Hydrocodone

Introduction Overview

Generic Name

hydrocodone

Brand Name

Hysingla ER, Zohydro ER

Dosage Form

Extended-release capsules, extended-release tablets

Drug Class

Antitussives, Opioids (narcotic analgesics)

Pharmacokinetics

Absorption:
Hydrocodone is well absorbed orally with a bioavailability that ranges approximately from 25% to 35%, due to first-pass hepatic metabolism. Following oral administration, hydrocodone peak plasma concentrations occur roughly between 1.3 to 1.8 hours for immediate-release formulations, whereas extended-release formulations such as Hysingla ER and Zohydro ER exhibit prolonged absorption with sustained plasma levels over 12 to 24 hours, supporting their use for around-the-clock pain control. Factors such as gastrointestinal pH, motility, and concurrent food intake can influence hydrocodone absorption rates. Clinical monitoring is essential to ensure adequate analgesic effects while avoiding toxicity during variable absorption conditions.

Distribution:
Hydrocodone is widely distributed throughout the body tissues with an apparent volume of distribution approximately 3.3 to 4 L/kg. It crosses the blood-brain barrier efficiently, accounting for its potent central nervous system effects, including analgesia, euphoria, and respiratory depression. Hydrocodone is approximately 20-25% bound to plasma proteins such as albumin, which is relatively low compared to other opioids, facilitating a higher free fraction in circulation. The distribution is influenced by patient factors like age, body composition, and coexisting diseases. It also crosses the placenta and is present in breast milk, necessitating caution during pregnancy and lactation.

Metabolism:
Hydrocodone undergoes extensive hepatic metabolism primarily via the cytochrome P450 enzyme system, particularly CYP3A4 and CYP2D6 isoenzymes. CYP3A4 predominantly metabolizes hydrocodone to norhydrocodone, a metabolite with minimal opioid activity. CYP2D6 converts hydrocodone to hydromorphone, a more potent active metabolite contributing to analgesic effects. Genetic polymorphisms in CYP2D6 can significantly affect hydrocodone metabolism, leading to variability in drug efficacy and toxicity. Concomitant use of CYP3A4 or CYP2D6 inhibitors or inducers may alter hydrocodone plasma levels, requiring dose adjustments. First-pass metabolism limits oral bioavailability, making pharmacokinetics sensitive to hepatic function.

Elimination:
Hydrocodone and its metabolites are primarily eliminated by renal excretion, with approximately 90% excreted in urine, both as unchanged drug and metabolites. The elimination half-life of immediate-release hydrocodone is approximately 3.8 to 6 hours, while extended-release formulations maintain therapeutic levels with longer dosing intervals (12 to 24 hours). Impaired renal function can lead to accumulation of active metabolites, increasing risk of toxicity. Hydrocodone’s clearance can be significantly reduced in patients with hepatic impairment due to compromised metabolism. Biliary excretion is minimal. Monitoring renal and hepatic function is important for dose individualization and toxicity prevention.

Dosage Forms

Available Dosage Forms:
- Extended-release capsules (Zohydro ER): 10 mg, 20 mg, 30 mg, 40 mg, 50 mg, and 60 mg
- Extended-release tablets (Hysingla ER): 20 mg, 30 mg, 40 mg, 50 mg, 60 mg, 70 mg, 80 mg, 90 mg, 100 mg

Dosages for Adults and Adolescents:
- For chronic severe pain in opioid non-tolerant patients:
- Zohydro ER capsules: Initial dose 10 mg orally every 12 hours
- Hysingla ER tablets: Initial dose 20 mg orally every 24 hours
- Dose titration should be individualized based on patient response and tolerance.
- Higher initial doses in non-opioid tolerant patients may cause fatal respiratory depression; close monitoring during the first 24-72 hours is mandatory.
- Opioid-tolerant patients, defined as receiving specific opioid doses for at least 1 week, may require higher initial doses.

