Opioid Conversions & Pain Management

Opioid Conversions & Pain Management

Master opioid conversions and pain management strategies with free flashcards and spaced repetition practice. This lesson covers equianalgesic dosing, opioid rotation techniques, patient-specific conversion factors, and high-alert medication safety—essential knowledge for NAPLEX success and safe clinical practice.

Welcome to Opioid Conversions & Pain Management 💊

Opioid conversions represent one of the most critical—and potentially dangerous—calculations pharmacists perform. A miscalculation can lead to severe respiratory depression, overdose, or inadequate pain control. This lesson equips you with systematic approaches to:

• Convert between different opioid formulations using equianalgesic ratios
• Apply safety principles to minimize conversion-related adverse events
• Recognize special populations requiring dose adjustments
• Implement multimodal pain management strategies

Whether you're rotating opioids due to tolerance, managing side effects, or transitioning between routes of administration, precision and caution are paramount. Let's build your confidence with this high-stakes clinical skill.

---

Core Concepts: Understanding Equianalgesic Dosing 🔢

What is Equianalgesic Dosing?

Equianalgesic dosing refers to doses of different opioids that provide approximately equal analgesic effects. Because opioids vary in potency, receptor affinity, and bioavailability, we use conversion ratios to switch between agents safely.

💡 Key Principle: These are approximate conversions. Individual patient responses vary based on genetics (CYP450 polymorphisms), tolerance, renal/hepatic function, and concurrent medications.

Standard Equianalgesic Table

Opioid	Oral Dose (mg)	Parenteral Dose (mg)	Conversion Factor vs Morphine PO
Morphine	30	10	1 (reference)
Oxycodone	20	—	1.5
Hydrocodone	30	—	1
Hydromorphone	7.5	1.5	4
Fentanyl (transdermal)	—	—	See special calculation*
Methadone	Variable**	—	Variable (see below)
Codeine	200	—	0.15
Tramadol	300	—	0.1

*Fentanyl transdermal: For every 2 mg/24h of oral morphine equivalent, use approximately 1 mcg/h patch

**Methadone dosing is non-linear and requires special consideration (see below)

The Conversion Process: Step-by-Step 📋

┌─────────────────────────────────────────────────┐
│         OPIOID CONVERSION WORKFLOW              │
└─────────────────────────────────────────────────┘

    📊 Step 1: Calculate Total Daily Dose
           |
           ↓
    🔄 Step 2: Convert to Morphine Equivalents
           |
           ↓
    🎯 Step 3: Apply Conversion Ratio
           |
           ↓
    ⚠️ Step 4: Apply Safety Reduction (25-50%)
           |
           ↓
    📝 Step 5: Divide into Dosing Schedule
           |
           ↓
    👀 Step 6: Monitor & Titrate

Step 1: Calculate Total Daily Dose (TDD)

Sum all opioid doses the patient receives in 24 hours, including scheduled and PRN (as-needed) doses actually taken.

Step 2: Convert to Oral Morphine Equivalents (OME)

This creates a common denominator for comparison.

Formula:

OME = Current daily dose × Conversion factor

Step 3: Apply Conversion Ratio to New Opioid

New opioid dose = OME ÷ New opioid conversion factor

Step 4: Apply Safety Reduction ⚠️

CRITICAL: Reduce the calculated dose by 25-50% to account for:

• Incomplete cross-tolerance between opioids
• Individual variability in metabolism
• Prevention of overdose from calculation errors

Safe starting dose = Calculated dose × 0.5 to 0.75

💡 Use 50% reduction when:

• Elderly patients (≥65 years)
• Renal/hepatic impairment
• Opioid-naive or low tolerance
• High-risk medications (methadone, fentanyl)

💡 Use 25% reduction when:

• Younger, healthier patients
• Well-documented tolerance
• Conversion between similar opioids

Step 5: Divide into Dosing Schedule

For immediate-release: Divide by 4-6 for q4-6h dosing For extended-release: Divide by 2 for q12h or keep total for q24h

Step 6: Monitor & Titrate

Reassess pain and side effects within 24-72 hours. Adjust by 25-50% increments as needed.

