PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN

Apotheca, Inc.

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN TABLET USP 100MG/650MG CS-CIV

FULL PRESCRIBING INFORMATION: CONTENTS*

• WARNINGS
• PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN DESCRIPTION
• CLINICAL PHARMACOLOGY
  • Pharmacokinetics
  • SPECIAL POPULATIONS
• CLINICAL STUDIES
• PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN INDICATIONS AND USAGE
• PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN CONTRAINDICATIONS
• WARNINGS
  • Respiratory Depression
  • Hypotensive Effect
  • Head Injury and Increased Intracranial Pressure
  • Drug Interactions
  • Usage in Ambulatory Patients
  • Use With Other Acetaminophen-Containing Agents
  • Use With Alcohol
• PRECAUTIONS
  • Use in Pancreatic/Biliary Tract Disease
  • Hepatic or Renal Impairment
  • Information for Patients/Caregivers
  • Drug Interactions With Propoxyphene
  • Drug Interactions With Acetaminophen
  • Carcinogenesis, Mutagenesis, Impairment of Fertility
  • Pregnancy
  • Nursing Mothers
  • Pediatric Patients
  • Geriatric Patients
• PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN ADVERSE REACTIONS
• DRUG ABUSE AND DEPENDENCE
  • Abuse
  • Dependence
• OVERDOSAGE
  • Propoxyphene Overdosage
  • Acetaminophen Overdosage
• PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN DOSAGE AND ADMINISTRATION
  • Cessation of Therapy
• HOW SUPPLIED
• Storage and Dispensing
• MEDICATION GUIDE
• PACKAGE LABEL

FULL PRESCRIBING INFORMATION

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN DESCRIPTION

Propoxyphene napsylate and acetaminophen tablets USP contain propoxyphene napsylate and acetaminophen.

Propoxyphene napsylate is an odorless, white crystalline powder with a bitter taste. It is very slightly soluble in water, soluble in methanol, in ethanol, in chloroform, and in acetone. Chemically it is (αS,1R)-α-[2-(dimethylamino)-1-methylethyl]-α-phenylphenethyl propionate compound with 2-naphthalenesulfonic acid (1:1) monohydrate and can be represented by the following structural formula:

C₂₂H₂₉NO₂•C₁₀H₈O₃S•H₂O          M.W. 565.74

Propoxyphene napsylate differs from propoxyphene hydrochloride in that it allows more stable liquid dosage forms and tablet formulations. Because of differences in molecular weight, a dose of 100 mg (176.8 μmol) of propoxyphene napsylate is required to supply an amount of propoxyphene equivalent to that present in 65 mg (172.9 μmol) of propoxyphene hydrochloride.

Acetaminophen, 4'-hydroxyacetanilide, is a non-opiate, non-salicylate analgesic and antipyretic which occurs as a white, odorless, crystalline powder, possessing a slightly bitter taste. Chemically, it is acetamide, N-(4-hydroxyphenyl)- and can structurally be represented by the following:

C₈H₉NO₂          M.W. 151.16

Each pink tablet of propoxyphene napsylate and acetaminophen tablets contains 100 mg propoxyphene napsylate and 650 mg acetaminophen.

Propoxyphene napsylate and acetaminophen tablets, USP 100 mg/650 mg (PINK) contain the following inactive ingredients:

colloidal silicon dioxide,D and C red No 27 aluminum lake, D and C yellow No 10 aluminum lake, hydroxypropyl cellulose, hypromellose, magnesium stearate,
microcrystalline cellulose, polyethylene glycol, povidone, pregelatinized starch, stearic acid, titanium dioxide, and crospovidone.

CLINICAL PHARMACOLOGY

Propoxyphene is a centrally acting opiate analgesic. In vitro studies demonstrated propoxyphene and the metabolite norpropoxyphene inhibit sodium channels (local anesthetic effect) with norpropoxyphene being approximately 2 fold more potent than propoxyphene and propoxyphene approximately 10 fold more potent than lidocaine. Propoxyphene and norpropoxyphene inhibit the voltage-gated potassium current carried by cardiac rapidly activating delayed rectifier (hERG) channels with approximately equal potency. It is unclear if the effects on ion channels occur within therapeutic dose range.

