Ibuprofen

Active Ingredient & Mechanism of Action

• Active Ingredient: Ibuprofen.
• Mechanism: Ibuprofen works by non-selectively inhibiting the cyclooxygenase (COX) enzymes: COX-1 and COX-2:
  1. Inhibition of Prostaglandin Synthesis: By blocking COX enzymes, it stops the conversion of arachidonic acid into prostaglandins—lipid compounds that mediate inflammation, swelling, fever, and pain signaling.
  2. Peripheral Action: Unlike acetaminophen, ibuprofen directly reduces localized tissue inflammation and swelling at the site of injury or disease.

Dosage Forms & Available Strengths

• Over-the-Counter (OTC) Oral Formulations: 200 mg tablets, caplets, or softgel liquid capsules.
• Prescription Oral Formulations: 400 mg, 600 mg, and 800 mg tablets.
• Pediatric Suspensions & Drops: 100 mg / 5 mL liquid suspensions or 50 mg / 1.25 mL infant drops.
• Topical Formulations: Gels or creams (typically 5%) for localized joint or muscle pain.
• Intravenous (IV) Infusion: Formulations used in hospital settings for acute pain or fever management.

Clinical Indications

• Mild-to-Moderate Pain: Relief of headaches, dental pain, muscle aches, backaches, dysmenorrhea (menstrual cramps), and postoperative discomfort.
• Fever Reduction: Lowering elevated body temperature in adults and children.
• Inflammatory Conditions: Symptomatic management of rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, tendonitis, and acute gout flares.

Key Pharmacokinetics

• Absorption: Rapidly absorbed from the gastrointestinal tract, reaching peak plasma concentrations within 1 to 2 hours (faster with softgel liquid capsules).
• Protein Binding & Distribution: High plasma protein binding ($> 99\%$, primarily to albumin). Distributes well into synovial fluid (joint spaces).
• Metabolism & Elimination: Extensively metabolized by the liver via CYP2C9 into inactive metabolites. Elimination half-life is short, approximately 1.8 to 2 hours. It is excreted predominantly through the kidneys in urine.

Administration Guidelines & Dosing Limits

• Food Requirement: Should ideally be taken with food, milk, or an antacid to minimize gastrointestinal irritation and stomach upset.
• OTC Adult Dosing: 200 mg to 400 mg every 4 to 6 hours as needed.
• Maximum Daily Dose Limits:
  • OTC Maximum Limit: 1,200 mg in 24 hours unless directed otherwise by a physician.
  • Prescription Maximum Limit: 3,200 mg in 24 hours (typically split into 600 mg or 800 mg doses taken 3 to 4 times daily under medical supervision).
• Pediatric Dosing: Weight-based dosing at 5 to 10 mg/kg per dose every 6 to 8 hours (maximum 40 mg/kg per day).

Safety Profile & Critical Warnings

• Boxed Warnings (Black Box Warnings):
  1. Cardiovascular Risk: NSAIDs increase the risk of serious cardiovascular thrombotic events, including myocardial infarction (heart attack) and stroke. Risk increases with higher doses, prolonged use, or pre-existing heart disease.
  2. Gastrointestinal Risk: Causes an increased risk of severe GI adverse events, including bleeding, ulceration, and perforation of the stomach or intestines, which can occur without warning.
• Renal Risk (Kidney Toxicity): Long-term use or dehydration can impair renal blood flow, leading to fluid retention, elevated blood pressure, and acute kidney injury (renal papillary necrosis).
• Common Side Effects: Dyspepsia (heartburn), abdominal pain, nausea, diarrhea, dizziness, and mild headache.
• Pregnancy Warning: Contraindicated starting at 20 weeks of gestation (late pregnancy) because it can cause premature closure of the fetal ductus arteriosus and lower amniotic fluid levels (oligohydramnios).
• Key Drug Interactions:
  • Aspirin / Blood Thinners (e.g., Warfarin, DOACs): Concurrent use dramatically increases gastrointestinal and systemic bleeding risks.
  • Antihypertensives (ACE Inhibitors, ARBs, Diuretics): Ibuprofen can diminish the blood-pressure-lowering effectiveness of these drugs and increase kidney toxicity risks.
  • Steroids (Corticosteroids) & SSRIs: Co-administration elevates gastrointestinal ulceration and bleeding risks.

Note: Ibuprofen is an over-the-counter and prescription NSAID. Dosage duration, maximum daily limits, and individual cardiovascular or gastrointestinal risk factors should be evaluated with a qualified healthcare provider or pharmacist.