Pain Management Regimens

Comprehensive bedside reference for acute and chronic pain management in inpatient and outpatient settings, including pain classification, multimodal protocols, renal/hepatic dose adjustments, PCA management, and safety guidelines.

1. General Guidelines & Assessment

Assessment Scales

Numerical Rating Scale (NRS 0–10): Standard self-report scale for verbal adult patients (1–3 mild, 4–6 moderate, 7–10 severe).
Visual Analog Scale (VAS): 100 mm continuous line from “no pain” to “worst imaginable pain” (Bijur 2001).
FLACC Scale (Face, Legs, Activity, Cry, Consolability): Evaluates non-verbal or pediatric populations scored 0–10 (Merkel 1997).
CPOT (Critical Care Pain Observation Tool): Validated for intubated/non-verbal ICU patients, scored 0–8 assessing facial expression, body movement, muscle tension, and ventilator compliance (Gélinas 2006).

Multimodal Analgesia Principles

Combine non-opioid analgesics (acetaminophen, NSAIDs, gabapentinoids, topical agents) acting on distinct pain pathways with regional blocks and non-pharmacologic interventions (cold/heat therapy, physical therapy, TENS).
Goal: Achieve synergistic pain relief while significantly reducing cumulative opioid exposure and associated adverse effects (sedation, respiratory depression, ileus, hyperalgesia) (APS/ASRA/ASA Postoperative Pain Guideline 2016).

WHO Pain Relief Ladder

Step 1 (Mild Pain, NRS 1–3): Non-opioid (Acetaminophen, NSAID) ± adjuvant.
Step 2 (Moderate Pain, NRS 4–6): Non-opioid + short-acting mild opioid (Codeine, Tramadol) OR low-dose strong opioid ± adjuvant.
Step 3 (Severe Pain, NRS 7–10): Non-opioid + strong opioid (Morphine, Oxycodone, Hydromorphone, Fentanyl) ± adjuvant.
Step 4 (Severe/Refractory Pain): Interventional procedures (epidural, nerve blocks, intrathecal pump) ± systemic therapy (WHO 2018 Cancer Pain Guidelines).

Morphine Milligram Equivalents (MME) & CDC 2022 Guidelines

MME is a standardized measure for epidemiological surveillance, research, and population-level risk assessment. Do not use calculated MME doses to convert from one opioid to another; equianalgesic conversion requires accounting for incomplete cross-tolerance, individual pharmacokinetics, and clinical context that MME factors do not capture (CDC 2022 Guideline).

CDC 2022 Guideline Key Principles (CDC 2022 Guideline):
- Non-opioid therapies are at least as effective as opioids for many common types of acute pain and should be maximized first.
- When opioids are initiated for opioid-naive patients, prescribe the lowest effective dose of an immediate-release opioid for no longer than needed for the expected duration of pain severe enough to require opioids.
- Before increasing total opioid dosage to ≥ 50 MME/day, carefully evaluate individual benefits and risks. There is no single safe universal MME threshold; overdose risk increases progressively with dosage.
- Co-prescribe Naloxone for patients at increased risk of overdose (history of overdose, substance use disorder, MME ≥ 50, concurrent benzodiazepines, or sleep apnea).
- Excluded populations: This guideline does not apply to sickle cell disease pain, cancer-related pain treatment, palliative care, end-of-life care, children < 18 years, or hospitalized/ED patients (applies at discharge only).

Equianalgesic Opioid Conversion

Equianalgesic dose conversions are estimates only and cannot account for individual variability in genetics and pharmacokinetics. The ratios below are composite estimates derived from multiple clinical studies and manufacturer data (Treillet 2018). When converting from one opioid to another, the new opioid is typically dosed at a substantially lower dose than the calculated equianalgesic dose to avoid overdose because of incomplete cross-tolerance (Fine & Portenoy 2009; Treillet 2018).

Oral Morphine: 30 mg (reference standard)
Oral Oxycodone: 20 mg (approximately 1.5× oral morphine)
Oral Hydromorphone: 7.5 mg (approximately 4× oral morphine)
IV Morphine: 10 mg (approximately 3× oral morphine)
IV Hydromorphone: 1.5 mg (approximately 20× oral morphine)
IV Fentanyl: 100 mcg (approximately 300× oral morphine)

[!WARNING] Equianalgesic ratios are starting-point estimates only. Reduce the calculated dose of the new opioid by 25–50% to account for incomplete cross-tolerance, then titrate to effect. These ratios are not MME conversion factors and must not be used interchangeably with CDC MME values.

