Components:
Medically reviewed by Fedorchenko Olga Valeryevna, PharmD. Last updated on 22.03.2022
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Flexib is indicated:
- For relief of the signs and symptoms of osteoarthritis.
- For relief of the signs and symptoms of rheumatoid arthritis in adults.
- For relief of the signs and symptoms of pauciarticular or polyarticular course Juvenile Rheumatoid Arthritis (JRA) in patients 2 years and older and who weigh 10 kg (22 lbs) or more.
- For the management of acute pain in adults.
- For the treatment of primary dysmenorrhea.
- For the acute treatment of migraine attacks with or without aura in adults.
The safety and effectiveness of Flexib have not been established for cluster headache, which is present in an older, predominantly male, population.
Flexib was withdrawn from the U.S. market in 2004.
Flexib is in a class of drugs called nonsteroidal anti-inflammatory drugs (NSAIDs). Flexib works by reducing substances that cause inflammation, pain, and fever in the body.
Flexib is used to reduce pain, inflammation, and stiffness caused by osteoarthritis, rheumatoid arthritis and certain forms of juvenile rheumatoid arthritis; to manage acute pain in adults; to treat migraines; and to treat menstrual pain.
Flexib may also be used for purposes other than those listed in this medication guide.
Flexib is administered orally. Use the lowest effective dosage for the shortest duration consistent with individual patient treatment goals.
Osteoarthritis
The recommended starting dose of Flexib is 12.5 mg once daily. Some patients may receive additional benefit by increasing the dose to 25 mg once daily. The maximum recommended daily dose is 25 mg.
Rheumatoid Arthritis
The recommended dose is 25 mg once daily. The maximum recommended daily dose is 25 mg.
Pauciarticular and Polyarticular Course Juvenile Rheumatoid Arthritis
| Pediatric Patients | Daily Dose |
| ≥ 2 years to ≤ 11 years of age and ≥ 10 to < 42 kg | 0.6 mg/kg to a maximum of 25 mg* |
| ≥ 2 years to ≤ 11 years of age and ≥ 42 kg | 25 mg |
| ≥ 12 years to ≤ 17 years of age | 25 mg |
| *Oral suspension dosage form is recommended. To improve dosing accuracy in smaller weight children, the use of 12.5 mg/5 mL oral suspension (2.5 mg/mL) is recommended. |
Management Of Acute Pain And Treatment Of Primary Dysmenorrhea
The recommended dose of Flexib is 50 mg once daily. The maximum recommended daily dose is 50 mg. Use of Flexib for more than 5 days in management of pain has not been studied. Chronic use of Flexib 50 mg daily is not recommended..
Acute Treatment Of Migraine Attacks With Or Without Aura
The recommended starting dose of Flexib is 25 mg once daily. Some patients may receive additional benefit with 50 mg as compared to 25 mg. The maximum recommended daily dose is 50 mg. The safety of treating more than 5 migraine attacks in any given month has not been established. Chronic daily use of Flexib for the acute treatment of migraine is not recommended.
Hepatic Impairment
Because of significant increases in both AUC and Cmax in patients with moderate hepatic impairment (Child-Pugh score: 7-9), the maximum recommended chronic daily dose is 12.5 mg.. The efficacy of 12.5 mg in rheumatoid arthritis patients with moderate hepatic insufficiency has not been studied. Use of Flexib is not recommended in patients with severe hepatic insufficiency.
Flexib Tablets may be taken with or without food.
Oral Suspension
Flexib
Oral Suspension 12.5 mg/5 mL or 25 mg/5 mL may be substituted for Flexib Tablets 12.5 or 25 mg, respectively, in any of the above indications. Shake before using.
How supplied
No. 3810 — Tablets Flexib, 12.5 mg, are cream/off-white, round, shallow cup tablets engraved MRK 74 on one side and Flexib on the other. They are supplied as follows:
NDC 0006-0074-31 unit of use bottles of 30
NDC 0006-0074-28 unit dose packages of 100
NDC 0006-0074-68 bottles of 100
NDC 0006-0074-82 bottles of 1000
NDC 0006-0074-80 bottles of 8000.
No. 3834 — Tablets Flexib, 25 mg, are yellow, round tablets engraved MRK 110 on one side andVIOXX on the other. They are supplied as follows:
NDC 0006-0110-31 unit of use bottles of 30
NDC 0006-0110-28 unit dose packages of 100
NDC 0006-0110-68 bottles of 100
NDC 0006-0110-82 bottles of 1000
NDC 0006-0110-80 bottles of 8000.
