The 436 pill most commonly refers to prescription Naproxen 500 mg, manufactured by ScieGen Pharmaceuticals, Inc. (imprinted with SG and 436). Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) with potent analgesic, anti-inflammatory, and antipyretic properties. It is not a controlled substance.
Pill Identification & Physical Characteristics
Property – Primary Identification (Naproxen 500 mg) – Secondary Identification (Allopurinol 300 mg)
- Active Ingredient – Naproxen (500 mg) – Allopurinol (300 mg)
- Imprint –
SG(with break-line) on one side;436on reverse –436with a raised hexagon symbol - Shape & Color – Oblong / Capsule-shaped; Light Yellow – Round; White
- Drug Class – Nonsteroidal Anti-inflammatory Drug (NSAID) – Xanthine Oxidase Inhibitor
- Manufacturer – ScieGen Pharmaceuticals, Inc. – Accord Healthcare / Vintage
Mechanism of Action
Naproxen is a non-selective inhibitor of the cyclooxygenase enzymes COX-1 and COX-2:
- Prostaglandin Synthesis Inhibition: Cyclooxygenase catalyzes the conversion of arachidonic acid to prostaglandin , the precursor to pro-inflammatory prostaglandins, prostacyclin, and thromboxane . By reversibly inhibiting both COX isoenzymes, naproxen reduces peripheral and central prostaglandin production.
- Analgesic and Anti-inflammatory Effects: Decreased prostaglandin concentrations reduce the sensitivity of nociceptive nerve endings to chemical mediators (such as bradykinin) and suppress local inflammatory responses, tissue edema, and joint stiffness.
- Antipyretic Effect: In the preoptic area of the anterior hypothalamus, naproxen inhibits prostaglandin synthesis, resetting the hypothalamic thermostat to lower fever.
Indications & Dosage
Approved Indications
- Chronic Inflammatory Arthritis: Rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis.
- Acute Musculoskeletal Disorders: Tendonitis, bursitis, and acute sprains/strains.
- Acute Gout: Management of acute gouty arthritis flare-ups.
- Acute Pain & Dysmenorrhea: Mild-to-moderate pain and primary menstrual cramping.
General Adult Dosing (Naproxen 500 mg)
- Arthritis / Ankylosing Spondylitis: Typically 250 mg to 500 mg orally twice daily (morning and evening), up to a maximum of 1,500 mg/day for limited durations during acute exacerbations.
- Acute Pain, Dysmenorrhea, Tendonitis: Starting dose of 500 mg, followed by 250 mg every 6 to 8 hours or 500 mg every 12 hours as needed (maximum daily dose: 1,250 mg).
- Acute Gout: Recommended initial dose of 750 mg, followed by 250 mg every 8 hours until the acute attack subsides.
- Administration: Swallow whole with a full glass of water. Taking naproxen with food, milk, or an antacid is recommended to reduce gastrointestinal irritation.
Side Effects
Common Adverse Reactions
- Dyspepsia (heartburn), nausea, and abdominal pain
- Constipation, diarrhea, or flatulence
- Headache, dizziness, and lightheadedness
- Peripheral edema (fluid retention)
- Tinnitus (ringing in the ears)
- Mild skin rash or pruritus
Severe & Emergent Reactions
- Gastrointestinal Ulceration & Hemorrhage: Hematemesis (vomiting blood), melena (black, tarry stools), or gastric perforation.
- Cardiovascular Events: Myocardial infarction, stroke, new-onset hypertension, or worsening congestive heart failure.
- Nephrotoxicity & Acute Kidney Injury: Interstitial nephritis, renal papillary necrosis, or elevated serum creatinine (especially in dehydrated or hypovolemic patients).
- Severe Cutaneous Reactions: Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).
- Hepatotoxicity: Severe elevations in liver transaminases (ALT/AST) or rare hepatic failure.
Precautions & Drug Interactions
- Anticoagulants and Antiplatelets: Co-administration with warfarin, direct oral anticoagulants (DOACs), clopidogrel, or aspirin significantly increases the risk of major gastrointestinal bleeding.
- Other NSAIDs and Corticosteroids: Concurrent use with other NSAIDs (e.g., ibuprofen, meloxicam) or systemic oral corticosteroids (e.g., prednisone) amplifies ulceration and perforation hazards without increasing therapeutic efficacy.
- Antihypertensive Agents (ACE inhibitors, ARBs, Diuretics): NSAIDs attenuate the blood pressure-lowering effects of ACE inhibitors and ARBs and increase the risk of acute renal deterioration (the “triple whammy” when combined with diuretics).
- Lithium and Methotrexate: Naproxen decreases the renal clearance of lithium and methotrexate, leading to elevated plasma levels and potential toxicity.
- Pregnancy Warning: NSAID use is contraindicated at 20 weeks of gestation and beyond due to risks of fetal renal dysfunction resulting in oligohydramnios, and at 30 weeks and beyond due to premature closure of the fetal ductus arteriosus.
Black Box Warnings
FDA Boxed Warnings for NSAIDs:
- Cardiovascular Thrombotic Events: Nonsteroidal anti-inflammatory drugs cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and increases with duration of use. Naproxen is strictly contraindicated in the setting of coronary artery bypass graft (CABG) surgery.
- Gastrointestinal Risk: NSAIDs cause an increased risk of serious gastrointestinal adverse events, including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms. Elderly patients and those with a prior history of peptic ulcer disease or GI bleeding are at greater risk.