Usage
Chloroquine is prescribed for the prevention and treatment of malaria caused by Plasmodium vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. It is also used for the treatment of extraintestinal amebiasis and for the symptomatic treatment of discoid and systemic lupus erythematosus and rheumatoid arthritis. It is classified as an antimalarial and anti-inflammatory drug.
Chloroquine’s mechanism of action involves inhibiting heme polymerase, which converts heme (toxic to the parasite) into hemozoin (non-toxic). By blocking this conversion, toxic heme accumulates, leading to parasite death.
Alternate Names
- International/Regional Variations: Chloroquine phosphate, Chloroquine sulfate
- Brand Names: Aralen, Avloclor, Malarivon
How It Works
Pharmacodynamics: Chloroquine concentrates within the parasite’s food vacuole, where it interferes with the detoxification of heme into hemozoin. The accumulation of heme within the parasite is toxic, leading to its demise. Chloroquine also has anti-inflammatory effects, though the exact mechanism is not fully understood. It is believed to interfere with antigen processing and presentation, modulate cytokine production, and inhibit phospholipase A2.
Pharmacokinetics:
- Absorption: Well-absorbed orally.
- Distribution: Widely distributed throughout the body, with high concentrations in the liver, kidneys, lungs, spleen, and erythrocytes. Crosses the placental barrier and is found in breast milk.
- Metabolism: Partially metabolized in the liver to desethylchloroquine, an active metabolite.
- Elimination: Primarily renal excretion, with a small amount excreted in feces.
Dosage
Standard Dosage
Adults:
- Malaria treatment: 1000 mg (600 mg base) initially, followed by 500 mg (300 mg base) 6-8 hours later, then 500 mg (300 mg base) daily for 2 more days.
- Malaria prophylaxis: 500 mg (300 mg base) once weekly, starting 2 weeks before travel and continuing for 4 weeks after leaving the malarious area.
- Amebiasis: 1000 mg (600 mg base) daily for 2 days, then 500 mg (300 mg base) daily for 2-3 weeks.
- Lupus erythematosus/Rheumatoid Arthritis: 250 mg daily.
Children:
- Malaria treatment: 10 mg/kg (base) initially (max 600 mg base), then 5 mg/kg (base) at 6, 24, and 48 hours (max 300 mg base per dose).
- Malaria prophylaxis: 5 mg/kg (base) once weekly (max 300 mg base), starting 2 weeks before travel and continuing for 4 weeks after leaving the malarious area.
Special Cases:
- Elderly Patients: Renal function should be monitored; dose adjustment may be needed.
- Patients with Renal Impairment: Reduce dose for creatinine clearance <10 mL/minute.
- Patients with Hepatic Dysfunction: Caution is advised; dose adjustment may be needed.
- Patients with Comorbid Conditions: Careful monitoring for drug interactions.
Clinical Use Cases
Chloroquine is not indicated for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations like status epilepticus or cardiac arrest.
Dosage Adjustments
Dose adjustments may be necessary for patients with renal or hepatic impairment, or those with other comorbid conditions. Consult current clinical guidelines for specific recommendations.
Side Effects
Common Side Effects
Nausea, vomiting, diarrhea, abdominal cramps, headache, dizziness, vision changes (blurring), changes in hair/skin color.
Rare but Serious Side Effects
Ototoxicity, retinopathy, seizures, blood dyscrasias (e.g., agranulocytosis, thrombocytopenia), cardiomyopathy, hypoglycemia, neuropsychiatric effects (e.g., anxiety, depression, hallucinations).
Long-Term Effects
Irreversible retinopathy, ototoxicity, neuromuscular toxicity.
Adverse Drug Reactions (ADR)
Severe hypoglycemia, cardiotoxicity, neuropsychiatric reactions.
Contraindications
Hypersensitivity to chloroquine, pre-existing retinal or visual field changes (relative contraindication for long-term use), psoriasis (may exacerbate), porphyria.
Drug Interactions
Chloroquine may interact with several medications, including:
- Cimetidine: May increase chloroquine levels.
- Antacids: May decrease chloroquine absorption.
- Digoxin: May increase digoxin levels.
- Mefloquine: Increased risk of seizures.
- Other antimalarials: Avoid concurrent use unless specifically indicated.
Pregnancy and Breastfeeding
Chloroquine can be used during pregnancy if the benefits outweigh the risks, especially for malaria treatment/prophylaxis. However, it should be avoided for chronic conditions like lupus or rheumatoid arthritis if possible.
Small amounts of chloroquine are present in breast milk. Weekly chloroquine for malaria prophylaxis is generally considered safe during breastfeeding, but infants require separate malaria prophylaxis. For daily use, alternative medications might be preferred, especially for newborns or preterm infants.
Drug Profile Summary
- Mechanism of Action: Inhibits heme polymerase in the malaria parasite, leading to heme accumulation and parasite death. Also has anti-inflammatory properties.
- Side Effects: Nausea, vomiting, diarrhea, headache, dizziness, vision changes, hair/skin color changes (common); retinopathy, ototoxicity, seizures, blood dyscrasias, cardiomyopathy, hypoglycemia, neuropsychiatric effects (serious).
- Contraindications: Hypersensitivity, pre-existing retinal/visual field changes, psoriasis, porphyria.
- Drug Interactions: Cimetidine, antacids, digoxin, mefloquine, other antimalarials.
- Pregnancy & Breastfeeding: Can be used in pregnancy if benefits outweigh risks; small amounts in breast milk, infant requires separate malaria prophylaxis.
- Dosage: See detailed dosage section above.
- Monitoring Parameters: Visual acuity, complete blood count, liver function tests, renal function tests, ECG (for long-term use).
Popular Combinations
Chloroquine is often used in combination with primaquine for the radical cure of P. vivax and P. ovale infections (after delivery in pregnant women).
Precautions
- Baseline ophthalmological exam recommended for long-term use.
- Monitor for signs of ototoxicity, blood dyscrasias, and cardiomyopathy.
- Caution in patients with G6PD deficiency.
- Avoid in patients with psoriasis or porphyria.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chloroquine?
A: Please refer to the detailed Dosage section above, as it varies considerably based on indication, age, and patient-specific factors.
Q2: Is Chloroquine safe in pregnancy?
A: It can be used if benefits outweigh risks, especially for malaria. Avoid for chronic conditions like lupus if possible.
Q3: Can I breastfeed while taking Chloroquine?
A: Small amounts are present in breast milk. Weekly use is generally safe, but infants need separate malaria prophylaxis. Alternatives may be preferred for daily use.
Q4: What are the serious side effects of Chloroquine?
A: Retinopathy, ototoxicity, seizures, blood dyscrasias, cardiomyopathy, hypoglycemia, neuropsychiatric effects.
Q5: What are the common drug interactions with Chloroquine?
A: Cimetidine, antacids, digoxin, mefloquine, other antimalarials.
Q6: What should be monitored in patients on long-term Chloroquine?
A: Visual acuity, complete blood count, liver and renal function tests, ECG.
Q7: What is the mechanism of action of Chloroquine in malaria?
A: It inhibits heme polymerase, preventing heme detoxification and causing toxic heme buildup in the parasite.
Q8: What are the contraindications for Chloroquine?
A: Hypersensitivity, pre-existing retinal/visual field changes, psoriasis, porphyria.
Q9: What is the role of Chloroquine in amebiasis?
A: It is used for the treatment of extraintestinal amebiasis. It is not effective against intraluminal amebiasis.