---

Special Considerations: High-Risk Conversions ⚠️

Methadone: The Tricky One 🎭

Methadone is unique due to:

• Non-linear pharmacokinetics: Higher OME doses require proportionally less methadone
• Long half-life: 8-59 hours (average 24h) leading to accumulation risk
• QTc prolongation: Risk of torsades de pointes
• NMDA receptor antagonism: Additional pain-modulating effects

Methadone Conversion Table (OME to Methadone)

Current OME (mg/day)	Conversion Ratio (OME:Methadone)	Example
≤100	3:1	90 mg OME → 30 mg methadone/day
101-300	5:1	200 mg OME → 40 mg methadone/day
301-600	10:1	500 mg OME → 50 mg methadone/day
>600	12:1	720 mg OME → 60 mg methadone/day

⚠️ Methadone Safety Pearls:

• Start LOW and titrate SLOWLY (no more frequently than every 5-7 days)
• Maximum recommended starting dose: 30-40 mg/day in divided doses
• Obtain baseline ECG and monitor QTc interval
• Counsel patients on delayed onset of peak effect (3-5 days)
• Be extra cautious with CYP3A4 inhibitors (fluconazole, macrolides)

Fentanyl Transdermal: The Potent Patch 🩹

Fentanyl is 50-100× more potent than morphine.

Conversion Formula:

Fentanyl patch (mcg/h) = OME (mg/day) ÷ 2

Example: Patient on 120 mg OME/day

120 mg ÷ 2 = 60 mcg/h patch

⚠️ Fentanyl Patch Safety:

• Only for opioid-tolerant patients: FDA requires ≥60 mg OME/day × 7 days
• Delayed onset: Takes 12-24h to reach therapeutic levels
• Delayed offset: Continue for 12-24h after removal
• Heat warning: Fever or external heat sources increase absorption
• Provide breakthrough pain medication during initiation

🔥 Did you know? Fentanyl patches were originally developed for cancer pain management and are contraindicated for acute pain or postoperative use due to their pharmacokinetic profile.

Hydromorphone: The Concentration Concern 💉

Hydromorphone is 4-5× more potent than morphine orally and 5-7× more potent parenterally.

⚠️ Common Error: Confusing hydromorphone with morphine leads to 5× overdoses. Always double-check the drug name!

Oral to IV Hydromorphone: 5:1 ratio

• 7.5 mg PO hydromorphone ≈ 1.5 mg IV hydromorphone

---

Worked Examples: Mastering the Math 🧮

Example 1: Simple Opioid Rotation (Morphine to Oxycodone)

Clinical Scenario: Patient currently takes morphine IR 15 mg PO q4h (6 doses daily) for chronic back pain. Due to persistent nausea, the physician wants to rotate to oxycodone. Calculate the new dose.

Solution:

Step	Calculation	Result
1. Calculate current TDD	15 mg × 6 doses	90 mg morphine/day
2. Already in OME	Morphine is reference	90 mg OME
3. Convert to oxycodone	90 mg ÷ 1.5	60 mg oxycodone/day
4. Apply 25% reduction	60 mg × 0.75	45 mg oxycodone/day
5. Divide for dosing	45 mg ÷ 6 doses	7.5 mg q4h

Answer: Oxycodone IR 7.5 mg PO q4h

Clinical Pearl: Since oxycodone typically causes less nausea than morphine (no active metabolite accumulation), this rotation may resolve the patient's issue. Monitor for 24-48 hours.

---

Example 2: IV to PO Conversion with Route Change

Clinical Scenario: Postoperative patient receiving morphine 2 mg IV q3h (8 doses daily) via PCA. Ready for discharge on oral oxycodone. Calculate appropriate dose.

Solution:

Step	Calculation	Result
1. Calculate current TDD	2 mg × 8 doses	16 mg morphine IV/day
2. Convert IV to PO morphine	16 mg × 3 (IV:PO ratio)	48 mg OME
3. Convert to oxycodone	48 mg ÷ 1.5	32 mg oxycodone/day
4. Apply 25% reduction	32 mg × 0.75	24 mg oxycodone/day
5. Divide for dosing	24 mg ÷ 6 doses (q4h)	4 mg q4h

Answer: Oxycodone IR 5 mg PO q4h PRN (round to commercially available strength)

Clinical Pearl: For postoperative pain transitioning to oral therapy, using PRN dosing allows patient-controlled tapering as surgical pain resolves. Provide clear instructions on maximum daily dose.

