Pharmacology:

The analgesic ingredient, oxycodone, is a semi-synthetic narcotic with multiple actions qualitatively similar to those of morphine; the most prominent of these involves the central nervous system and organs composed of smooth muscle.

Oxycodone, as the hydrochloride salt, is a pure agonist opioid whose principal therapeutic action is analgesia and has been in clinical use since 1917. Like all pure opioid agonists, there is no ceiling effect to analgesia, such as is seen with partial agonists or non-opioid analgesics. Based upon a single-dose, relative-potency study conducted in humans with cancer pain, 10 to 15 mg of oxycodone given intramuscularly produced an analgesic effect similar to 10 mg of morphine given intramuscularly. Both drugs have a 3 to 4 hour duration of action. Oxycodone retains approximately one half of its analgesic activity when administered orally.

Effects on Central Nervous System: The precise mechanism of the analgesic action is unknown. However, specific CNS opioid receptors for endogenous compounds with opioid-like activity have been identified throughout the brain and spinal cord and play a role in the analgesic effects of this drug. A significant feature of opioid-induced analgesia is that it occurs without loss of consciousness. The relief of pain by morphine-like opioids is relatively selective, in that other sensory modalities, (e.g., touch, vibrations, vision, hearing, etc.) are not obtunded.

Oxycodone produces respiratory depression by direct action on brain stem respiratory centers. The respiratory depression involves both a reduction in the responsiveness of the brain stem respiratory centers to increases in carbon dioxide tension and to electrical stimulation.

Oxycodone depresses the cough reflex by direct effect on the cough center in the medulla. Antitussive effects may occur with doses lower than those usually required for analgesia. Oxycodone causes miosis, even in total darkness. Pinpoint pupils are a sign of opioid overdose but are not pathognomonic (e.g., pontine lesions of hemorrhagic or ischemic origins may produce similar findings). Marked mydriasis rather than miosis may be seen due to hypoxia in overdose situations.

Effects on Gastrointestinal Tract And Other Smooth Muscle: Oxycodone, like other opioid analgesics, produces some degree of nausea and vomiting which is caused by direct stimulation of the chemoreceptor trigger zone (CTZ) located in the medulla. The frequency and severity of emesis gradually diminishes with time.

Oxycodone may cause a decrease in the secretion of hydrochloric acid in the stomach that reduces motility while increasing the tone of the antrum, stomach, and duodenum. Digestion of food in the small intestine is delayed and propulsive contractions are decreased. Propulsive peristaltic waves in the colon are decreased, while tone may be increased to the point of spasm resulting in constipation. Other opioid-induced effects may include a reduction in biliary and pancreatic secretions, spasm of sphincter of Oddi, and transient elevations in serum amylase.

Effects on Cardiovascular System: Oxycodone, in therapeutic doses, produces peripheral vasodilatation (arteriolar and venous), decreased peripheral resistance, and inhibits baroreceptor reflexes. Manifestations of histamine release and/or peripheral vasodilatation may include pruritus, flushing, red eyes, sweating, and/or orthostatic hypotension.

Caution should be used in hypovolemic patients, such as those suffering acute myocardial infarction, because oxycodone may cause or further aggravate their hypotension. Caution should also be used in patients with cor pulmonale who have received therapeutic doses of opioids.

Pharmacodynamics:

The relationship between the plasma level of oxycodone and the analgesic response will depend on the patient's age, state of health, medical condition and extent of previous opioid treatment.

The minimum effective plasma concentration of oxycodone to achieve analgesia will vary widely among patients, especially among patients who have been previously treated with potent agonist opioids. Thus, patients need to be treated with individualized titration of dosage to the desired effect. The minimum effective analgesic concentration of oxycodone for any individual patient may increase with repeated dosing due to an increase in pain and/or development of tolerance.

Pharmacokinetics:

The activity of oxycodone hydrochloride tablets is primarily due to the parent drug oxycodone. Oxycodone hydrochloride tablets are designed to provide immediate release of oxycodone.