No. 3835 — Tablets Flexib, 50 mg, are orange, round tablets engraved MRK 114 on one side andVIOXX on the other. They are supplied as follows:
NDC 0006-0114-31 unit of use bottles of 30
NDC 0006-0114-28 unit dose packages of 100
NDC 0006-0114-68 bottles of 100
NDC 0006-0114-74 bottles of 500
NDC 0006-0114-81 bottles of 4000.
No. 3784 —
Oral Suspension Flexib, 12.5 mg/5 mL
NDC 0006-3784-64 unit of use bottles containing 150 mL (12.5 mg/5 mL).
No. 3785 —
Oral Suspension Flexib, 25 mg/5 mL
NDC 0006-3785-64 unit of use bottles containing 150 mL (25 mg/5 mL).
Storage
Flexib Tablets
Store at 25°C (77°F), excursions permitted to 15-30°C (59-86°F).
Flexib
Oral Suspension
Store at 25°C (77°F), excursions permitted to 15-30°C (59-86°F).
Merck Sharp & Dohme Corp., a subsidiary of MERCK & CO., INC., Whitehouse Station, NJ 08889, USA.
See also:
What is the most important information I should know about Flexib?
Flexib is contraindicated in the following patients:
- Known hypersensitivity (e.g., anaphylactic reactions and serious skin reactions) to Flexib or any components of the drug product..
- History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. Severe, sometimes fatal, anaphylactic reactions to NSAIDs have been reported in such patients.
- In the setting of coronary artery bypass graft (CABG) surgery.
Flexib is used to relieve the pain and inflammation of osteoarthritis (a type of joint disease that causes stiffness, pain and loss of joint movement) and rheumatoid arthritis (inflammatory disorder that typically affects the small joints in hands and feet). It is also used to treat menstrual pain, migraine headache attacks with or without aura.
See also:
What other drugs will affect Flexib?
Table 6: Clinically Significant Drug Interactions with Flexib
| Drugs That Interfere with Hemostasis | |
| Clinical Impact: |
|
| Intervention: |
|
| Aspirin | |
| Clinical Impact: | Controlled clinical studies showed that the concomitant use of NSAIDs and analgesic doses of aspirin does not produce any greater therapeutic effect than the use of NSAIDs alone. In a clinical study, the concomitant use of an NSAID and aspirin was associated with a significantly increased incidence of GI adverse reactions as compared to use of the NSAID alone.. Concomitant administration of low-dose aspirin with Flexib may result in an increased rate of GI ulceration or other complications, compared to use of Flexib alone. In a 12-week endoscopy study conducted in OA patients there was no difference in the cumulative incidence of endoscopic gastroduodenal ulcers in patients taking low-dose (81 mg) enteric coated aspirin plus Flexib 25 mg daily, as compared to those taking ibuprofen 2400 mg daily alone. Patients taking low-dose aspirin plus ibuprofen were not studied. At steady state, Flexib 50 mg once daily had no effect on the anti-platelet activity of low-dose (81 mg once daily) aspirin, as assessed by ex vivo platelet aggregation and serum TXB2 generation in clotting blood. Because of its lack of platelet effects, Flexib is not a substitute for aspirin for cardiovascular prophylaxis. Prospective, long-term studies on concomitant administration of Flexib and aspirin have not been conducted. |
| Intervention: |
|
| ACE Inhibitors, Angiotensin Receptor Blockers, and Beta-Blockers | |
| Clinical Impact: |
|
| Intervention: |
|
| Diuretics | |
| Clinical Impact: | Clinical studies, as well as post-marketing observations, showed that NSAIDs reduced the natriuretic effect of loop diuretics (e.g., furosemide) and thiazide diuretics in some patients. This effect has been attributed to the NSAID inhibition of renal prostaglandin synthesis. |
| Intervention: | During concomitant use of Flexib with diuretics, observe patients for signs of worsening renal function, in addition to assuring diuretic efficacy including antihypertensive effects. |
| Digoxin | |
| Clinical Impact: | The concomitant use of Flexib with digoxin has been reported to increase the serum concentration and prolong the half-life of digoxin. |
| Intervention: | During concomitant use of Flexib and digoxin, monitor serum digoxin levels. |
| Lithium | |
| Clinical Impact: | NSAIDs have produced elevations in plasma lithium levels and reductions in renal lithium clearance. The mean minimum lithium concentration increased 15%, and the renal clearance decreased by approximately 20%. This effect has been attributed to NSAID inhibition of renal prostaglandin synthesis. In post-marketing experience there have been reports of increases in plasma lithium levels when Flexib and lithium were administered concurrently. |