Specific Patient Populations:
- Caution is advised in elderly, debilitated patients, and those with respiratory disorders due to increased risk of respiratory depression.
- Patients with hepatic or renal impairment require dose adjustments or close monitoring because of altered metabolism and elimination.
- Use in pregnancy requires careful risk-benefit assessment; exposure in utero can cause neonatal opioid withdrawal syndrome.
- Breastfeeding mothers should consult healthcare providers as hydrocodone passes into breast milk and may cause sedation or respiratory depression in infants.
- Not recommended for pediatric patients younger than 18 years for extended-release formulations.

Clinical Guidelines:
- Extended-release hydrocodone is indicated for around-the-clock management of severe pain unresponsive to non-opioid analgesics.
- Not for use on an as-needed basis or for mild pain.
- Tablets or capsules must be swallowed whole; crushing, breaking, or opening to avoid rapid release, which can be fatal.
- Dose adjustments should consider opioid tolerance, pain severity, and individual response.

Mechanism Of Action

Hydrocodone is a semi-synthetic opioid analgesic that primarily acts as an agonist at the mu-opioid receptors (MOR) located in the central nervous system. Binding to these G-protein coupled receptors inhibits adenylate cyclase activity, decreasing intracellular cAMP levels, which leads to reduced neuronal excitability and neurotransmitter release. This action decreases transmission of nociceptive signals and produces analgesia.

At the cellular level, hydrocodone binding to MOR induces opening of potassium channels and closing of voltage-gated calcium channels, resulting in neuronal hyperpolarization and decreased release of excitatory neurotransmitters such as substance P, glutamate, and calcitonin gene-related peptide (CGRP) in the dorsal horn of the spinal cord. This diminishes the propagation of pain signals ascending to the brain.

Hydrocodone also affects the brain stem respiratory centers, which can suppress the cough reflex and respiratory drive, accounting for its antitussive properties but also risks of respiratory depression. Its agonism at mu-opioid receptors in limbic brain regions produces euphoria and sedation, contributing to its potential for addiction and abuse.

Compared to other opioids like oxycodone, hydrocodone has slightly lower analgesic potency but similar pharmacodynamic profiles. Research indicates that genetic variability in CYP2D6 metabolism affects conversion to hydromorphone, contributing to interpatient variability in efficacy and adverse effects. Clinical trials have demonstrated hydrocodone’s efficacy in managing moderate to severe pain when used appropriately and underscore the importance of risk mitigation strategies to reduce misuse and overdose.

Pharmacological Actions

Binds as a potent agonist to central nervous system mu-opioid receptors producing analgesia.
Suppresses cough reflex via action on brainstem cough centers (antitussive effect).
Reduces transmission of pain signals by decreasing neurotransmitter release in spinal cord dorsal horn.
Produces sedation and euphoria by action on limbic system opioid receptors.
Modulates respiratory centers leading to respiratory depression at high doses.
Causes gastrointestinal effects such as decreased motility contributing to constipation.
Induces miosis (pinpoint pupils) via parasympathetic stimulation.
Can cause hormonal changes including decreased hypothalamic-pituitary-adrenal axis activity.
Activates potassium channels and inhibits calcium channels to reduce neuronal excitability.
Potentially affects serotonin pathways influencing mood and autonomic functions.
Has abuse potential due to reinforcing dopaminergic effects via opioid receptor interaction.
Exhibits dependency and tolerance following long-term administration.
Inhibits ascending pain pathways leading to altered pain perception.
Exerts antidiarrheal effects through opioid receptors in gastrointestinal tract.