  Absorption: About 60% to 87% of an oral dose of oxycodone reaches the systemic circulation in comparison to a parenteral dose. This high oral bioavailability (compared to other oral opioids) is due to lower pre-systemic and/or first-pass metabolism of oxycodone. The relative oral bioavailability of oxycodone hydrochloride 15 mg and 30 mg tablets, compared to the 5 mg oxycodone hydrochloride tablets, is 96% and 101% respectively. Oxycodone hydrochloride 15 mg tablets and 30 mg tablets are bioequivalent to the 5 mg oxycodone hydrochloride tablets (see Table 1 for pharmacokinetic parameters). Dose proportionality of oxycodone has been established using the oxycodone hydrochloride 5 mg tablets at doses of 5 mg, 15 mg (three 5 mg tablets) and 30 mg (six 5 mg tablets) based on extent of absorption (AUC) (see Figure 1). It takes approximately 18 to 24 hours to reach steady-state plasma concentrations of oxycodone with oxycodone hydrochloride tablets.

Figure 1 - Oxycodone Hydrochloride Tablets Dose-Proportionality Study 5 mg, 15 mg and 30 mg (single-dose)

Food Effect: A single-dose food effect study was conducted in normal volunteers using the 5 mg/5 mL solution. The concurrent intake of a high fat meal was shown to enhance the extent (27% increase in AUC), but not the rate of oxycodone absorption from the oral solution (see Table 1). In addition, food caused a delay in Tmax (1.25 to 2.54 hour). Similar effects of food are expected with the 15 mg and 30 mg tablets.

Distribution: Following intravenous administration, the volume of distribution (Vss) for oxycodone was 2.6 L/kg. Plasma protein binding of oxycodone at 37°C and a pH of 7.4 was about 45%. Oxycodone has been found in breast milk (see PRECAUTIONS-Nursing Mothers).

Metabolism: Oxycodone hydrochloride is extensively metabolized to noroxycodone, oxymorphone, and their glucuronides. The major circulating metabolite is noroxycodone with an AUC ratio of 0.6 relative to that of oxycodone. Oxymorphone is present in the plasma only in low concentrations. The analgesic activity profile of other metabolites is not known at present.

The formation of oxymorphone, but not noroxycodone, is mediated by CYP2D6 and as such its formation can, in theory, be affected by other drugs (see PRECAUTIONS-Drug Interactions ).

Elimination: Oxycodone and its metabolites are excreted primarily via the kidney. The amounts measured in the urine have been reported as follows: free oxycodone up to 19%; conjugated oxycodone up to 50%; free oxymorphone 0%; conjugated oxymorphone ≤ 14%; both free and conjugated noroxycodone have been found in the urine but not quantified. The total plasma clearance was 0.8 L/min for adults. Apparent elimination half-life of oxycodone following the administration of oxycodone hydrochloride tablets was 3.5 to 4 hours.

Special Populations:

Geriatric: Population pharmacokinetic studies conducted with oxycodone hydrochloride tablets, indicated that the plasma concentrations of oxycodone did not appear to be increased in patients over the age of 65.

Gender: Population pharmacokinetic analyses performed in the clinical study support the lack of gender effect on the pharmacokinetics of oxycodone from oxycodone hydrochloride tablets.

Race: Population pharmacokinetic analyses support the lack of race effect on oxycodone pharmacokinetics after administration of oxycodone hydrochloride tablets, but these data should be interpreted conservatively, since the majority of patients enrolled into the studies were Caucasians (94%).

Renal Insufficiency: In a clinical trial supporting the development of oxycodone hydrochloride tablets, too few patients with decreased renal function were evaluated to study these potential differences. In previous studies, patients with renal impairment (defined as a creatinine clearance < 60 mL/min) had concentrations of oxycodone in the plasma that were higher than in subjects with normal renal function. Based on information available on the metabolism and excretion of oxycodone, dose initiation in patients with renal impairment should follow a conservative approach. Dosages should be adjusted according to the clinical situation.

Hepatic Failure: In a clinical trial supporting the development of oxycodone hydrochloride tablets, too few patients with decreased hepatic function were evaluated to study these potential differences. However, since oxycodone is extensively metabolized, its clearance may decrease in hepatic failure patients. Dose initiation in patients with hepatic impairment should follow a conservative approach. Dosages should be adjusted according to the clinical situation.

General

Oxycodone hydrochloride tablets are intended for use in patients who require oral pain therapy with an opioid agonist. As with any opioid analgesic, it is critical to adjust the dosing regimen individually for each patient (seeDOSAGE AND ADMINISTRATION).