---

Example 3: Complex Multi-Opioid Conversion to Fentanyl Patch

Clinical Scenario: 67-year-old patient with cancer pain currently on:

• Morphine ER 60 mg PO q12h
• Morphine IR 15 mg PO q4h PRN (takes 4 doses daily)

Physician wants to convert to fentanyl transdermal for improved compliance. Calculate patch strength.

Solution:

Step	Calculation	Result
1. Calculate scheduled TDD	60 mg × 2	120 mg morphine ER
2. Calculate PRN usage	15 mg × 4	60 mg morphine IR
3. Total OME	120 + 60	180 mg OME/day
4. Convert to fentanyl	180 mg ÷ 2	90 mcg/h
5. Apply 50% reduction (elderly)	90 × 0.5	45 mcg/h

Answer: Fentanyl patch 50 mcg/h q72h (round to available strength)

PLUS: Provide breakthrough medication:

• Calculate 10-15% of TDD as breakthrough dose
• 180 mg × 0.10 = 18 mg OME ≈ Morphine IR 15 mg PO q2h PRN

Clinical Pearls:

• Do not apply first patch until morning after last ER morphine dose to avoid overlap
• Instruct patient to continue IR morphine for first 12-24 hours after patch application
• Patient is opioid-tolerant (≥180 mg OME/day), making fentanyl patch appropriate
• Re-assess in 72 hours (one patch cycle) before adjusting

---

Example 4: Methadone Conversion for High-Dose Opioid

Clinical Scenario: Patient with severe chronic pain on:

• Oxycodone ER 80 mg PO q12h
• Oxycodone IR 20 mg PO q4h PRN (takes 6 doses daily)

Due to tolerance and escalating doses, rotate to methadone. Calculate starting dose.

Solution:

Step	Calculation	Result
1. Calculate oxycodone TDD	(80×2) + (20×6)	280 mg oxycodone/day
2. Convert to OME	280 mg × 1.5	420 mg OME/day
3. Apply methadone ratio	420 mg ÷ 10 (301-600 range)	42 mg methadone/day
4. Apply 50% reduction	42 mg × 0.5	21 mg methadone/day
5. Divide for TID dosing	21 mg ÷ 3	7 mg TID

Answer: Methadone 5 mg PO TID (round down for safety) with close monitoring

Critical Safety Measures: ✅ Obtain baseline ECG (check QTc) ✅ Counsel on slow onset (don't take extra doses) ✅ Provide short-acting opioid for breakthrough (e.g., oxycodone IR 10 mg q4h PRN) ✅ No titration for 5-7 days (allow steady state) ✅ Naloxone kit and education

⚠️ Did you know? Methadone's unpredictable pharmacokinetics mean some patients may need BID dosing while others require TID or even QID to maintain consistent analgesia.

---

Common Mistakes to Avoid ⚠️

1. Forgetting the Safety Reduction 🚫

❌ Wrong: Calculating exact equianalgesic dose without reduction ✅ Right: Always reduce by 25-50% to account for incomplete cross-tolerance

Why it matters: Full equianalgesic conversions can cause respiratory depression due to individual variability.

---

2. Confusing Drug Names 🚫

❌ Wrong: Using morphine dose for hydromorphone (5× overdose risk!) ✅ Right: Always verify drug name, strength, and route before calculating

High-alert pairs:

• HYDROmorphone vs. morphine
• OxyCODONE vs. oxyCONTIN vs. oxyMORphone
• FentaNYL vs. SUFentanil

💡 Tip: Use tall-man lettering and always say the full drug name aloud.

---

3. Not Accounting for Route Changes 🚫

❌ Wrong: Converting oral morphine to IV morphine 1:1 ✅ Right: Applying 3:1 ratio (oral requires 3× more than IV)

Common ratios:

• Morphine oral:IV = 3:1
• Hydromorphone oral:IV = 5:1
• Oxycodone has no IV formulation in US

---

4. Using Fentanyl Patches in Opioid-Naive Patients 🚫

❌ Wrong: Starting 25 mcg/h patch for moderate acute pain ✅ Right: Fentanyl patches only for opioid-tolerant patients (≥60 mg OME/day × 7 days)

FDA Black Box Warning: Deaths have occurred from inappropriate use in opioid-naive patients.