Therapeutic Or Clinical Uses

Management of moderate to severe chronic pain requiring continuous opioid analgesia.
Around-the-clock treatment of severe pain unresponsive to non-opioid analgesics.
Use as an antitussive agent to suppress persistent cough symptoms in limited situations.
Postoperative pain control in selected patients when prescribed.
Adjunct therapy in cancer-related pain management.
Treatment option for patients with opioid tolerance requiring stronger analgesics.
Alternative analgesic in patients allergic or intolerant to other opioids.
Used in palliative care settings to improve quality of life by pain relief.
Management of neuropathic pain in specific clinical scenarios.
Off-label use in severe refractory cough under careful supervision.
Control of pain associated with musculoskeletal disorders.
Pain relief following traumatic injuries when other analgesics are inadequate.
Part of multimodal analgesia regimens for enhanced pain control.
Moderate to severe pain relief in patients with chronic conditions such as osteoarthritis.

Side Or Adverse Effects

Respiratory depression ranging from mild hypoventilation to fatal apnea.
Constipation due to decreased gastrointestinal motility.
Nausea and vomiting frequently observed especially at treatment initiation.
Dizziness, sedation, and drowsiness affecting alertness and coordination.
Headache and generalized fatigue or weakness.
Pruritus and skin rash including rare allergic-type reactions.
Miosis (pinpoint pupils) characteristic of opioid use.
Potential for development of dependence, tolerance, and withdrawal symptoms.
Hypotension and bradycardia in sensitive individuals.
Confusion, mood changes including euphoria or dysphoria.
Urinary retention due to smooth muscle relaxation effects.
Serotonin syndrome risk if combined with serotonergic agents.
Hypogonadism and impaired fertility with prolonged use.
Respiratory complications more severe in elderly or debilitated patients.
Potential for opioid-induced hyperalgesia with long-term therapy.

Precautions

Monitor closely for signs of respiratory depression especially during initiation or dose escalation.
Assess patient history for opioid tolerance before initiating therapy to avoid overdose risks.
Use cautiously in patients with respiratory disorders such as asthma or sleep apnea.
Avoid abrupt discontinuation; taper dose gradually to prevent withdrawal symptoms.
Screen for history of substance abuse or addiction prior to prescribing.
Evaluate hepatic and renal function to adjust dosing accordingly.
Avoid coadministration with CNS depressants including benzodiazepines unless carefully monitored.
Pregnant women should use only if clearly needed; monitor neonates for withdrawal symptoms.
Use caution when prescribing to elderly or debilitated patients due to increased sensitivity.
Assess for potential drug interactions that may alter hydrocodone metabolism or effect.
Advise patients against driving or operating heavy machinery until effects are known.
Store medication securely to prevent misuse or accidental ingestion, particularly by children.
Educate patients about the risk of addiction, overdose, and safe disposal of unused medication.
Evaluate for serotonin syndrome symptoms when used concomitantly with serotonergic drugs.
Recommend naloxone availability for patients at risk of opioid overdose.

Warnings

Hydrocodone can cause life-threatening respiratory depression; avoid doses higher than prescribed.
Do not crush, break, or open extended-release formulations to prevent rapid release and fatal overdose.
Potential for addiction, abuse, and misuse exists even at prescribed doses.
Sharing medication with others is illegal and dangerous; keep out of reach of children and unauthorized persons.
Concomitant use with alcohol or other CNS depressants can result in fatal respiratory depression.
Use during pregnancy may cause neonatal opioid withdrawal syndrome which can be life-threatening.
Not recommended for use as needed for pain; indicated only for continuous around-the-clock use.
Older adults and patients with chronic lung conditions are at increased risk for respiratory complications.
Overdose symptoms include severe drowsiness, pinpoint pupils, and slowed or stopped breathing; seek emergency care.
Sudden discontinuation after long-term use can precipitate severe withdrawal symptoms.
Patients should be closely monitored for increased opioid use or signs of misuse.
Respiratory depression risk is highest in the first 24 to 72 hours of therapy initiation or dose increase.
Naloxone should be prescribed and accessible for reversal of opioid overdose.
Avoid in patients with severe asthma or gastrointestinal obstruction.
Serotonin syndrome is a risk when combined with serotonergic agents; immediate medical attention needed.

