Flanax Pain Reliever Side Effects
Generic name: naproxen
Medically reviewed by Drugs.com. Last updated on Oct 18, 2021.
Note: This document contains side effect information about naproxen. Some of the dosage forms listed on this page may not apply to the brand name Flanax Pain Reliever.
For the Consumer
Applies to naproxen: oral conventional and delayed-release tablets, oral extended-release tablets, oral suspension, oral tablets containing delayed-release naproxen and immediate-release esomeprazole, oral tablets containing naproxen sodium and sumatriptan
- Increased risk of serious (sometimes fatal) cardiovascular thrombotic events (e.g., MI, stroke).225 500 502 Risk may occur early in treatment and may increase with duration of use.225 500 502 505 506 (See Cardiovascular Thrombotic Effects under Cautions.)
- Contraindicated in the setting of CABG surgery.225
- Increased risk of serious (sometimes fatal) GI events (e.g., bleeding, ulceration, perforation of the stomach or intestine).225 Serious GI events can occur at any time and may not be preceded by warning signs and symptoms.225 Geriatric individuals and patients with a history of peptic ulcer disease and/or GI bleeding are at greater risk for serious GI events.225 (See GI Effects under Cautions.)
Side effects include:
For Healthcare Professionals
Applies to naproxen: compounding powder, oral capsule, oral delayed release tablet, oral suspension, oral tablet, oral tablet extended release, oral and topical kit
Common (1% to 10%): Diarrhea, abdominal pain
Very rare (less than 0.01%): Pancreatitis
Frequency not reported: Flatulence, gastritis, vomiting, dysphagia, stomatitis, abdomen enlarged, eructation, GI hemorrhage, rectal hemorrhage, aphthous, mouth ulcer, stomach ulcer, cardiospasm, colitis, esophagitis, gastroenteritis, GI disorder, rectal disorder, tooth disorder, melena esophageal ulcer, hematemesis, non-peptic GI ulceration, ulcerative stomatitis, sialadenitis, colitis
Rare (less than 0.1%): Hepatitis, jaundice
Very common (10% or more): Headache (15%)
Common (1% to 10%): Drowsiness, dizziness
Uncommon (0.1% to 1%): Cognitive dysfunction, poor concentration
Very rare (less than 0.01%): Convulsions, stroke
Very rare (less than 0.01%): Glomerular nephritis, interstitial nephritis, nephrotic syndrome, renal papillary necrosis
Frequency not reported: Kidney function abnormality, pyelonephritis, creatinine increased, glucosuria, albuminuria, BUN increased, renal failure, renal disease, kidney pain, nephrosclerosis, kidney failure, kidney calculus, nephropathy[Ref]
Uncommon (0.1% to 1%): Palpitations
Rare (0.01% to 0.1%): Vasculitis
Very rare (less than 0.01%): Arterial thrombotic events, myocardial infarction
Frequency not reported: Hypertension, angina pectoris, coronary artery disease, deep thrombophlebitis, vasodilation, vascular anomaly, arrhythmia, bundle branch block, abnormal ECG, right heart failure, hemorrhage, aortic stenosis, tachycardia, congestive heart failure
Postmarketing reports: Cardiac failure[Ref]
Rare (0.01% to 0.1%): Hemolytic anemia
Common (1% to 10%): Ecchymosis, rash, skin eruptions, pruritus, purpura
Uncommon (0.1% to 1%): Urticaria, photosensitivity
Frequency not reported: Angioneurotic edema/angioedema, angiodermatitis, dry skin, sweating, skin ulcer, acne, contact dermatitis, eczema, skin necrosis, subcutaneous nodule, photosensitive dermatitis, porphyria cutaneous tarda, nail disorder, epidermal necrosis, exfoliative dermatoses, bullous dermatoses, lichen planus
Postmarketing reports: Erythema nodosum, fixed drug eruption, pustular reaction, bullous reactions[Ref]
Rare (less than 0.1%): Aggravated asthma, eosinophilic pneumonitis
Frequency not reported: Bronchitis, cough increased, asthma, pulmonary edema, laryngitis, lung disorder, epistaxis, pneumonia, respiratory distress, respiratory disorder, bronchospasm, sore throat[Ref]
Very common (10% or more): Influenza-like syndrome (10%)
Common (1% to 10%): Infection, edema, tinnitus, fatigue
Rare (0.01% to 0.1%): Hearing impairment
Very rare (less than 0.01%): Aseptic meningitis
Frequency not reported: Fever, accidental injury, asthenia, chest pain, peripheral edema, hearing disturbances, thirst, abscess, cellulitis, malaise, mucous membrane disorder, periodontal abscess, necrosis, aseptic meningitis, chills, weight increased, otitis media, deafness, ear disorder, herpes simplex, herpes zoster, vertigo, subdural hematoma, exacerbation of Parkinson's disease[Ref]
Rare (less than 0.1%): Hyperkalemia
Postmarketing reports: Infertility[Ref]
The most frequently reported adverse events were headache, dyspepsia, nausea, constipation, heartburn, abdominal pain, and influenza-like syndrome.[Ref]
Common (1% to 10%): Urinary tract infection
Very rare (less than 0.01%): Hematuria
Frequency not reported: Cystitis, monilia, pelvic pain, dysmenorrhea, dysuria, nocturia, prostate disorder, urinary incontinence, menorrhagia, menstrual disorders, vaginitis, uterine spasm, urinary retention, urinary frequency, abnormal urine, pyuria, metrorrhagia[Ref]
Common (1% to 10%): Back pain
Rare (less than 0.1%): Myalgia, muscle weakness
Frequency not reported: Leg cramps, arthralgia, joint disorder, tendon disorder, neck rigid/pain, LE syndrome, myasthenia, bone disorder, spontaneous bone fracture, fibrotendinitis, bone pain, spasm, bursitis
Common (1% to 10%): Visual disturbances
Postmarketing reports: Corneal opacity, papillitis, papilledema[Ref]
Frequency not reported: Carcinoma, breast carcinoma, breast neoplasm, skin neoplasm[Ref]
Common (1% to 10%): Confusion
Uncommon (0.1% to 1%): Depression, dream abnormalities, mood alterations
Frequently asked questions
- Naproxen vs ibuprofen: What's the difference?
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More about Flanax Pain Reliever (naproxen)
- Drug interactions
- Dosage information
- During pregnancy or Breastfeeding
- Reviews (1)
- Imprints, shape & color data
- Drug class: Nonsteroidal anti-inflammatory drugs
Related treatment guides
1. "Product Information. Naprosyn (naproxen)." Syntex Laboratories Inc (2002):
2. "Product Information. Anaprox (naproxen)." Roche Laboratories (2006):
3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
4. Cerner Multum, Inc. "Australian Product Information." O 0
5. "Product Information. Naprelan 375 (naproxen)." Shionogi USA Inc (2010):
6. MHRA. Medicines and Health Regulatory Agency "MHRA Drug Safety Update. http://www.mhra.gov.uk/Safetyinformation/DrugSafetyUpdate." (2013):
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.