Generic Name

Hydroxychloroquine Sulfate

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Classification

FDA Approved Indications

• Lupus erythematosus
• Rheumatoid arthritis
• Malaria

Mechanism of Action

Hydroxychloroquine interferes with lysosomal activity and antigen presentation, which modulates immune responses. Its exact mechanism in malaria involves inhibiting parasite growth by interfering with parasite’s digestive vacuole function.

Dosage and Administration

Adult: For rheumatoid arthritis or lupus, typically 200-400 mg twice weekly or daily, adjusted based on response and tolerance.

Pediatric: Dosing based on weight; typically 6.5 mg/kg/day divided into one or two doses, not exceeding 400 mg/day.

Geriatric: Use with caution; start at the lower end of dosing due to potential cardiotoxicity and other comorbidities.

Renal Impairment: Adjust dose; monitor renal function, particularly in chronic use.

Hepatic Impairment: Use with caution; no specific dosage adjustment, but monitor liver function.

Pharmacokinetics

Absorption: Well-absorbed orally with approximately 70-80% bioavailability.

Distribution: Widely distributed into tissues, especially liver, spleen, and eyes.

Metabolism: Metabolized minimally; some oxidative metabolism occurs in the liver.

Excretion: Excreted primarily via the urine; a small amount is excreted in feces.

Half Life: Approximate half-life is 40-50 days due to extensive tissue binding.

Contraindications

• Hypersensitivity to hydroxychloroquine or related quinines
• Retinal or visual field changes from previous hydroxychloroquine use
• History of porphyria

Precautions

• Regular ophthalmologic examinations recommended
• Caution in hepatic or renal impairment
• Use during pregnancy only if potential benefit justifies potential risk
• Lactation: Considered compatible, but monitor infant for adverse effects

Adverse Reactions - Common

• Gastrointestinal disturbances (Common)
• Headache (Common)
• Dizziness (Common)

Adverse Reactions - Serious

• Retinal toxicity leading to irreversible vision loss (Rare; but risk increases with duration and dose)
• Cardiomyopathy (Rare)
• Myopathy (Rare)

Drug-Drug Interactions

• Amiodarone (increased risk of cardiotoxicity)
• Digoxin (altered levels)
• Mefloquine (increased risk of neuropsychiatric effects)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Report any visual changes immediately
• Take medication exactly as prescribed
• Attend scheduled eye examinations
• Inform about possible gastrointestinal side effects

Special Considerations

Black Box Warnings:

• Retinal toxicity; irreversible damage with long-term use

Genetic Factors: Genetic variations may influence metabolism and risk of adverse effects, though not routinely tested

Lab Test Interference: May interfere with certain diagnostic tests like glucose testing

Overdose Management

Signs/Symptoms: Vomiting, convulsions, hypoglycemia, cardiotoxicity, visual disturbances

Treatment: Supportive care, activated charcoal if recent ingestion, cardiac monitoring, intravenous lipid emulsion in severe cardiotoxicity

Storage and Handling

Storage: Store at room temperature, 15-30°C, away from light and moisture

Stability: Stable under proper storage conditions for the duration of shelf life