2. Pain Classification & Descriptors

Type of Pain	Pathophysiology	Common Descriptors	Clinical Examples	Primary Therapies
Nociceptive Somatic	Tissue damage activating somatic nociceptors (skin, muscle, bone, joints)	Sharp, aching, throbbing, tender, well-localized	Fractures, sprains, incisional surgical pain, osteoarthritis	Acetaminophen, NSAIDs, local anesthetics, opioids for severe acute pain
Nociceptive Visceral	Activation of nociceptors in internal organs or organ capsules	Dull, cramping, deep, colicky, poorly localized; often referred	Appendicitis, renal colic, biliary colic, bowel obstruction	Antispasmodics, NSAIDs (colic), opioids, visceral nerve block
Neuropathic	Primary lesion or dysfunction in peripheral or central nervous system	Burning, shooting, electric shock, lancinating, tingling (“pins & needles”), allodynia	Diabetic neuropathy, postherpetic neuralgia, radiculopathy, phantom limb	Gabapentinoids (Gabapentin, Pregabalin), SNRIs (Duloxetine), TCAs (Amitriptyline), Lidocaine 5% patch
Inflammatory	Immune/cytokine sensitization of primary afferent nociceptors	Swollen, warm, tender, throbbing, hyperalgesic	Rheumatoid arthritis, acute gout, cellulitis, inflammatory bowel disease	NSAIDs, Corticosteroids, disease-targeted biologics

Duration Classifications

Acute Pain: < 1 month duration; serves a protective biological warning function; directly linked to tissue injury.
Subacute Pain: 1 to 3 months duration.
Chronic Pain: > 3 months duration (or persisting beyond normal tissue healing time); recognized as an independent complex disease state.

3. Outpatient Pain Regimens

Acute Pain Protocols (Non-Opioid First Line)

Mild-to-Moderate Acute Pain (e.g., sprains, dental pain, minor surgical procedures):
- Acetaminophen: 650–1,000 mg PO q6h PRN (max 4,000 mg/day in healthy adults; 2,000–3,000 mg/day in elderly or mild hepatic impairment).
- NSAID: Ibuprofen 400–800 mg PO q6h with food (max 2,400–3,200 mg/day) OR Naproxen 250–500 mg PO q12h with food (max 1,000–1,250 mg/day).
- Synergy: Alternating or combining Acetaminophen + Ibuprofen provides superior analgesia to either monotherapy.
Severe Acute Pain (e.g., major fractures, acute surgical trauma):
- Scheduled non-opioid base (Acetaminophen + NSAID if not contraindicated).
- Add short-acting opioid for no longer than the expected duration of pain severe enough to require opioids. For many common causes of nonsurgical acute pain, a few days or less is often sufficient. Durations should be individualized to the patient’s clinical circumstances; severe traumatic injuries may require > 7 days (CDC Opioid Guideline 2022):
  - Oxycodone: 2.5–5 mg PO q4–6h PRN pain.
  - Hydrocodone/Acetaminophen (5/325 mg): 1 tab PO q4–6h PRN pain (count total daily acetaminophen).

Chronic Non-Cancer Pain Management

Non-Pharmacologic: Physical therapy, exercise therapy, cognitive behavioral therapy (CBT), acupuncture.
First-Line Pharmacologic:
- Neuropathic Pain: Duloxetine 30–60 mg PO daily OR Gabapentin 100–300 mg PO TID (titrated up to max 1,800–3,600 mg/day) OR Pregabalin 50–75 mg PO BID (titrated to 150–300 mg/day).
- Localized Pain: Lidocaine 5% patch (apply 12 hours on, 12 hours off) OR Topical NSAIDs (Diclofenac 1% gel 2–4 g QID).
Opioid Stewardship & Risk Mitigation:
- State PDMP check prior to prescribing.
- Urine Drug Screening (UDS) baseline and periodic.
- Co-prescribe Naloxone 4 mg nasal spray (1 spray in one nostril; repeat in 2–3 min in opposite nostril if no response).

4. Inpatient Pain Regimens

Multimodal Inpatient Acute Pain Protocol

Baseline Scheduled Non-Opioids:
- Acetaminophen 1,000 mg PO/IV q6h (max 4g/day).
- Ketorolac (IV NSAID) 15–30 mg IV q6h scheduled/PRN for max 5 days (reduce to 15 mg IV in age ≥ 65, weight < 50 kg, or renal impairment).
Breakthrough PRN Oral Opioids (NRS 4–6 Moderate):
- Oxycodone 5 mg PO q4h PRN pain.
Breakthrough PRN IV Opioids (NRS 7–10 Severe / NPO):
- Hydromorphone: 0.2–0.5 mg IV q2–3h PRN.
- Fentanyl: 25–50 mcg IV q1–2h PRN (short duration ~30–60 mins).
- Morphine: 2–4 mg IV q3–4h PRN.