| Intervention: | During concomitant use of Flexib and lithium, monitor patients for signs of lithium toxicity. |
| Methotrexate | |
| Clinical Impact: | Concomitant use of NSAIDs and methotrexate may increase the risk for methotrexate toxicity (e.g., neutropenia, thrombocytopenia, renal dysfunction). |
| Intervention: | During concomitant use of Flexib and methotrexate, monitor patients for methotrexate toxicity. |
| Cyclosporine | |
| Clinical Impact: | Concomitant use of Flexib and cyclosporine may increase cyclosporine’s nephrotoxicity. |
| Intervention: | During concomitant use of Flexib and cyclosporine, monitor patients for signs of worsening renal function. |
| NSAIDs and Salicylates | |
| Clinical Impact: | Concomitant use of Flexib with other NSAIDs or salicylates (e.g., diflunisal, salsalate) increases the risk of GI toxicity, with little or no increase in efficacy. |
| Intervention: | The concomitant use of Flexib with other NSAIDs or salicylates is not recommended. |
| Pemetrexed | |
| Clinical Impact: | Concomitant use of Flexib and pemetrexed may increase the risk of pemetrexed-associated myelosuppression, renal, and GI toxicity. |
| Intervention: | During concomitant use of Flexib and pemetrexed, in patients with renal impairment whose creatinine clearance ranges from 45 to 79 mL/min, monitor for myelosuppression, renal and GI toxicity. NSAIDs with short elimination half-lives (e.g., diclofenac, indomethacin) should be avoided for a period of two days before, the day of, and two days following administration of pemetrexed. In the absence of data regarding potential interaction between pemetrexed and NSAIDs with longer half-lives (e.g., meloxicam, nabumetone), patients taking these NSAIDs should interrupt dosing for at least five days before, the day of, and two days following pemetrexed administration. |
| Rifampin | |
| Clinical Impact: | Co-administration of Flexib with rifampin 600 mg daily, a potent inducer of hepatic metabolism, produced an approximate 50% decrease in Flexib plasma concentrations. |
| Intervention: | A starting daily dose of 25 mg of Flexib should be considered for the treatment of osteoarthritis when Flexib is co-administered with potent inducers of hepatic metabolism such as rifampin. |
| Theophylline | |
| Clinical Impact: | Flexib 12.5, 25, and 50 mg administered once daily for 7 days increased plasma theophylline concentrations (AUC(0-∞)) by 38 to 60% in healthy subjects administered a single 300-mg dose of theophylline. |
| Intervention: | Adequate monitoring of theophylline plasma concentrations should be considered when therapy with Flexib is initiated or changed in patients receiving theophylline. These data suggest that Flexib may produce a modest inhibition of cytochrome P450 (CYP) 1A2. Therefore, there is a potential for an interaction with other drugs that are metabolized by CYP 1A2 (e.g., amitriptyline, tacrine, and zileuton). |
Cimetidine: Co-administration with high doses of cimetidine [800 mg twice daily] has no significant effect on the pharmacokinetics of Flexib. The small changes in pharmacokinetics are not clinically significant and no dose adjustment is necessary.
Furosemide: Clinical studies, as well as post-marketing observations, have shown that NSAIDs can reduce the natriuretic effect of furosemide and thiazides in some patients. This response has been attributed to inhibition of renal prostaglandin synthesis.
Ketoconazole: Ketoconazole 400 mg daily did not have any clinically important effect on the pharmacokinetics of Flexib.
Oral Contraceptives
Prednisone/prednisolone: Flexib did not have any clinically important effect on the pharmacokinetics of prednisolone or prednisone.
See also:
What are the possible side effects of Flexib?
Osteoarthritis
Approximately 3600 patients with osteoarthritis were treated with Flexib; approximately 1400 patients received Flexib for 6 months or longer and approximately 800 patients for one year or longer. The following table of adverse experiences lists all adverse events, regardless of causality, occurring in at least 2% of patients receiving Flexib in nine controlled studies of 6-week to 6-month duration conducted in patients with OA at the therapeutically recommended doses (12.5 and 25 mg), which included a placebo and/or positive control group.
