What are the various routes of opioid administration and names of opioids, particularly in a young to middle-aged adult patient with opioid dependence?

Routes of Opioid Administration and Common Opioid Names

Routes of Opioid Administration

Oral administration is the preferred and most common route for chronic opioid therapy due to its convenience and relatively steady blood concentrations. 1

Primary Routes of Administration

• Oral (PO): The first-choice route for patients who can swallow medications, providing steady plasma levels with onset in 30 minutes to 2 hours 1

• Intravenous (IV): Provides the fastest analgesia with peak effect at 15 minutes; recommended when rapid pain control is needed or when subcutaneous administration is contraindicated (peripheral edema, coagulation disorders, poor peripheral circulation) 1

• Subcutaneous (SC): Simple and effective alternative to oral route with peak effect at 30 minutes; should be the first-choice parenteral route for patients unable to take oral or transdermal opioids 1

• Transdermal (TD): Continuous delivery system worn for up to 72 hours; only for opioid-tolerant patients, not for opioid-naïve individuals 1, 2

• Transmucosal/Buccal: Rapid-onset formulations (fentanyl lozenges, buccal tablets, buccal soluble films) for breakthrough pain in opioid-tolerant patients only; initiate with lowest dose (200-mcg lozenge or 100-mcg buccal tablet) 1

• Rectal: Alternative route when oral administration is not feasible 1

• Intrathecal: Specialized route requiring referral to pain specialists 1

• Nasal: Alternative route with onset times of 12-22 minutes and peak effect at 24-60 minutes; studied for fentanyl, alfentanil, sufentanil, butorphanol, oxycodone, and buprenorphine 3

Routes to Avoid

• Intramuscular injections: Have wider fluctuations in absorption and more rapid fall-off of action compared to oral route 1

• Inhalation (snorting, smoking, vaping): Associated with abuse patterns, particularly in younger males with longer duration of opioid exposure 4

• Injection (IV abuse): Commonly associated with transmission of infectious diseases like hepatitis and HIV 5

Common Opioid Names and Formulations

Pure Opioid Agonists for Severe Pain

• Morphine: Available in immediate-release and extended-release oral formulations, IV, SC, and rectal routes 1, 6

• Fentanyl: Available as transdermal patches (25-100 mcg/h), transmucosal lozenges (200-1600 mcg), buccal tablets (100-800 mcg), buccal soluble films, IV, and SC formulations 1, 2, 3

• Hydromorphone: Available in oral and parenteral formulations 1

• Oxycodone: Available in immediate-release and extended-release oral formulations, IV route 1, 7, 3

• Methadone: Long half-life (8 to >120 hours) requiring specialist consultation due to complex pharmacokinetics and high potency 1, 8

• Buprenorphine: Partial agonist available in sublingual, transdermal, and long-acting injectable formulations; used for opioid substitution treatment 1, 8, 3

• Levomethadone: Used in opioid substitution treatment 8

• Slow-release oral morphine (SROM): Used in opioid substitution treatment 8

• Diamorphine (heroin): Used in heroin-assisted treatment programs for therapy-refractory opioid dependence 8

Pure Opioid Agonists for Moderate Pain

• Hydrocodone: Typically combined with acetaminophen in oral formulations 5

• Codeine: Often combined with acetaminophen or other non-opioids 1

Opioids for Nasal Administration

• Alfentanil: Bioavailability 46-71%, time to maximum concentration 5-50 minutes 3

• Sufentanil: Studied for nasal administration with similar pharmacokinetic profile 3

• Butorphanol: Mixed agonist-antagonist available for nasal use 3

• Pethidine (Meperidine): Studied for postoperative pain via nasal route, though contraindicated for chronic pain due to neurotoxic metabolites 1, 3

Agents NOT Recommended

• Mixed agonist-antagonists (butorphanol, pentazocine, nalbuphine): Should not be used in combination with pure opioid agonists as they can precipitate withdrawal in opioid-dependent patients 1, 9

• Meperidine: Contraindicated for chronic pain due to accumulation of renally cleared metabolites causing neurotoxicity (seizures) or cardiac arrhythmias 1

• Propoxyphene: Risks far outweigh benefits; inhibits CYP2D6 and should be avoided, especially in patients on tamoxifen 1

Special Considerations for Opioid-Dependent Patients

• Opioid substitution treatment (OST): Recommended options include methadone, buprenorphine, slow-release oral morphine, and levomethadone 8

• Heroin-assisted treatment: Cost-effective alternative using diamorphine for individuals not responding to standard opioid agonists, increasing retention and reducing illicit opioid use 8

• Long-acting buprenorphine formulations: Offer additional benefits in improving treatment adherence 8

• Avoid abrupt discontinuation: Rapid tapering can lead to serious withdrawal symptoms, uncontrolled pain, suicide attempts, and drug-seeking behavior 5, 6

Common Pitfalls to Avoid

• Never use placebos in pain management—this is unethical in clinical practice 1

• Do not initiate transdermal fentanyl in opioid-naïve patients—this is contraindicated and can cause fatal respiratory depression 2

• Avoid converting from fentanyl transdermal to other opioids using standard conversion tables, as this will overestimate the new opioid dose and may result in fatal overdose 2

• Do not combine mixed agonist-antagonists with pure opioid agonists in opioid-dependent patients, as this precipitates abstinence syndrome 1, 9

• Intramuscular injections should be avoided due to unpredictable absorption patterns 1