Patient-Controlled Analgesia (PCA) Settings

Indicated for severe acute post-operative pain or oncology inpatients unable to take oral medications (APS/ASRA/ASA Postoperative Pain Guideline 2016).
Standard Opioid PCA Dosing Orders:

Drug	PCA Demand Dose	Lockout Interval	Continuous (Basal) Rate
Hydromorphone	0.1–0.2 mg	6–10 minutes	NONE (in opioid-naive) / 0.1–0.2 mg/hr (opioid-tolerant only)
Fentanyl	10–20 mcg	5–8 minutes	NONE (in opioid-naive) / 10–20 mcg/hr (opioid-tolerant only)
Morphine	0.5–1.5 mg	6–10 minutes	NONE (in opioid-naive) / 0.5–1.0 mg/hr (opioid-tolerant only)

[!WARNING] Basal (continuous) infusions on PCA should NEVER be ordered in opioid-naive patients due to high risk of severe hypoventilation and fatal overdose.

5. Renal Dosing Adjustments

In patients with Chronic Kidney Disease (CKD) or End-Stage Renal Disease (ESRD), renally-cleared parent drugs and active glucuronide metabolites accumulate, predisposing to severe neurotoxicity (myoclonus, hyperalgesia, seizures) and fatal respiratory depression (Pham 2009).

Opioid Renal Safety Tiers

Tier	Agent	Recommendation & CrCl Adjustment	Clinical Rationale & Toxicity
AVOID	Morphine	AVOID if CrCl < 30 mL/min and in ESRD / Dialysis	Accumulation of active metabolites Morphine-6-Glucuronide (M6G, potent CNS depressant) and Morphine-3-Glucuronide (M3G, neurotoxic). Causes severe sedation, respiratory depression, myoclonus, and seizures.
AVOID	Codeine	AVOID if CrCl < 30 mL/min	Active metabolites accumulate unpredictably; high risk of fatal narcosis.
CAUTION	Hydromorphone	Reduce dose 25–50%; extend interval. CrCl 10–50: 75% of dose; CrCl < 10: 50% of dose.	Hydromorphone-3-glucuronide (H3G) accumulates in renal failure (causes neuroexcitation/myoclonus), but lacks M6G respiratory depressant metabolite. Safer than morphine if monitored closely.
CAUTION	Oxycodone	Reduce dose 25–50%; extend interval. CrCl < 30: reduce initial dose by 50%.	Active metabolites accumulate; prolonged elimination half-life.
PREFERRED	Fentanyl	PREFERRED in severe renal impairment & ESRD/Dialysis.	Inactivated by liver (CYP3A4) into inactive norfentanyl; no active renal metabolites. High protein binding; not dialyzable.
PREFERRED	Methadone	PREFERRED in ESRD under specialist supervision.	Eliminated via fecal route; no active metabolites. Does not require renal dose reduction (caution: complex pharmacokinetics/QTc risk).
PREFERRED	Buprenorphine	PREFERRED option in renal failure.	Hepatic elimination (CYP3A4/glucuronidation); minimal active renal metabolites.

Non-Opioid Renal Adjustments

Acetaminophen: Safe in CKD/ESRD. Extend dosing interval to q6–8h for CrCl < 10 mL/min.
NSAIDs: Contraindicated in CKD Stage 4/5 (CrCl < 30 mL/min) and acute kidney injury (AKI). Causes renal vasoconstriction via prostaglandin inhibition, precipitating acute renal failure, fluid retention, and severe hyperkalemia.

6. Hepatic Dosing Adjustments

Hepatic impairment alters opioid clearance, first-pass metabolism (increasing oral bioavailability up to 100%), plasma protein binding (higher free drug fraction), and susceptibility to hepatic encephalopathy (Chandok 2010).

Non-Opioid Hepatic Adjustments

Acetaminophen: First-line non-opioid in cirrhosis/hepatic impairment. Cap maximum dose at 2,000 mg (2 g) per day. Avoid in active heavy alcohol abuse or severe acute hepatitis.
NSAIDs: Contraindicated in cirrhosis (Child-Pugh A/B/C). Impairs renal autoregulation leading to hepatorenal syndrome, blunts diuretic efficacy, and causes severe gastrointestinal ulceration/variceal bleeding.