Acetaminophen is a non-opiate, non-salicylate analgesic and antipyretic. The site and mechanism for the analgesic effect of acetaminophen has not been determined. The antipyretic effect of acetaminophen is mediated through activity in the hypothalamic heat-regulating centers. Acetaminophen inhibits prostaglandin synthetase. Therapeutic doses of acetaminophen have negligible effects on the cardiovascular or respiratory systems; however, toxic doses may cause circulatory failure and rapid, shallow breathing.

Pharmacokinetics

Peak plasma concentrations of propoxyphene are reached in 2 to 2.5 h. After a 65 mg oral dose of propoxyphene hydrochloride, peak plasma levels of 0.05 to 0.1 mcg/mL for propoxyphene and 0.1 to 0.2 mcg/mL for norpropoxyphene (major metabolite) are achieved. Repeated doses of propoxyphene at 6 h intervals lead to increasing plasma concentrations, with a plateau after the ninth dose at 48 h. Propoxyphene has a half-life of 6 to 12 h, whereas that of norpropoxyphene is 30 to 36 h.

Acetaminophen is absorbed from the gastrointestinal tract and has a plasma half-life of 1.25 to 3 h, which may be increased by liver damage and following overdosage.

SPECIAL POPULATIONS

After oral administration of propoxyphene in elderly patients (70 to 78 years), much longer half-lives of propoxyphene and norpropoxyphene have been reported (propropoxyphene 13 to 35 h, norpropoxyphene 22 to 41 h). In addition, the AUC was an average of 3 fold higher and the C_max was an average of 2.5 fold higher in the elderly when compared to a younger (20 to 28 years) population. Longer dosage intervals may be considered in the elderly because the metabolism of propoxyphene may be reduced in this patient population. After multiple oral doses of propoxyphene in elderly patients (70 to 78 years), the C_max of the metabolite (norpropoxyphene) was increased 5 fold.

CLINICAL STUDIES

The efficacy of propoxyphene in combination with acetaminophen was studied in seven single-dose, randomized, double-blind, placebo-controlled trials in patients with mild to severe postpartum pain. One of the studies demonstrated that both propoxyphene and acetaminophen in the combination contributed to a greater reduction in pain than acetaminophen and propoxyphene alone and that propoxyphene was superior to placebo.

There is insufficient information available to assess efficacy of propoxyphene in combination with acetaminophen in patients with chronic pain.

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN INDICATIONS AND USAGE

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN CONTRAINDICATIONS

Propoxyphene napsylate and acetaminophen tablets are contraindicated in patients with known hypersensitivity to propoxyphene or acetaminophen.

Propoxyphene napsylate and acetaminophen tablets are contraindicated in patients with significant respiratory depression (in unmonitored settings or the absence of resuscitative equipment) and patients with acute or severe asthma or hypercarbia.

Propoxyphene napsylate and acetaminophen tablets are contraindicated in any patient who has or is suspected of having paralytic ileus.

WARNINGS

There have been numerous cases of accidental and intentional overdose with propoxyphene products either alone or in combination with other CNS depressants, including alcohol. Fatalities within the first hour of overdosage are not uncommon. Many of the propoxyphene-related deaths have occurred in patients with previous histories of emotional disturbances or suicidal ideation/attempts and/or concomitant administration of sedatives, tranquilizers, muscle relaxants, antidepressants, or other CNS-depressant drugs. Do not prescribe propoxyphene for patients who are suicidal or have a history of suicidal ideation.

Respiratory Depression

Hypotensive Effect

Head Injury and Increased Intracranial Pressure

Drug Interactions

Usage in Ambulatory Patients

Use With Other Acetaminophen-Containing Agents

Use With Alcohol

PRECAUTIONS

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 (see DOSAGE AND ADMINISTRATION, Cessation of Therapy).

If propoxyphene napsylate and acetaminophen tablets are 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 propoxyphene napsylate and acetaminophen tablets combined with symptomatic support (see DOSAGE AND ADMINISTRATION, Cessation of Therapy).