Contraindication

Known hypersensitivity or allergy to hydrocodone or any component of the formulation.
Severe respiratory depression or acute bronchial asthma in unmonitored settings.
Paralytic ileus or gastrointestinal obstruction including bowel obstruction.
Significant respiratory compromise, including sleep apnea in non-hospitalized settings.
Hypersensitivity to opioids or history of opioid-induced anaphylaxis.
Patients who have or are suspected of having severe central nervous system depression.
Known or suspected gastrointestinal obstruction due to risk of worsening condition.
Patients who have been taking monoamine oxidase inhibitors (MAOIs) within the last 14 days.
Use contraindicated in all pediatric patients under 18 years for extended-release formulations.
Active or untreated head injury or increased intracranial pressure where respiratory depression can worsen outcome.
Severe hepatic impairment due to risk of accumulation and toxicity.
Patients with acute alcoholism or delirium tremens due to potentiation of CNS depression.
Hypersensitivity to morphine derivatives predisposing to cross-reactivity with hydrocodone.
Concomitant use with other CNS depressants without appropriate monitoring.
Patients with known or suspected intoxication with alcohol, hypnotics, narcotics, or psychotropic drugs.

Drug Interactions

Concomitant use with benzodiazepines or other sedatives increases risk of respiratory depression and sedation.
CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, clarithromycin) can elevate hydrocodone plasma levels, increasing toxicity risk.
CYP3A4 inducers (e.g., rifampin, carbamazepine) can decrease hydrocodone efficacy by increasing metabolism.
CYP2D6 inhibitors (e.g., fluoxetine, paroxetine) may decrease conversion to hydromorphone, reducing analgesic effect.
Use with other opioids or opioid-containing products enhances CNS depressant effects and risk of overdose.
Co-administration with alcohol can cause potentiation of CNS and respiratory depression, potentially fatal.
Drugs affecting serotonin levels (e.g., SSRIs, MAOIs, triptans) may increase risk of serotonin syndrome.
Concomitant use with muscle relaxants or anticonvulsants can enhance sedation and respiratory depression.
Diuretics and antihypertensive drugs may have altered effects due to hydrocodone-induced vasodilation or volume changes.
Anticholinergic drugs may exacerbate opioid-induced urinary retention and constipation.
Drugs that cause CNS depression (e.g., antipsychotics, sedative-hypnotics) increase risk of profound sedation.
Certain antibiotics and antifungal agents can interfere with hydrocodone metabolism altering plasma levels.
Interaction with seizure medications may alter seizure threshold or drug levels.
HIV and hepatitis C treatments metabolized via CYP450 may modify hydrocodone clearance.
Cold and allergy medications containing sedating antihistamines may potentiate hydrocodone side effects.

Preparations Of The Drug

Zohydro ER extended-release capsules available in 10 mg, 20 mg, 30 mg, 40 mg, 50 mg, and 60 mg strengths.
Hysingla ER extended-release tablets available in 20 mg through 100 mg increments.
Immediate-release hydrocodone formulations combined with acetaminophen or ibuprofen (not highlighted in this monograph but commonly used commercially).
Extended-release formulations designed for once or twice daily dosing in chronic pain management.
Oral tablets and capsules must be swallowed whole; designed with abuse-deterrent properties in some formulations.
Commercially available labeled for prescription use with detailed dosing and safety instructions.
Available in unit-dose packaging for outpatient prescriptions.
Manufactured adhering to FDA guidelines for controlled substances with risk evaluation and mitigation strategies (REMS).
Formulations are designed for oral administration with no parenteral forms for hydrocodone alone commercially approved.
Storage instructions recommend room temperature away from moisture and heat.
Packaging includes patient information emphasizing risks of misuse, addiction, and proper disposal.
May be available under other brand names such as Vantrela ER in some markets.
All preparations are scheduled controlled substances due to abuse potential.
Preparations vary in opioid content requiring careful prescription and dispensing practices.
Co-formulations (e.g., hydrocodone with acetaminophen) are distinct dosage forms and require separate consideration.