---

5. Rapid Methadone Titration 🚫

❌ Wrong: Increasing methadone dose after 24-48 hours due to inadequate pain control ✅ Right: Waiting 5-7 days between adjustments (long half-life causes delayed accumulation)

What happens: Stacking doses before steady state → accumulation → respiratory depression days later

---

6. Ignoring Renal Function with Morphine 🚫

❌ Wrong: Standard morphine dosing in patient with CrCl <30 mL/min ✅ Right: Morphine metabolites (M3G, M6G) accumulate in renal impairment → choose alternative (oxycodone, hydromorphone, fentanyl)

Better choices for renal impairment:

• Fentanyl (no active metabolites)
• Hydromorphone (minimal renal accumulation)
• Avoid: Morphine, codeine, tramadol, meperidine

---

7. Forgetting Breakthrough Medication 🚫

❌ Wrong: Converting to long-acting only without immediate-release rescue ✅ Right: Always provide IR opioid for breakthrough pain (10-15% of TDD)

Example: Patient on fentanyl 50 mcg/h patch:

• Equivalent to ~100 mg OME/day
• Breakthrough: Morphine IR 10-15 mg q2h PRN

---

8. Not Documenting PRN Usage 🚫

❌ Wrong: Converting based only on scheduled doses ✅ Right: Reviewing medication administration records for actual PRN consumption

Why it matters: Patient taking oxycodone IR "q4h PRN" might use 2 doses or 6 doses daily—vastly different TDD!

---

Multimodal Pain Management: Beyond Opioids 🎯

Effective pain control often requires multimodal analgesia—combining medications with different mechanisms of action to improve efficacy while reducing opioid requirements.

The WHO Pain Ladder (Modified)

┌─────────────────────────────────────┐
│  Step 3: SEVERE PAIN                │
│  Strong opioid ± non-opioid         │
│  ± adjuvant                         │
│  (morphine, fentanyl, methadone)    │
├─────────────────────────────────────┤
         ↑
┌─────────────────────────────────────┐
│  Step 2: MODERATE PAIN              │
│  Weak opioid + non-opioid           │
│  ± adjuvant                         │
│  (codeine, tramadol, hydrocodone)   │
├─────────────────────────────────────┤
         ↑
┌─────────────────────────────────────┐
│  Step 1: MILD PAIN                  │
│  Non-opioid ± adjuvant              │
│  (acetaminophen, NSAIDs)            │
└─────────────────────────────────────┘

Key Non-Opioid Analgesics

Class	Examples	Mechanism	Best For
Acetaminophen	Tylenol	Central COX inhibition	Mild pain, fever, opioid-sparing
NSAIDs	Ibuprofen, naproxen, ketorolac	Peripheral COX inhibition	Inflammatory pain, bone pain
Gabapentinoids	Gabapentin, pregabalin	α2δ calcium channel blockade	Neuropathic pain
SNRIs	Duloxetine, venlafaxine	Serotonin/NE reuptake inhibition	Neuropathic pain, fibromyalgia
TCAs	Amitriptyline, nortriptyline	Multiple mechanisms	Neuropathic pain, headache
Topicals	Lidocaine patch, diclofenac gel	Local sodium channel/COX block	Localized pain
Muscle Relaxants	Cyclobenzaprine, tizanidine	Central α2 agonism	Musculoskeletal pain, spasm

Synergistic Combinations 🤝

Example Regimen for Postoperative Pain:

• Scheduled: Acetaminophen 1000 mg PO q6h + Ibuprofen 600 mg PO q6h (stagger q3h)
• Breakthrough: Oxycodone 5 mg PO q4h PRN
• Adjuvant: Gabapentin 300 mg PO TID (if neuropathic component)

💡 Opioid-sparing effect: This combination can reduce opioid requirements by 30-50%!

Special Population Considerations 👥

Elderly (≥65 years):

• ↓ Start low, go slow (50% dose reduction)
• ↑ Fall risk with CNS depressants
• ↓ Avoid long-acting opioids initially
• Consider constipation prophylaxis (all opioids cause this)

Renal Impairment (CrCl <30):

• ✅ Prefer: Fentanyl, hydromorphone, oxycodone
• ❌ Avoid: Morphine, codeine, tramadol, meperidine
• Adjust doses and monitor closely

Hepatic Impairment:

• All opioids metabolized hepatically
• Start with 50% dose reduction
• Avoid tramadol (seizure risk increases)
• Monitor for encephalopathy

Pregnancy:

• Opioids cross placenta
• Chronic use → neonatal abstinence syndrome
• Preferred if needed: Morphine, oxycodone (more data)
• Avoid: Codeine (variable metabolism), tramadol (limited data)