Use in Pancreatic/Biliary Tract Disease

Hepatic or Renal Impairment

Information for Patients/Caregivers

• Patients should be advised to report pain and adverse experiences occurring during therapy. Individualization of dosage is essential to make optimal use of this medication.
• Patients should be advised not to adjust the dose of propoxyphene napsylate and acetaminophen tablets without consulting the prescribing professional.
• Patients should be advised that propoxyphene napsylate and acetaminophen tablets may impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery).
• Patients should not combine propoxyphene napsylate and acetaminophen tablets with central nervous system depressants (e.g., sleep aids, tranquilizers) except by the orders of the prescribing physician, because additive effects may occur.
• Patients should be instructed not to consume alcoholic beverages, including prescription and over-the-counter medications that contain alcohol, while using propoxyphene napsylate and acetaminophen tablets because of risk of serious adverse events including death.
• 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.
• Patients should be advised that propoxyphene napsylate and acetaminophen 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.
• Patients should be advised that if they have been receiving treatment with propoxyphene napsylate and acetaminophen tablets for more than a few weeks and cessation of therapy is indicated, it may be appropriate to taper the propoxyphene napsylate and acetaminophen tablet 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.
• Instruct patients not to consume any other medication that contain acetaminophen, including acetaminophen-based over-the-counter medications, while taking propoxyphene napsylate and acetaminophen tablets.

Drug Interactions With Propoxyphene

Propoxyphene is metabolized mainly via the human cytochrome P450 3A4 isoenzyme system (CYP3A4), therefore potential interactions may occur when propoxyphene is administered concurrently with agents that affect CYP3A4 activity.

The metabolism of propoxyphene may be altered by strong CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, troleandomycin, clarithromycin, nelfinavir, nefazadone, amiodarone, amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, grapefruit juice, and verapamil) leading to enhanced propoxyphene plasma levels. Coadministration with agents that induce CYP3A4 activity may reduce the efficacy of propoxyphene. Strong CYP3A4 inducers such as rifampin may lead to enhanced metabolite (norpropoxyphene) levels.

Propoxyphene is also thought to possess CYP3A4 and CYP2D6 enzyme inhibiting properties and coadministration with drugs that rely on either of these enzymes for metabolism may result in increased pharmacologic or adverse effects of that drug. Severe neurologic signs, including coma, have occurred with concurrent use of carbamazepine (metabolized by CYP3A4).

Increased risk of bleeding has been observed with warfarin-like agents when given along with propoxyphene; however, the mechanistic basis of this interaction is unknown.

Drug Interactions With Acetaminophen

Alcohol: Hepatotoxicity has occurred in chronic alcoholics following various dose levels (moderate to excessive) of acetaminophen.

Anticholinergics: The onset of acetaminophen effect may be delayed or decreased slightly, but the ultimate pharmacological effect is not significantly affected by anticholinergics.

Oral Contraceptives: Increase in glucuronidation resulting in increased plasma clearance and a decreased half-life of acetaminophen.

Beta Blockers (Propranolol): Propranolol appears to inhibit the enzyme systems responsible for the glucuronidation and oxidation of acetaminophen. Therefore, the pharmacologic effects of acetaminophen may be increased.

Loop Diuretics: The effects of the loop diuretic may be decreased because acetaminophen may decrease renal prostaglandin excretion and decrease plasma renin activity.

Lamotrigine: Serum lamotrigine concentrations may be reduced, producing a decrease in therapeutic effects.

Probenecid: Probenecid may increase the therapeutic effectiveness of acetaminophen slightly.

Zidovudine: The pharmacologic effects of zidovudine may be decreased because of enhanced nonhepatic or renal clearance of zidovudine.

Carcinogenesis, Mutagenesis, Impairment of Fertility

The mutagenic and carcinogenic potential of propoxyphene and acetaminophen alone and in combination have not been evaluated.

In animal studies there was no effect of propoxyphene on mating behavior, fertility, duration of gestation, or parturition when rats were fed propoxyphene as a component of their daily diet at estimated daily propoxyphene intake up to 8 fold greater than the maximum human equivalent dose (HED) based on body surface area comparison. At this highest dose, fetal weight and survival on postnatal day 4 was reduced. Acetaminophen has not been studied in animals for effects on fertility and the effects on human fertility are unknown.

Pregnancy

Nursing Mothers

Pediatric Patients

Geriatric Patients

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN ADVERSE REACTIONS

During clinical trials, the most frequently reported adverse reactions were dizziness, sedation, nausea, and vomiting. Other adverse reactions include constipation, abdominal pain, skin rashes, lightheadedness, headache, weakness, euphoria, dysphoria, hallucinations, and minor visual disturbances.

The most frequently reported postmarketing adverse events have included completed suicide, accidental and intentional overdose, drug dependence, cardiac arrest, coma, drug ineffective, drug toxicity, nausea, respiratory arrest, cardio-respiratory arrest, death, vomiting, dizziness, convulsion, confusional state, and diarrhea.