Selection of patients for treatment with oxycodone hydrochloride tablets should be governed by the same principles that apply to the use of other potent opioid analgesics. Opioid analgesics given on a fixed-dosage schedule have a narrow therapeutic index in certain patient populations, especially when combined with other drugs, and should be reserved for cases where the benefits of opioid analgesia outweigh the known risks of respiratory depression, altered mental state, and postural hypotension. Physicians should individualize treatment in every case, using nonopioid analgesics, prn opioids and /or combination products, and chronic opioid therapy with drugs such as oxycodone hydrochloride tablets in a progressive plan of pain management such as outlined by the World Health Organization, the Agency for Health Care Policy and Research, and the American Pain Society.

Use of oxycodone hydrochloride tablets is associated with increased potential risks and should be used only with caution in the following conditions: acute alcoholism; adrenocortical insufficiency (e.g., Addison's disease); convulsive disorders; CNS depression or coma; delirium tremens; debilitated patients; kyphoscoliosis associated with respiratory depression; myxedema or hypothyroidism; prostatic hypertrophy or urethral stricture; severe impairment of hepatic, pulmonary or renal function; and toxic psychosis.

The administration of oxycodone hydrochloride tablets, like all opioid analgesics, may obscure the diagnosis or clinical course in patients with acute abdominal conditions. Oxycodone may aggravate convulsions in patients with convulsive disorders, and all opioids may induce or aggravate seizures in some clinical settings.

Tolerance and Physical Dependence:

Physical dependence and tolerance are not unusual during chronic opioid therapy. Significant tolerance should not occur in most patients treated with the lowest doses of oxycodone. It should be expected, however, that a fraction of patients will develop some degree of tolerance and require progressively higher dosages of oxycodone hydrochloride tablets to maintain pain control during chronic treatment. The dosage should be selected according to the patient's individual analgesic response and ability to tolerate side effects. Tolerance to the analgesic effects of opioids is usually paralleled by tolerance to side effects except for constipation.

Physical dependence results in withdrawal symptoms in patients who abruptly discontinue the drug or may be precipitated through the administration of drugs with opioid antagonist activity. If oxycodone hydrochloride tablets is abruptly discontinued in a physically dependent patient, an abstinence syndrome may occur (see DRUG ABUSE AND DEPENDENCE). If signs and symptoms of withdrawal occur, patients should be treated by reinstitution of opioid therapy followed by gradual tapered dose reduction of oxycodone hydrochloride tablets combined with symptomatic support (see Cessation of Therapy:: Cessation of Therapy:).

Use in Pancreatic/Biliary Tract Disease:

Oxycodone hydrochloride tablets may cause spasm of the sphincter of Oddi and should be used with caution in patients with biliary tract disease, including acute pancreatitis. Opioids like oxycodone hydrochloride tablets may cause increases in the serum amylase level.

Information for Patients

If clinically advisable, patients (or their caregivers) receiving oxycodone hydrochloride tablets should be given the following information by the physician, nurse, pharmacist or caregiver:

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Patients should be advised to report episodes of breakthrough pain and adverse experiences occurring during therapy. Individualization of dosage is essential to make optimal use of this medication.

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Patients should be advised not to adjust the dose of oxycodone hydrochloride tablets without consulting the prescribing professional.

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Patients should be advised that oxycodone hydrochloride tablets may impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery).

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Patients should not combine oxycodone hydrochloride tablets with alcohol or other central nervous system depressants (sleep aids, tranquilizers) except by the orders of the prescribing physician, because additive effects may occur.

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Women of childbearing potential who become, or are planning to become pregnant, should be advised to consult their physician regarding the effects of analgesics and other drug use during pregnancy on themselves and their unborn child.

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Patients should be advised that oxycodone hydrochloride tablets are a potential drug of abuse. They should protect it from theft, and it should never be given to anyone other than the individual for whom it was prescribed.

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Patients should be advised that if they have been receiving treatment with oxycodone hydrochloride tablets for more than a few weeks and cessation of therapy is indicated, it may be appropriate to taper the oxycodone hydrochloride tablets dose, rather than abruptly discontinue it, due to the risk of precipitating withdrawal symptoms. Their physician can provide a dose schedule to accomplish a gradual discontinuation of the medication.

Interactions

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term studies have not been performed in animals to evaluate the carcinogenic potential of oxycodone hydrochloride tablets or oxycodone. The possible effects on male or female fertility have not been studied in animals.

