Plaquenil® (Hydroxychloroquine Sulfate Tablets USP)

Product Information

• Name: Plaquenil®
• Active Ingredient: Hydroxychloroquine Sulfate
• Strength: 200 mg tablets (equivalent to 155 mg base)
• Manufacturer: Sanofi-aventis Canada Inc.

Therapeutic Classification

• Class: Anti-Inflammatory, Antimalarial, Aminoquinolines

Indications and Clinical Use

• Rheumatoid Arthritis (RA): For patients who have not responded satisfactorily to drugs with less potential for serious side effects.
• Systemic Lupus Erythematosus (SLE) and Discoid Lupus Erythematosus (DLE): Effective in controlling the disease.
• Malaria: Suppressive treatment and treatment of acute attacks due to P. vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum.

Contraindications

• Pre-existing retinopathy of the eye.
• Known hypersensitivity to 4-aminoquinoline compounds.
• Children below 6 years of age or weighing less than 35 kg.

Warnings and Precautions

• Retinopathy: Risk of irreversible retinal damage; regular ophthalmologic examinations required.
• Cardiovascular: Risk of cardiomyopathy and arrhythmias; monitor ECG and discontinue if signs develop.
• Hypoglycemia: Severe hypoglycemia risk; monitor blood glucose levels.
• Neuropsychiatric Effects: Risk of suicidal behavior and psychiatric symptoms.
• Musculoskeletal: Risk of muscle weakness; regular examination recommended.
• Hematologic: Periodic blood counts required due to the risk of bone marrow depression.
• Hepatic Impairment: Use with caution and consider dosage reduction.
• Renal Impairment: Use with caution and consider dosage reduction.
• Skin Reactions: Risk of severe skin reactions; monitor for symptoms.

Adverse Reactions

• Common: Nausea, vomiting, diarrhea, abdominal pain, headache, rash, pruritus.
• Serious: Retinopathy, cardiomyopathy, hypoglycemia, suicidal behavior, severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis).
• Other: Visual disturbances, dizziness, hair bleaching, alopecia, hearing loss, muscle weakness, and psychiatric disorders.

Drug Interactions

• QT Interval Prolongation: Avoid concomitant use with other QT-prolonging drugs.
• Hypoglycemic Drugs: May enhance effects; monitor and adjust dosage.
• Cyclosporine: Increased plasma levels; monitor closely.
• Antacids: May reduce absorption; observe a 4-hour interval between doses.
• Tamoxifen: Increased risk of retinal toxicity; avoid concomitant use.
• Other: Interactions with cimetidine, digoxin, aminoglycosides, and antiepileptic drugs.

Dosage and Administration

• Rheumatoid Arthritis:
  • Initial: 400-600 mg daily.
  • Maintenance: 200-400 mg daily.
• Lupus Erythematosus:
  • Initial: 400 mg once or twice daily.
  • Maintenance: 200-400 mg daily.
• Malaria:
  • Adult Dosage:
    • Prevention: 310 mg base once weekly, starting one week before entering a malaria-endemic area, during exposure, and for 4 weeks after leaving.
    • Treatment: Loading dose of 620 mg base, followed by 310 mg base at 6, 24, and 48 hours.
  • Pediatric Dosage:
    • Prevention: 5 mg base/kg once weekly (specific doses provided).
    • Treatment: Loading dose of 10 mg base/kg, followed by 5 mg base/kg at 6, 24, and 48 hours.
  • Advantage:
    • Long-term safety data for prophylaxis.
  • Disadvantage:
    • Most areas now report chloroquine resistance.

Symptoms and Treatment of Overdosage

• Symptoms: Headache, drowsiness, visual disturbances, cardiovascular collapse, hypokalemia, convulsions, arrhythmias, respiratory and cardiac arrest.
• Treatment: Immediate medical attention, gastric lavage, activated charcoal, symptomatic and supportive care, monitoring ECG and electrolytes, and administering diazepam if necessary.

Storage and Stability

• Store at room temperature (15°C - 30°C).
• Keep out of reach of children.