Additional adverse experiences reported through postmarketing surveillance include:

Cardiac disorders: arrhythmia, bradycardia, cardiac/respiratory arrest, congestive arrest, congestive heart failure (CHF), tachycardia, myocardial infarction (MI)

Eye disorder: eye swelling, vision blurred

General disorder and administration site conditions: drug ineffective, drug interaction, drug tolerance, influenza type illness, drug withdrawal syndrome

Gastrointestinal disorder: gastrointestinal bleed, acute pancreatitis

Hepatobiliary disorder: hepatic steatosis, hepatomegaly, hepatocellular injury

Immune system disorder: hypersensitivity

Injury poisoning and procedural complications: drug toxicity, hip fracture, multiple drug overdose, narcotic overdose

Investigations: blood pressure decreased, heart rate elevated/abnormal

Metabolism and nutrition disorder: metabolic acidosis

Nervous system disorder: ataxia, coma, dizziness, somnolence, syncope

Psychiatric: abnormal behavior, confusional state, hallucinations, mental status change

Respiratory, thoracic, and mediastinal disorders: respiratory depression, dyspnoea

Skin and subcutaneous tissue disorder: rash, itch

Liver dysfunction has been reported in association with both active components of propoxyphene napsylate and acetaminophen tablets. Propoxyphene therapy has been associated with abnormal liver function tests and, more rarely, with instances of reversible jaundice (including cholestatic jaundice). Hepatic necrosis may result from acute overdose of acetaminophen (see OVERDOSAGE). In chronic ethanol abusers, this has been reported rarely with short-term use of acetaminophen dosages of 2.5 to 10 g/day. Fatalities have occurred.

There have also been postmarketing reports of renal papillary necrosis associated with chronic acetaminophen use, particularly when the dosage is greater than recommended and when combined with aspirin. Subacute painful myopathy has been reported following chronic propoxyphene overdosage.

DRUG ABUSE AND DEPENDENCE

Propoxyphene napsylate and acetaminophen tablets are a Schedule IV narcotic under the U.S. Controlled Substances Act. Propoxyphene napsylate and acetaminophen tablets can produce drug dependence of the morphine type, and therefore, has the potential for being abused. Psychic dependence, physical dependence and tolerance may develop upon repeated administration. Propoxyphene napsylate and acetaminophen tablets should be prescribed and administered with the same degree of caution appropriate to the use of other narcotic-containing medications.

Abuse

Dependence

Opioid analgesics may cause psychological and physical dependence. Physical dependence results in withdrawal symptoms in patients who abruptly discontinue the drug after long term administration. Also, symptoms of withdrawal may be precipitated through the administration of drugs with mu-opioid antagonist activity, e.g., naloxone or mixed agonist/antagonist analgesics (pentazocine, butorphanol, nalbuphine, dezocine) (see OVERDOSAGE). Physical dependence usually does not occur to a clinically significant degree, until after several weeks of continued opioid usage. Tolerance, in which increasingly larger doses are required to produce the same degree of analgesia, is initially manifested by a shortened duration of an analgesic effect and subsequently, by decreases in the intensity of analgesia.

In chronic pain patients, and in opioid-tolerant cancer patients, the administration of propoxyphene napsylate and acetaminophen tablets should be guided by the degree of tolerance manifested and the doses needed to adequately relieve pain.

The severity of the propoxyphene napsylate and acetaminophen tablets abstinence syndrome may depend on the degree of physical dependence. Withdrawal is characterized by rhinitis, myalgia, abdominal cramping, and occasional diarrhea. Most observable symptoms disappear in 5 to 14 days without treatment; however, there may be a phase of secondary or chronic abstinence which may last for 2 to 6 months characterized by insomnia, irritability, and muscular aches. The patient may be detoxified by gradual reduction of the dose. Gastrointestinal disturbances or dehydration should be treated with supportive care

OVERDOSAGE

Propoxyphene napsylate and acetaminophen tablets are a combination product containing propoxyphene and acetaminophen. Overdose of propoxyphene napsylate and acetaminophen tablets may present with the signs and symptoms of propoxyphene overdose, acetaminophen overdose or both. Fatalities within the first hour of overdosage are not uncommon.

In all cases of suspected overdosage, call your regional Poison Control Center to obtain the most up-to-date information about the treatment of overdose. This recommendation is made because, in general, information regarding the treatment of overdosage may change more rapidly than do package inserts.

