Acetaminophen, dichloralphenazone, and isometheptene

Name: Acetaminophen, dichloralphenazone, and isometheptene

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of acetaminophen can damage your liver or cause death.

The first signs of an acetaminophen overdose include loss of appetite, nausea, vomiting, stomach pain, sweating, and confusion or weakness. Later symptoms may include pain in your upper stomach, dark urine, and yellowing of your skin or the whites of your eyes.

Acetaminophen, dichloralphenazone, and isometheptene dosing information

Usual Adult Dose for Headache:

Migraine Headache: 2 capsules at once orally, followed by one capsule every hour until relieved, up to 5 capsules within a 12 hour period

Tension Headache: 1 to 2 capsules every 4 hours, up to 8 capsules a day

For the Consumer

Applies to acetaminophen / dichloralphenazone / isometheptene mucate: oral capsule

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
  • Not able to pass urine or change in how much urine is passed.
  • A very bad skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may happen. It can cause very bad health problems that may not go away, and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.

For Healthcare Professionals

Applies to acetaminophen / dichloralphenazone / isometheptene mucate: oral capsule

Hypersensitivity

Transient dizziness and skin rash can usually be eliminated by reducing the dose of acetaminophen/dichloralphenazone/isometheptene.[Ref]

Hypersensitivity side effects including transient dizziness and skin rash have been reported with the use of acetaminophen/dichloralphenazone/isometheptene. Hypersensitivity reactions, including anaphylaxis and fixed drug eruptions have been reported rarely in association with acetaminophen use.[Ref]

Hepatic

Alcoholic patients may develop hepatotoxicity after even modest doses of acetaminophen. In healthy patients, approximately 15 grams of acetaminophen is necessary to deplete liver glutathione stores by 70% in a 70 kg person. However, hepatotoxicity has been reported following smaller doses. Glutathione concentrations may be repleted by the antidote N-acetylcysteine. One case report has suggested that hypothermia may also be beneficial in decreasing liver damage during overdose.

In a recent retrospective study of 306 patients admitted for acetaminophen overdose, 6.9% had severe liver injury but all recovered. None of the 306 patients died.

One study has suggested that acetaminophen may precipitate acute biliary pain and cholestasis. The mechanism of this effect may be related to inhibition of prostaglandin and alterations in the regulation of the sphincter of Oddi.

Cases of acute pancreatitis have been reported rarely with the use of acetaminophen.[Ref]

Hepatic side effects including severe and sometimes fatal dose dependent hepatitis have been reported with the use of acetaminophen in alcoholic patients. Hepatotoxicity has been increased during fasting.[Ref]

Gastrointestinal

Gastrointestinal side effects have been rare with the use of acetaminophen except in alcoholics and after overdose.[Ref]

Renal

Renal side effects including acute tubular necrosis and interstitial nephritis have been rare with the use of acetaminophen. Adverse renal effects have been most often observed after overdose, after chronic abuse (often with multiple analgesics), or in association with acetaminophen-related hepatotoxicity.[Ref]

Acute tubular necrosis with acetaminophen use usually occurs in conjunction with liver failure, but has been observed as an isolated finding in rare cases. A possible increase in the risk of renal cell carcinoma has been associated with chronic acetaminophen use as well.

A recent case-control study of patients with end-stage renal disease suggested that long term consumption of acetaminophen may significantly increase the risk of end-stage renal disease particularly in patients taking more than two pills per day.[Ref]

Hematologic

Hematologic side effects including rare cases of thrombocytopenia associated with acetaminophen have been reported. Methemoglobinemia with resulting cyanosis has also been observed in the setting of acute overdose.[Ref]

Dermatologic

Dermatologic side effects including erythematous skin rashes associated with acetaminophen have been reported rarely. Acetaminophen associated bullous erythema and purpura fulminans have also been reported.[Ref]

Respiratory

Respiratory side effects including a case of acetaminophen-induced eosinophilic pneumonia have been reported.[Ref]

Cardiovascular

Cardiovascular side effects including at least two cases of hypotension have been reported following the administration of acetaminophen.[Ref]

Two cases hypotension have been reported following the administration of acetaminophen. Both patients experienced significant decreases in blood pressure. One of the two patients required pressor agents to maintain adequate mean arterial pressures. Neither episode was associated with symptoms of anaphylaxis. Neither patient was rechallenged after resolution of the initial episode.[Ref]

Some side effects of acetaminophen / dichloralphenazone / isometheptene mucate may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Acetaminophen / dichloralphenazone / isometheptene mucate Breastfeeding Warnings

One small study on acetaminophen has reported that following a 1000 mg dose of acetaminophen to nursing mothers, nursing infants receive less than 1.85% of the weight-adjusted maternal oral dose.

Acetaminophen is excreted into human milk in small concentrations. One case of a rash has been reported in a nursing infant. Acetaminophen is considered compatible with breast-feeding by the American Academy of Pediatrics. Dichloralphenazone is a prodrug composed of phenazone and chloral hydrate. Both phenazone and the active metabolite of chloral hydrate, trichloroethanol, are excreted into human milk. Milk concentrations of trichoroethanol have been reported at 60% to 80% of maternal serum levels. The only effect reported in the infant was mild morning drowsiness. There are no data on the excretion of isometheptene into human milk.

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