What Is Oxycodone Hydrochloride (Oxopane)? FDA Approval, Authorization in Türkiye, and Reimbursement

• FDA Approval: Yes, Initial Approval: 5 December 1950 (long-acting formulation: 1995)
• Brand Name: Oxopane
• Active Ingredient: Oxycodone Hydrochloride
• Administration: Oral tablets (immediate-release, extended-release), oral capsules, oral solution, oral concentrate, rectal suppositories (in limited regions)
• Class: Opioid analgesic (narcotic painkiller)
• Category: Severe chronic pain, Cancer-related pain, Postoperative pain, severe trauma-related pain
• Original Manufacturer: Purdue Pharma (OxyContin). Other generic manufacturers: Mallinckrodt, Hikma, Teva, etc.
• Availability in Türkiye: Under SGK coverage, only as a prescription-controlled medicine
• Approved Cancers (Indication): Not approved for a specific cancer type, but approved by the FDA and EMA to control severe chronic cancer-related pain.

What Is Oxycodone Hydrochloride? How Does It Work?

Oxycodone hydrochloride is a semisynthetic opioid analgesic. Derived from natural opioids such as morphine, it treats severe pain. It is used to control both acute and chronic pain, particularly severe cancer-related or postoperative pain. It is an FDA-approved narcotic analgesic acting on the central nervous system.

What Is Its Mechanism of Action?

Oxycodone acts primarily as a μ-opioid (mu) receptor agonist and binds κ (kappa) and δ (delta) opioid receptors to a lesser extent.

Receptor Interaction: Oxycodone binds with high affinity to μ-opioid receptors in the central nervous and gastrointestinal systems.

G-Protein-Coupled Receptor Activation:These receptors act through inhibitory G proteins (Gi/o). Following receptor activation:

• Adenylate cyclase activity is inhibited.
• cAMP (cyclic adenosine monophosphate) levels decrease.
• K⁺ channels open and the neuron hyperpolarizes.
• Ca²⁺ channels close, reducing neurotransmitter release (glutamate, substance P).

Suppression of Neural Transmission: Transmission of pain-related afferent signals is suppressed at the dorsal horn and brainstem. Thus:

• Pain perception
• and generation of the sensory response are significantly inhibited.

FDA (US Food and Drug Administration) Approval History

• 20 June 2011: Pfizer and Acura announced FDA approval for Oxecta (Oxycodone HCl, USP) CII.
• 20 December 2010: King Pharmaceuticals and Acura Pharmaceuticals announced a New Drug Application (NDA) for Acurox tablets.
• 4 May 2010: King Pharmaceuticals and Acura Pharmaceuticals announced plans to submit a New Drug Application for niacin-free Acurox tablets.
• 23 April 2010: Acura Pharmaceuticals and King Pharmaceuticals shared an update on the FDA Advisory Committee Meeting concerning Acurox.
• 3 September 2009: Acura Pharmaceuticals and King Pharmaceuticals provided an update on the Acurox New Drug Application (NDA).
• 2 July 2009: Acura and King reported receiving an FDA Complete Response Letter for Acurox.
• 3 March 2009: The New Drug Application for Acurox tablets was accepted for FDA priority review.
• 2 January 2009: A New Drug Application (NDA) was submitted for Acurox tablets.

Authorization in Türkiye

Authorized in Türkiye and reimbursed by SGK.

Price: Oxopane 5 mg, 56 capsules: 143.09 TL; Oxopane 10 mg, 56 capsules: 247.90 TL; Oxopane 20 mg, 56 capsules: 493.73 TL.

Resistance Mechanisms

Opioid Receptor Desensitization

• Persistent stimulation of μ-opioid receptors (MORs) causes desensitization through phosphorylation.
• Desensitized receptors become uncoupled from G-protein signaling and lose activity.

Receptor Downregulation

• Chronic oxycodone use causes receptor internalization and a reduction in receptor numbers.
• The same drug dose then produces a smaller effect (pharmacodynamic tolerance).

Adenylate Cyclase Supersensitization

• After prolonged MOR activation, adenylate cyclase activity increases as compensation.
• The resulting rise in cAMP may reactivate pain transmission.