Clinical Adverse Experiences occurring in ≥ 2.0% of Patients Treated with Flexib in OA Clinical Trials
| Placebo (N = 783) | Flexib 12.5 or 25 mg daily (N = 2829) | Ibuprofen 2400 mg daily (N = 847) | Diclofenac 150 mg daily (N = 498) | |
| Body As A Whole/Site Unspecified | ||||
| Abdominal Pain | 4.1 | 3.4 | 4.6 | 5.8 |
| Asthenia/Fatigue | 1.0 | 2.2 | 2.0 | 2.6 |
| Dizziness | 2.2 | 3.0 | 2.7 | 3.4 |
| Influenza-Like Disease | 3.1 | 2.9 | 1.5 | 3.2 |
| Lower Extremity Edema | 1.1 | 3.7 | 3.8 | 3.4 |
| Upper Respiratory Infection | 7.8 | 8.5 | 5.8 | 8.2 |
| Cardiovascular System | ||||
| Hypertension | 1.3 | 3.5 | 3.0 | 1.6 |
| Digestive System | ||||
| Diarrhea | 6.8 | 6.5 | 7.1 | 10.6 |
| Dyspepsia | 2.7 | 3.5 | 4.7 | 4.0 |
| Epigastric Discomfort | 2.8 | 3.8 | 9.2 | 5.4 |
| Heartburn | 3.6 | 4.2 | 5.2 | 4.6 |
| Nausea | 2.9 | 5.2 | 7.1 | 7.4 |
| Eyes, Ears, Nose, And Throat | ||||
| Sinusitis | 2.0 | 2.7 | 1.8 | 2.4 |
| Musculoskeletal System | ||||
| Back Pain | 1.9 | 2.5 | 1.4 | 2.8 |
| Nervous System | ||||
| Headache | 7.5 | 4.7 22 | 6.1 | 8.0 |
| Respiratory System | ||||
| Bronchitis | 0.8 | 2.0 | 1.4 | 3.2 |
| Urogenital System | ||||
| Urinary Tract Infection | 2.7 | 2.8 | 2.5 | 3.6 |
In the OA studies, the following spontaneous adverse events occurred in > 0.1% to 1.9% of patients treated with Flexib regardless of causality:
Body as a Whole: abdominal distension, abdominal tenderness, abscess, chest pain, chills, contusion, cyst, diaphragmatic hernia, fever, fluid retention, flushing, fungal infection, infection, laceration, pain, pelvic pain, peripheral edema, postoperative pain, syncope, trauma, upper extremity edema, viral syndrome.
Cardiovascular System: angina pectoris, atrial fibrillation, bradycardia, hematoma, irregular heartbeat, palpitation, premature ventricular contraction, tachycardia, venous insufficiency.
Digestive System: acid reflux, aphthous stomatitis, constipation, dental caries, dental pain, digestive gas symptoms, dry mouth, duodenal disorder, dysgeusia, esophagitis, flatulence, gastric disorder, gastritis, gastroenteritis, hematochezia, hemorrhoids, infectious gastroenteritis, oral infection, oral lesion, oral ulcer, vomiting.
Eyes, Ears, Nose, and Throat: allergic rhinitis, blurred vision, cerumen impaction, conjunctivitis, dry throat, epistaxis, laryngitis, nasal congestion, nasal secretion, ophthalmic injection, otic pain, otitis, otitis media, pharyngitis, tinnitus, tonsillitis.
Immune System: allergy, hypersensitivity, insect bite reaction.
Metabolism and Nutrition: appetite change, hypercholesterolemia, weight gain.
Musculoskeletal System: ankle sprain, arm pain, arthralgia, back strain, bursitis, cartilage trauma, joint swelling, muscular cramp, muscular disorder, muscular weakness, musculoskeletal pain, musculoskeletal stiffness, myalgia, osteoarthritis, tendinitis, traumatic arthropathy, wrist fracture.
Nervous System: hypesthesia, insomnia, median nerve neuropathy, migraine, muscular spasm, paresthesia, sciatica, somnolence, vertigo.
Psychiatric: anxiety, depression, mental acuity decreased.
Respiratory System: asthma, cough, dyspnea, pneumonia, pulmonary congestion, respiratory infection.
Skin and Skin Appendages: abrasion, alopecia, atopic dermatitis, basal cell carcinoma, blister, cellulitis, contact dermatitis, herpes simplex, herpes zoster, nail unit disorder, perspiration, pruritus, rash, skin erythema, urticaria, xerosis.
Urogenital System: breast mass, cystitis, dysuria, menopausal symptoms, menstrual disorder, nocturia, urinary retention, vaginitis.
The following serious adverse events have been reported rarely (estimated < 0.1%) in patients taking Flexib, regardless of causality. Cases reported only in the post-marketing experience are indicated in italics.
