Benadryl Allergy Plus Cold Side Effects

Generic Name: acetaminophen / diphenhydramine / phenylephrine

Note: This document contains side effect information about acetaminophen / diphenhydramine / phenylephrine. Some of the dosage forms listed on this page may not apply to the brand name Benadryl Allergy Plus Cold.

Some side effects of Benadryl Allergy Plus Cold may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to acetaminophen / diphenhydramine / phenylephrine: powder packet, suspension, tablets

Other dosage forms:

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Constipation; diarrhea; dizziness; drowsiness; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness.

Seek medical attention right away if any of these SEVERE side effects occur while taking acetaminophen / diphenhydramine / phenylephrine:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); dark urine; difficulty urinating or inability to urinate; fast or irregular heartbeat; hallucinations; mood or mental changes; pale stools; seizures; severe drowsiness; severe or persistent dizziness, nervousness, lightheadedness, or headache; severe or persistent trouble sleeping; stomach pain; tremor; vision changes; yellowing of skin or eyes.

For Healthcare Professionals

Applies to acetaminophen / diphenhydramine / phenylephrine: oral liquid, oral powder for reconstitution, oral syrup, oral tablet

Cardiovascular

Cardiovascular side effects of acetaminophen have included two cases of hypotension.

Cardiovascular side effects of diphenhydramine have included hypotension, tachycardia, and palpitations.

Cardiovascular side effects of phenylephrine have included palpitations, arrhythmias, and cardiovascular collapse with hypotension.

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.

Dermatologic

Dermatologic side effects have included erythematous skin rashes. Acetaminophen associated bullous erythema and purpura fulminans have also been reported. Acetaminophen has been associated with a risk of rare but potentially fatal serious skin reactions known as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP).

Gastrointestinal

Gastrointestinal side effects of acetaminophen have included rare cases of acute pancreatitis.

Gastrointestinal side effects of diphenhydramine have included nausea and dry mouth.

Gastrointestinal side effects of phenylephrine have included nausea.

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.

Genitourinary

Genitourinary side effects of diphenhydramine have included urinary retention and dysuria.

Genitourinary side effects of phenylephrine have included dysuria.

Hematologic

Hematologic side effects of acetaminophen have included rare cases of thrombocytopenia. Methemoglobinemia with resulting cyanosis has also been observed in the setting of acute overdose.

Hematologic side effects of diphenhydramine have rarely included hemolytic anemia, thrombocytopenia, and agranulocytosis.

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.

A 19 year old female developed hepatotoxicity, reactive plasmacytosis and agranulocytosis followed by a leukemoid reaction after acute acetaminophen toxicity.

Hepatic side effects of acetaminophen have included severe and sometimes fatal dose dependent hepatitis in alcoholic patients. Hepatotoxicity has been increased during fasting. Several cases of hepatotoxicity from chronic acetaminophen therapy at therapeutic doses have also been reported despite a lack of risk factors for toxicity.

Hypersensitivity

Hypersensitivity side effects of acetaminophen have included rare reports of anaphylaxis and fixed drug eruptions.

Hypersensitivity side effects to diphenhydramine have included rash, pruritus and eczema. Photosensitivity reactions have also been reported.

Most commonly, hypersensitivity to diphenhydramine has manifested itself in patients receiving systemic drug after being sensitized to it by topical application. Sensitization with systemic administration has also been reported.

Nervous system

Nervous system side effects of diphenhydramine have included depression with drowsiness and sedation in nearly all patients treated. Motor skills may be impaired. Dystonic reactions have been reported after single doses of diphenhydramine.

Nervous system side effects of phenylephrine have included headache, dizziness, nervousness, restlessness, tremor, insomnia, convulsions, and central nervous system depression.

The CNS depressant effect of diphenhydramine parallels its plasma concentrations. The plasma concentration threshold for sedation is 30 to 42 ng/mL, and to cause mental impairment is 58 to 74 ng/mL. Patients should be warned against driving while taking diphenhydramine.

Dystonic reactions have been accompanied by dizziness, mental confusion, rigidity, lip and tongue protrusion, trismus, torticollis, and swallowing difficulties and generally resolve spontaneously. Toxic encephalopathy has been reported in a child with chicken pox treated generously with topical diphenhydramine.

Delirium has been reported in elderly patients with mild dementia following a small oral dose of diphenhydramine.

Renal

Renal side effects of acetaminophen have included acute tubular necrosis and interstitial nephritis. Adverse renal effects are most often observed after overdose, after chronic abuse (often with multiple analgesics), or in association with acetaminophen-related hepatotoxicity.

Acute tubular necrosis 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.

Respiratory

Respiratory side effects of acetaminophen have included a case of eosinophilic pneumonia.

Respiratory side effects of phenylephrine have included respiratory difficulty.

Psychiatric

Psychiatric side effects of phenylephrine have included hallucinations, fear, and anxiety.

General

General side effects of phenylephrine have included pallor and weakness.

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