Opioid Hepatic Adjustments (Child-Pugh Scoring)

Agent	Hepatic Metabolism & Safety	Dosing Adjustment in Cirrhosis
Fentanyl	PREFERRED. Short half-life, no active metabolites. Minimal effect from mild-moderate cirrhosis.	Titrate carefully; reduce dose frequency in severe hepatic failure (Child-Pugh C).
Hydromorphone	PREFERRED. Metabolized via Phase II glucuronidation (relatively preserved in liver disease).	Start at 50% lower initial dose; extend dosing interval (q6–8h).
Morphine	Use with caution. First-pass metabolism decreased (bioavailability doubles from 30% to 60%). Half-life prolonged.	Reduce dose by 50% and double interval. High risk of precipitating hepatic encephalopathy.
Oxycodone	Use with caution. Decreased CYP clearance. Bioavailability increases.	Reduce initial dose by 30–50%; extend interval.
Codeine / Tramadol	CONTRAINDICATED / AVOID. Requires hepatic CYP2D6 conversion to active metabolites (M1/Morphine). Unpredictable response.	Avoid in hepatic dysfunction.

7. Special Considerations & Safety

Opioid-Induced Constipation (OIC) Bowel Regimen

Opioids inhibit gastrointestinal motility and secretions. Tolerance to constipation does NOT develop over time.
Mandatory Co-Prescription upon Opioid Initiation:
- First-Line: Stimulant laxative (Senna 1–2 tabs PO daily to BID) + Stool Softener (Docusate 100 mg PO BID) OR Osmotic Laxative (Polyethylene Glycol 3350 17 g PO daily).
- Refractory OIC: Peripherally Acting Mu-Opioid Receptor Antagonists (PAMORAs) e.g. Methylnaltrexone 12 mg SQ daily or Naldemedine 0.2 mg PO daily.

Pasero Opioid-Induced Sedation Scale (POSS)

Monitoring sedation is critical to preventing opioid-induced respiratory depression (Pasero 2009).

S: Sleeping, easy to arouse. (Acceptable; no action needed).
1: Awake and alert. (Acceptable; no action needed).
2: Slightly drowsy, easily aroused. (Acceptable; no action needed).
3: Frequently drowsy, arousable, drifts off to sleep during conversation. (UNACCEPTABLE; decrease opioid dose by 25–50% or increase interval; notify provider).
4: Somnolent, minimal or no response to verbal/physical stimulation. (UNACCEPTABLE; stop opioid; consider Naloxone; stay with patient and call emergency team).

Emergency Naloxone Reversal Protocol

Indication: Opioid overdose with respiratory depression (RR < 8–10 breaths/min, oxygen saturation < 90%, unarousable).
Inpatient IV Protocol:
- Dilute Naloxone 0.4 mg in 9 mL NS (40 mcg/mL). Give 40–80 mcg IV q2 minutes titrated to adequate ventilation (goal is RR > 10 without triggering acute severe opioid withdrawal/pain crisis).
Outpatient Nasal Spray:
- Naloxone 4 mg single-dose nasal spray: Administer 1 spray into one nostril. If no response in 2–3 minutes, administer second spray in opposite nostril and call 911.

8. References & Evidence Base

CDC Clinical Practice Guideline for Prescribing Opioids for Pain (2022). MMWR Recomm Rep 2022;71(No. RR-3):1–95. CDC Opioid Prescribing Guideline (PMID 36327391).
American Pain Society, American Society of Regional Anesthesia and Pain Medicine, American Society of Anesthesiologists. Management of Postoperative Pain: A Clinical Practice Guideline. J Pain. 2016;17(2):131-157. APS/ASRA/ASA Guideline (PMID 26827847).
Treillet E, Laurent S, Hadjiat Y. Practical management of opioid rotation and equianalgesia. J Pain Res. 2018;11:2587-2601. Treillet 2018 (PMID 30464578).
Fine PG, Portenoy RK. Establishing “best practices” for opioid rotation: conclusions of an expert panel. J Pain Symptom Manage. 2009;38(3):418-425. Fine & Portenoy 2009 (PMID 19735902).
FLACC Behavioral Pain Scale Validation. Pediatr Nurs. 1997;23(3):293-297. FLACC Validation (PMID 9220806).
Critical-Care Pain Observation Tool (CPOT) Validation. Am J Crit Care. 2006;15(4):420-427. CPOT Validation (PMID 16823021).
Visual Analog Scale (VAS) Reliability. Acad Emerg Med. 2001;8(12):1153-1157. VAS Reliability (PMID 11733257).
Pasero Sedation Scale (POSS). J PeriAnesth Nurs. 2009;24(5):286-290. Pasero 2009 (PMID 19800534).
Pain Management in Chronic Kidney Disease. Clin J Am Soc Nephrol. 2009;4(8):1452-1459. Pham 2009 (PMID 19692600).
Pain Management in Cirrhosis. Hepatology. 2010;52(4):1488-1497. Chandok 2010 (PMID 20857418).