular complications 2

• In renal impairment: All opioids should be used with caution at reduced doses; fentanyl and buprenorphine are safer choices in advanced kidney disease 1