---

Safety Monitoring & Risk Mitigation 🛡️

REMS Program Requirements

The FDA requires a Risk Evaluation and Mitigation Strategy (REMS) for extended-release/long-acting (ER/LA) opioids:

✅ Prescriber training on proper patient selection ✅ Patient counseling documents ✅ Patient-Prescriber Agreement (PPA) ✅ Urine drug screening protocols ✅ Prescription Drug Monitoring Program (PDMP) checks

Naloxone Co-Prescribing 💉

Indications for naloxone kit:

• Opioid dose ≥50 mg OME/day
• Concurrent benzodiazepines or other CNS depressants
• History of substance use disorder
• Conditions increasing overdose risk (sleep apnea, COPD)
• History of overdose

Naloxone options:

• Nasal spray (Narcan®): 4 mg/spray, easiest for laypeople
• Auto-injector (Evzio®): 2 mg IM, audio instructions
• Injectable (generic): 0.4 mg/mL, requires training

Patient education: "If someone can't wake you up or you're not breathing normally, they should:

1. Call 911 immediately
2. Give naloxone (nasal or injection)
3. Perform rescue breathing if trained
4. Give second dose after 2-3 minutes if no response
5. Stay until EMS arrives"

Signs of Opioid Overdose 🚨

Classic Triad:

1. Pinpoint pupils (miosis)
2. Respiratory depression (<12 breaths/min)
3. Decreased consciousness (unresponsive)

Other signs:

• Cyanosis (blue lips/nails)
• Cold, clammy skin
• Choking/gurgling sounds
• Limp body

Tapering Opioids Safely 📉

When discontinuing chronic opioid therapy:

Taper schedule:

• General: ↓ 10% of original dose per week
• Rapid taper: ↓ 10% every few days (if safety concern)
• Slow taper: ↓ 10% every 2-4 weeks (long-term, high-dose)

Withdrawal symptoms (not dangerous but uncomfortable):

• Anxiety, irritability
• Muscle aches, joint pain
• Nausea, vomiting, diarrhea
• Lacrimation, rhinorrhea
• Diaphoresis, piloerection

Supportive management:

• Clonidine 0.1-0.2 mg q6h PRN (↓ sympathetic symptoms)
• Ondansetron 4-8 mg q8h PRN (nausea)
• Loperamide 2-4 mg q6h PRN (diarrhea)
• NSAIDs (muscle aches)

---

Key Takeaways 🎓

✅ Always reduce calculated conversions by 25-50% to account for incomplete cross-tolerance and individual variability

✅ The conversion process: TDD → OME → New opioid (÷ conversion factor) → Safety reduction → Dosing schedule

✅ High-risk conversions require extra caution:

• Methadone (non-linear, long half-life, QTc risk)
• Fentanyl (only for opioid-tolerant, delayed onset/offset)
• Hydromorphone (5× confusion risk with morphine)

✅ Special populations need dose adjustments:

• Elderly: 50% reduction
• Renal impairment: Avoid morphine, prefer fentanyl
• Hepatic impairment: 50% reduction, all opioids affected

✅ Multimodal analgesia reduces opioid requirements by 30-50%

✅ Provide breakthrough medication: 10-15% of TDD as immediate-release

✅ Monitor for safety: Naloxone co-prescribing, PDMP checks, urine drug screens, respiratory rate

✅ Document actual PRN usage when calculating conversions

✅ Never rush methadone: 5-7 days between dose adjustments

✅ Route matters: Oral requires 3× more morphine than IV

---

---

📚 Further Study

For additional information on opioid conversions and pain management:

1. CDC Opioid Prescribing Guideline: https://www.cdc.gov/opioids/healthcare-professionals/prescribing/guideline.html - Evidence-based recommendations for chronic pain management

2. FDA Opioid Analgesic REMS: https://www.fda.gov/drugs/information-drug-class/opioid-analgesic-risk-evaluation-and-mitigation-strategy-rems - Complete REMS program details and educational materials

3. ASPMN Opioid Conversion Reference: https://www.aspmn.org - American Society for Pain Management Nursing guidelines and clinical tools

---

🎯 You're now equipped to perform opioid conversions safely and effectively! Practice with various scenarios, always double-check your calculations, and remember: when in doubt, start low and titrate slowly. Patient safety is always the priority.