Oxycodone hydrochloride was genotoxic in an in vitro mouse lymphoma assay in the presence of metabolic activation. There was no evidence of genotoxic potential in an in vitro bacterial reverse mutation assay (Salmonella typhimurium and Escherichia coli) or in an assay for chromosomal aberrations (in vivo mouse bone marrow micronucleus assay).

Pregnancy

Labor and Delivery

Oxycodone hydrochloride tablets are not recommended for use in women during or immediately prior to labor. Occasionally, opioid analgesics may prolong labor through actions which temporarily reduce the strength, duration and frequency of uterine contractions. Neonates, whose mothers received opioid analgesics during labor, should be observed closely for signs of respiratory depression. A specific narcotic antagonist, naloxone, should be available for reversal of narcotic-induced respiratory depression in the neonate.

Nursing Mothers

Oxycodone has been detected in breast milk. Withdrawal symptoms can occur in breast-feeding infants when maternal administration of an opioid analgesic is stopped. Ordinarily, nursing should not be undertaken while a patient is receiving oxycodone hydrochloride tablets since oxycodone may be excreted in milk.

Pediatric Use

The safety and efficacy of oxycodone in pediatric patients have not been evaluated.

Geriatric Use

Of the total number of subjects in clinical studies of oxycodone hydrochloride tablets, 20.8% (112/538) were 65 and over, while 7.2% (39/538) were 75 and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

Hepatic Impairment:

Since oxycodone is extensively metabolized, its clearance may decrease in hepatic failure patients. Dose initiation in patients with hepatic impairment should follow a conservative approach. Dosages should be adjusted according to the clinical situation.

Renal Impairment:

Published data reported that elimination of oxycodone was impaired in end-stage renal failure. Mean elimination half-life was prolonged in uremic patients due to increased volume of distribution and reduced clearance. Dose initiation should follow a conservative approach. Dosages should be adjusted according to the clinical situation.

Ambulatory Patients:

Oxycodone hydrochloride tablets may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving a car or operating machinery. The patient using this drug should be cautioned accordingly.

Controlled Substance

Oxycodone hydrochloride tablets contains oxycodone, a mu-agonist opioid of the morphine type and is a Schedule II controlled substance. Oxycodone hydrochloride tablets, like other opioids used in analgesia, can be abused and is subject to criminal diversion.

Abuse

Drug addiction is characterized by compulsive use, use for non-medical purposes, and continued use despite harm or risk of harm. Drug addiction is a treatable disease, utilizing a multi-disciplinary approach, but relapse is common.

“Drug-seeking” behavior is very common in addicts and drug abusers. Drug-seeking tactics include emergency calls or visits near the end of office hours, refusal to undergo appropriate examination, testing or referral, repeated “loss” of prescriptions, tampering with prescriptions and reluctance to provide prior medical records or contact information for other treating physician(s). “Doctor shopping” to obtain additional prescriptions is common among drug abusers and people suffering from untreated addiction.

Abuse and addiction are separate and distinct from physical dependence and tolerance. Physicians should be aware that addiction may not be accompanied by concurrent tolerance and symptoms of physical dependence. In addition, abuse of opioids can occur in the absence of true addiction and is characterized by misuse for nonmedical purposes, often in combination with other psychoactive substances. Careful record-keeping of prescribing information, including quantity, frequency, and renewal requests is strongly advised.

Oxycodone hydrochloride tablets are intended for oral use only. Abuse of oxycodone hydrochloride tablets poses a risk of overdose and death. The risk is increased with concurrent abuse of alcohol and other substances. Parenteral drug abuse is commonly associated with transmission of infectious diseases such as hepatitis and HIV.

Proper assessment of the patient, proper prescribing practices, periodic re-evaluation of therapy, and proper dispensing and storage are appropriate measures that help to limit abuse of opioid drugs.

Infants born to mothers physically dependent on opioids will also be physically dependent and may exhibit respiratory difficulties and withdrawal symptoms.

Dependence

Tolerance is the need for increasing doses of opioids to maintain a defined effect such as analgesia (in the absence of disease progression or other external factors). Physical dependence is manifested by withdrawal symptoms after abrupt discontinuation of a drug or upon administration of an antagonist. Physical dependence and tolerance are not unusual during chronic opioid therapy.