Neuronal Plasticity and NMDA Activation

• Chronic opioid use may cause excessive glutamate/NMDA receptor activation in the central nervous system.
• This contributes to opioid-induced hyperalgesia (increased pain sensitivity) and tolerance.

Neuroinflammation and Glial Activation

• Microglia and astrocytes may become activated in response to opioid stimulation.
• These cells release cytokines (IL-1β, TNF-α, IL-6) and proinflammatory mediators.
• This triggers both tolerance and recurrence of pain.

Increased Efflux Transport Proteins (Multidrug Resistance Proteins – MDR)

• Expression of transport proteins, particularly P-glycoprotein (P-gp), may increase.
• Drugs such as oxycodone cross the blood–brain barrier less effectively, reducing central effects.

Absorption

• Oral bioavailability: Approximately 60–87% (high despite first-pass metabolism)
• Onset: Oral formulations: 10–30 minutes
• Time to peak plasma level: Immediate-release: 1–1.5 hours; Extended-release: 3–4.5 hours
• Food effect: Does not affect absorption, although the absorption rate of the extended-release formulation may change slightly.

Distribution

• Volume of distribution (Vd): 2.6 L/kg (mean)
• Plasma protein binding: 38–45% (primarily albumin)
• Can cross the blood–brain barrier, explaining its central effects (analgesia, euphoria, depression).

Metabolism

• Metabolized in the liver (phase I metabolism)
• Main metabolic pathways: CYP3A4; Noroxycodone (inactive or minimally active) CYP2D6; Oxymorphone (more potent active metabolite)
• Phase II conjugation: Oxycodone and its metabolites undergo glucuronidation, becoming water-soluble metabolites.
• There is substantial potential for clinical interactions with CYP3A4 and CYP2D6 variations or inhibitory/inducing drugs.

Excretion

• Half-life (t1/2): Immediate-release: 3–4 hours; Extended-release: 10–12 hours
• Route of elimination: 70% via the kidneys (urine)
• Free oxycodone: 8%
• Conjugated metabolites: 60+%, 6–10% via feces
• Elimination may vary according to creatinine clearance.
• Use cautiously in patients with renal impairment.

Dose Range

Immediate-Release Oxycodone (IR)

• Opioid-naive adults: 5–10 mg orally every 4–6 hours.
• Opioid-tolerant adults: 10–30 mg orally every 4–6 hours.
• Older adults (>65 years): 2.5–5 mg orally every 6 hours; titrate slowly.

Extended-Release Oxycodone (ER / OxyContin):

• Opioid-naive adults: Generally not recommended; if started, 10 mg every 12 hours.
• Opioid-tolerant adults: Individualized according to the previous opioid dose.

Parenteral (IV/Subcutaneous/IM) Formulations

• IV: 1–2 mg by slow IV push every 4 hours.
• SC/IM: 5 mg every 4–6 hours.

Extended-release tablets must not be crushed, chewed, or split and must be swallowed whole.

Crushing or breaking allows the entire dose to be absorbed rapidly, creating overdose and respiratory depression risks.

Generally may be taken with or without food.

However, taking it with food may be advised for people with a sensitive stomach.

Because it can cause sedation, dizziness, and reduced attention, use caution when driving or operating machinery.

Do not stop oxycodone abruptly.

After long-term use, the dose should be tapered gradually to prevent withdrawal syndrome.

Seek urgent medical attention for side effects such as dizziness, nausea, excessive sleepiness, or shortness of breath.

Treatment duration, dosing intervals, and discontinuation should be planned under medical supervision.

Drug Interactions

CYP3A4 Inhibitors

These drugs slow oxycodone metabolism, increasing plasma levels and the risks of toxicity and respiratory depression.

• Azole antifungals (ketoconazole, itraconazole)
• Macrolide antibiotics (clarithromycin, erythromycin)
• HIV protease inhibitors (ritonavir)
• Verapamil, diltiazem
• Grapefruit juice

CYP3A4 Inducers

Metabolism accelerates and efficacy falls, potentially causing inadequate analgesia.