Cardiovascular: cerebrovascular accident, congestive heart failure, deep venous thrombosis, hypertensive crisis, myocardial infarction, pulmonary edema, pulmonary embolism, transient ischemic attack, unstable angina.
Gastrointestinal: cholecystitis, colitis, colonic malignant neoplasm, duodenal perforation, duodenal ulcer, esophageal ulcer, gastric perforation, gastric ulcer, gastrointestinal bleeding, hepatic failure, hepatitis, intestinal obstruction, jaundice, pancreatitis.
Hemic and lymphatic: agranulocytosis, aplastic anemia, leukopenia, lymphoma, pancytopenia, thrombocytopenia.
Immune System: anaphylactic/anaphylactoid reaction, angioedema, bronchospasm, hypersensitivity vasculitis.
Metabolism and nutrition: hyponatremia.
Nervous System: aseptic meningitis, epilepsy aggravated.
Psychiatric: confusion, hallucinations.
Skin and Skin Appendages: photosensitivity reactions, severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis.
Urogenital System: acute renal failure, breast malignant neoplasm, hyperkalemia, interstitial nephritis, prostatic malignant neoplasm, urolithiasis, worsening chronic renal failure.
In 1-year controlled clinical trials and in extension studies for up to 86 weeks (approximately 800 patients treated with Flexib for one year or longer), the adverse experience profile was qualitatively similar to that observed in studies of shorter duration.
Rheumatoid Arthritis
Approximately 1,100 patients were treated with Flexib in the Phase III rheumatoid arthritis efficacy studies. These studies included extensions of up to 1 year. The adverse experience profile was generally similar to that reported in the osteoarthritis studies. In studies of at least three months, the incidence of hypertension in RA patients receiving the 25 mg once daily dose of Flexib was 10.0% and the incidence of hypertension in patients receiving naproxen 500 mg twice daily was 4.7%.
Analgesia, Including Primary Dysmenorrhea
Approximately one thousand patients were treated with Flexib in analgesia studies. All patients in post-dental surgery pain studies received only a single dose of study medication. Patients in primary dysmenorrhea studies may have taken up to 3 daily doses of Flexib, and those in the post-orthopedic surgery pain study were prescribed 5 daily doses of Flexib.
The adverse experience profile in the analgesia studies was generally similar to those reported in the osteoarthritis studies. The following additional adverse experience, which occurred at an incidence of at least 2% of patients treated with Flexib, was observed in the post-dental pain surgery studies: post-dental extraction alveolitis (dry socket).
Migraine With Or Without Aura
Approximately 750 patients were treated with a single dose of Flexib 25 mg or 50 mg in two single-attack migraine studies. Approximately 460 patients in the 3-month extension phase of one study treated up to 8 (average 3) migraine attacks per month. In single attack studies, the following adverse events were more frequent in the Flexib treatment groups (25 mg and 50 mg) compared to the placebo group, and occurred at an incidence of at least 2% of patients treated: dizziness, nausea, somnolence and dyspepsia. In the 3-month extension phase of one study, the following adverse events occurred at an incidence of at least 2% of patients treated in the Flexib treatment groups (25 mg and 50 mg): dizziness, dry mouth, nausea, and vomiting.
Clinical Studies In OA And RA With Flexib 50 mg (Twice the highest dose recommended for chronic use)
In OA and RA clinical trials which contained Flexib 12.5 or 25 mg as well as Flexib 50 mg, Flexib 50 mg QD was associated with a higher incidence of gastrointestinal symptoms (abdominal pain, epigastric pain, heartburn, nausea and vomiting), lower extremity edema, hypertension, serious* adverse experiences and discontinuation due to clinical adverse experiences compared to the recommended chronic doses of 12.5 and 25 mg.
Pauciarticular And Polyarticular Course Juvenile Rheumatoid Arthritis
In a 12-week study, 209 JRA patients, ≥ 2 years to ≤ 17 years of age, were treated with Flexib; 109 and 100 patients were treated with lower-dose Flexib and higher-dose Flexib, respectively. In a 52-week open-label extension, 160 JRA patients, ≥ 2 years to ≤ 17 years of age, were treated with higher-dose Flexib for up to 15 months. No new adverse experiences were identified other than a single case of pseudoporphyria (a photo-induced blistering reaction), an adverse event that has been seen in patients with JRA treated with non-selective NSAIDs. In this 12-week study, the most common adverse experiences (at 0.6 mg/kg dose) were upper abdominal pain, nasopharyngitis, diarrhea, upper respiratory tract infection, abdominal pain, headache and rhinitis. Rash was also reported.