The opioid abstinence or withdrawal syndrome is characterized by some or all of the following: restlessness, lacrimation, rhinorrhea, yawning, perspiration, chills, myalgia, and mydriasis. Other symptoms also may develop, including irritability, anxiety, backache, joint pain, weakness, abdominal cramps, insomnia, nausea, anorexia, vomiting, diarrhea, or increased blood pressure, respiratory rate, or heart rate. In general, opioids should not be abruptly discontinued.

Signs and Symptoms:

Acute overdose with oxycodone hydrochloride tablets can be manifested by respiratory depression, somnolence progressing to stupor or coma, skeletal muscle flaccidity, cold and clammy skin, constricted pupils, bradycardia, hypotension, and death.

Treatment:

To treat oxycodone hydrochloride tablets overdose, primary attention should be given to the re-establishment of a patent airway and institution of assisted or controlled ventilation. Supportive measures (including oxygen and vasopressors) should be employed in the management of circulatory shock and pulmonary edema accompanying overdose as indicated. Cardiac arrest or arrhythmias may require cardiac massage or defibrillation.

The narcotic antagonists, naloxone or nalmefene, are specific antidotes for opioid overdose. Opioid antagonists should not be administered in the absence of clinically significant respiratory or circulatory depression secondary to oxycodone hydrochloride tablets overdose. If needed the appropriate dose of naloxone hydrochloride or nalmefene should be administered simultaneously with efforts at respiratory resuscitation (see package insert for each drug for the details). Since the duration of action of oxycodone may exceed that of the antagonist, the patient should be kept under continued surveillance and repeated doses of the antagonist should be administered as needed to maintain adequate respiration. Gastric emptying may be useful in removing unabsorbed drug.

Opioid antagonists should be administered cautiously to persons who are suspected to be physically dependent on any opioid agonist, including oxycodone (see Opioid-Tolerant Individuals).

Conversion From Fixed-Ratio Opioid/Acetaminophen, Opioid/Aspirin, or Opioid/Nonsteroidal Combination Drugs:

When converting patients from fixed ratio opioid/non-opioid drug regimens a decision should be made whether or not to continue the non-opioid analgesic. If a decision is made to discontinue the use of non-opioid analgesic, it may be necessary to titrate the dose of oxycodone hydrochloride tablets in response to the level of analgesia and adverse effects afforded by the dosing regimen. If the non-opioid regimen is continued as a separate single entity agent, the starting dose oxycodone hydrochloride tablets should be based upon the most recent dose of opioid as a baseline for further titration of oxycodone. Incremental increases should be gauged according to side effects to an acceptable level of analgesia.

Patients Currently on Opioid Therapy:

If a patient has been receiving opioid-containing medications prior to taking oxycodone hydrochloride tablets, the potency of the prior opioid relative to oxycodone should be factored into the selection of the total daily dose (TDD) of oxycodone.

In converting patients from other opioids to oxycodone hydrochloride tablets close observation and adjustment of dosage based upon the patient's response to oxycodone hydrochloride tablets is imperative. Administration of supplemental analgesia for breakthrough or incident pain and titration of the total daily dose of oxycodone hydrochloride tablets may be necessary, especially in patients who have disease states that are changing rapidly.

Maintenance of Therapy:

Continual re-evaluation of the patient receiving oxycodone hydrochloride tablets is important, with special attention to the maintenance of pain control and the relative incidence of side effects associated with therapy. If the level of pain increases, effort should be made to identify the source of increased pain, while adjusting the dose as described above to decrease the level of pain.

During chronic therapy, especially for non-cancer-related pain (or pain associated with other terminal illnesses), the continued need for the use of opioid analgesics should be re-assessed as appropriate.

Cessation of Therapy:

When a patient no longer requires therapy with oxycodone hydrochloride tablets or other opioid analgesics for the treatment of their pain, it is important that therapy be gradually discontinued over time to prevent the development of an opioid abstinence syndrome (narcotic withdrawal). In general, therapy can be decreased by 25% to 50% per day with careful monitoring for signs and symptoms of withdrawal (see DRUG ABUSE AND DEPENDENCE section for description of the signs and symptoms of withdrawal). If the patient develops these signs or symptoms, the dose should be raised to the previous level and titrated down more slowly, either by increasing the interval between decreases, decreasing the amount of change in dose, or both. It is not known at what dose of oxycodone hydrochloride tablets that treatment may be discontinued without risk of the opioid abstinence syndrome.