• Rifampicin
• Carbamazepine
• Phenytoin
• St. John's Wort

CYP2D6 Inhibitors

Formation of oxycodone's active metabolite oxymorphone decreases, potentially reducing analgesia.

• Paroxetine, fluoxetine
• Bupropion
• Quinidine

Other Central Nervous System Depressants

Concurrent use increases the risks of sedation, respiratory depression, and coma.

• Benzodiazepines (diazepam, lorazepam)
• Barbiturates
• Alcohol
• Antihistamines (sedating agents such as diphenhydramine)
• Muscle relaxants
• Antipsychotics

MAO Inhibitors (concurrent use or use within the past 14 days)

• Increased risk of hypotension, respiratory depression, serotonin syndrome, or coma.
• The combination is not recommended.

Interactions With Diuretics and Antihypertensives

• By suppressing the baroreceptor response, oxycodone may enhance the effects of blood pressure-lowering drugs.
• It also masks diuretic effects (for example, pain suppression may reduce thirst).

Special Situations Requiring Caution

Risk of Respiratory Depression

Oxycodone suppresses the respiratory center in a dose-dependent manner.

Close monitoring is particularly needed for:

• Opioid-naive patients
• Older adults
• People with pulmonary disease (COPD, sleep apnea)
• Those taking concomitant CNS depressants (benzodiazepines, alcohol)

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Dependence and Abuse Potential

• Oxycodone can cause physical and psychological dependence.
• Tolerance may develop with high-dose or long-term use.
• Prescribe cautiously in people with a history of addiction.
• Pregnancy and Breastfeeding
• Pregnancy Category C (US FDA): May harm the fetus.
• Long-term use may cause neonatal withdrawal syndrome.
• Breastfeeding: Passes into milk, creating a risk of respiratory depression and sedation in the breastfed infant.

Hepatic Impairment

• Oxycodone is metabolized in the liver (CYP3A4 and CYP2D6).
• Hepatic impairment reduces drug clearance, increasing accumulation and toxicity risks.
• Start with low doses and titrate slowly.

Renal Impairment

• Oxycodone and its metabolites are excreted by the kidneys.
• Its effect may be prolonged in uremic patients, creating a risk of accumulation.
• Extend dosing intervals and monitor carefully.

Older Patients (≥65 years)

• Drug clearance may decrease and sensitivity increase with age.
• Reduce the starting dose and titrate cautiously.

Gastrointestinal Conditions

• Oxycodone slows motility, and constipation is common.
• Do not use in patients with paralytic ileus, obstruction, or bile duct disease.
• Concurrent use with anticholinergics increases ileus risk.

Head Trauma and Increased Intracranial Pressure

• Oxycodone can raise intracranial pressure by causing carbon dioxide retention.
• Use is inadvisable in patients with elevated intracranial pressure.

Hypotension Risk

• Oxycodone may cause orthostatic hypotension through histamine release and peripheral vasodilation.
• Use particular caution in hypovolemic patients.

Use With Alcohol

• When oxycodone, particularly the extended-release formulation, is taken with alcohol:
• The entire drug dose may be released at once (dose dumping)
• Severe respiratory depression and a risk of death may result.

Side Effects

• Constipation: 23–36%
• Nausea: 21–34%
• Dizziness: 13–27%
• Vomiting: 12–25%
• Headache: 10–18%
• Sedation / Somnolence: 15–24%
• Dry mouth: 8–15%
• Itching (pruritus): 7–13%
• Fatigue / Weakness: 10–16%
• Dysphoria / Euphoria / Mood changes: 5–12%
• Reduced appetite: 6–10%
• Sweating (hyperhidrosis): 5–10%
• Confusion: 4–9%
• Insomnia (difficulty sleeping): 5–9%
• Respiratory depression: 1–5%
• Orthostatic hypotension: 1–4%
• Urinary retention (inability to urinate): 1–4%
• Miosis (constricted pupils): 2–4%
• Clouded consciousness / Lightheadedness: 2–5%
• Drug tolerance / Dependence: Unknown (increases with long-term use)