Initial consideration should be given to the management of the CNS effects of propoxyphene overdosage. Resuscitative measures should be initiated promptly.

Propoxyphene Overdosage

The manifestations of acute overdosage with propoxyphene are those of opioid overdosage. The patient is usually somnolent but may be stuporous or comatose and convulsing. Respiratory depression is characteristic. The ventilatory rate and/or tidal volume is decreased, which results in cyanosis and hypoxia. Pupils, initially pinpoint, may become dilated as hypoxia increases. Cheyne-Stokes respiration and apnea may occur. Blood pressure and heart rate are usually normal initially, but blood pressure falls and cardiac performance deteriorates, which ultimately results in pulmonary edema and circulatory collapse, unless the respiratory depression is corrected and adequate ventilation is restored promptly. Cardiac arrhythmias and conduction delay may be present. A combined respiratory-metabolic acidosis occurs owing to retained CO₂ (hypercapnia) and to lactic acid formed during anaerobic glycolysis. Acidosis may be severe if large amounts of salicylates have also been ingested. Death may occur.

Acetaminophen Overdosage

Overdose of acetaminophen may cause dose-dependent potentially fatal hepatic toxicity. Early symptoms within 24 hours after the overdose may include anorexia, nausea, vomiting, diaphoresis, general malaise, and abdominal pain. The patient may then present no symptoms, but evidence of liver dysfunction may become apparent up to 72 hours after ingestion, with elevated serum transaminase and lactic dehydrogenase levels, an increase in serum bilirubin concentrations, and a prolonged prothrombin time. Death from hepatic failure may result 3 to 7 days after overdosage.

Because clinical and laboratory evidence of hepatic toxicity may not be apparent until 48 to 72 hours post-ingestion, liver function studies should be obtained initially and repeated at 24 hour intervals.

Acute renal failure may accompany the hepatic dysfunction and has been noted in patients who do not exhibit signs of fulminant hepatic failure. Typically, renal impairment is more apparent 6 to 9 days after ingestion of the overdose.

In all cases of suspected overdose, immediately call the Rocky Mountain Poison Center's toll-free number (800-525-6115) for assistance in diagnosis and for directions in the use of N-acetylcysteine as an antidote.

Patients' estimates of the quantity of a drug ingested are notoriously unreliable. Therefore, if an acetaminophen overdose is suspected, a serum acetaminophen assay should be obtained as early as possible, but no sooner than 4 hours following ingestion. The antidote, N-acetylcysteine, should be administered as early as possible, and within 16 hours of the overdose ingestion for optimal results.

PROPOXYPHENE NAPSYLATE AND ACETAMINOPHEN DOSAGE AND ADMINISTRATION

Proproxyphene napsylate and acetaminophen tablets USP are intended for the management of mild to moderate pain. The dose should be individually adjusted according to severity of pain, patient response and patient size.

Propoxyphene napsylate and acetaminophen tablets USP (100 mg propoxyphene napsylate and 650 mg acetaminophen)

The usual dosage is one tablet every 4 hours orally as needed for pain. The maximum dose of propoxyphene napsylate and acetaminophen tablets USP is 6 tablets per day. Do not exceed the maximum daily dose.

Patients receiving propoxyphene and any CYP3A4 inhibitor should be carefully monitored for an extended period of time and dosage adjustments should be made if warranted.

Consideration should be given to a reduced total daily dosage in elderly patients and in patients with hepatic or renal impairment.

Cessation of Therapy

HOW SUPPLIED

• 12634-534-91 Blister Pack UD of 1
• 12634-537-69 Blister Pack Card of 9
• 12634-537-55 Blister Pack Card of 15
• 12634-537-98 Bottle of 8
• 12634-537-00 Bottle of 10
• 12634-537-82 Bottle of 12
• 12634-537-85 Bottle of 15
• 12634-537-80 Bottle of 20
• 12634-537-71 Bottle of 30
• 12634-537-60 Bottle of 60
• 12634-537-01 Bottle of 100

Storage and Dispensing

Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].

Inform patients of the availability of a Medication Guide for propoxyphene napsylate and acetaminophen tablets USP that accompanies each prescription dispensed. Instruct patients to read the propoxyphene napsylate and acetaminophen Medication Guide prior to using propoxyphene napsylate and acetaminophen tablets USP.

Dispense in a tight, light-resistant container as defined in the USP, using a child-resistant closure.

MEDICATION GUIDE

PACKAGE LABEL