Chloroquine

Chloroquine phosphate is a well-established medication primarily indicated for the prophylaxis and treatment of acute attacks of malaria due to susceptible strains of plasmodia. It belongs to the 4-aminoquinoline class of compounds and has been a cornerstone in antimalarial therapy for decades. Beyond its antiparasitic applications, chloroquine exhibits significant immunomodulatory properties, leading to its use in the management of certain autoimmune conditions such as rheumatoid arthritis and lupus erythematosus. Its mechanism involves raising intravesicular pH within parasitic and host cells, which interferes with critical processes like hemoglobin degradation and antigen presentation.

Features

• Active ingredient: Chloroquine phosphate
• Available in 250 mg and 500 mg oral tablets
• Also supplied as an injectable solution for hospital use
• Long half-life allowing for weekly dosing in prophylaxis
• Well-characterized pharmacokinetic profile
• Manufactured under strict pharmaceutical quality standards

Benefits

• Provides effective prophylaxis against malaria in endemic regions
• Rapidly terminates acute malarial febrile attacks
• Reduces symptoms and progression in autoimmune disorders
• Cost-effective compared to many newer antimalarials
• Established safety profile with decades of clinical use
• Convenient dosing regimen for both treatment and prevention

Common use

Chloroquine is primarily prescribed for the prevention and treatment of malaria caused by Plasmodium vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. It is particularly valuable for travelers to malaria-endemic areas who require chemoprophylaxis. In rheumatology, chloroquine is used as a disease-modifying antirheumatic drug (DMARD) for managing rheumatoid arthritis and systemic lupus erythematosus. Off-label applications include treatment of Q fever, porphyria cutanea tarda, and certain photodermatoses, though these uses require careful medical supervision.

Dosage and direction

Malaria Prophylaxis (Adults): 500 mg (300 mg base) orally once weekly, starting 1-2 weeks before exposure and continuing for 4 weeks after leaving endemic area.

Acute Malaria Treatment (Adults): Initial dose of 1 g (600 mg base) followed by 500 mg (300 mg base) at 6, 24, and 48 hours.

Rheumatoid Arthritis (Adults): 250-500 mg (150-300 mg base) daily administered with food or milk.

Dosage must be adjusted for pediatric patients based on body weight. All dosing should be precisely calculated using the base content rather than salt weight. Patients should be instructed to take the medication with food or a full glass of milk to minimize gastrointestinal discomfort.

Precautions

Regular ophthalmologic examinations (including visual acuity, slit-lamp, funduscopic, and visual field testing) are mandatory every 6-12 months during long-term therapy due to risk of irreversible retinopathy. Complete blood counts should be monitored periodically as chloroquine may cause bone marrow suppression. Hepatic function should be assessed regularly, particularly in patients with pre-existing liver conditions. Use with caution in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to potential hemolytic risk. Patients with psoriasis may experience exacerbation of their condition. Neuromuscular weakness may occur in patients with myasthenia gravis.

Contraindications

Hypersensitivity to chloroquine or other 4-aminoquinoline compounds. Pre-existing retinal or visual field changes of any etiology. Concurrent administration with other drugs known to cause retinal toxicity. Patients with porphyria. History of epilepsy (may lower seizure threshold). Known hypersensitivity to hydroxychloroquine. Use in children under 6 years except for malaria treatment when benefits outweigh risks.

Possible side effect

Common reactions include headache, dizziness, nausea, vomiting, diarrhea, abdominal cramps, and pruritus (particularly in black patients). Ocular effects may include reversible corneal deposits, blurred vision, and photophobia. Serious adverse effects include irreversible retinopathy with visual field defects, ototoxicity (tinnitus, hearing loss), cardiomyopathy, skeletal muscle myopathy, blood dyscrasias (aplastic anemia, agranulocytosis, thrombocytopenia), and severe hypoglycemia. Neuropsychiatric effects such as psychosis, depression, and anxiety may occur. Skin manifestations include bleaching of hair, skin rash, and photosensitivity reactions.

Drug interaction

Chloroquine may potentiate the effects of digoxin and cyclosporine through unknown mechanisms. Concurrent use with hepatotoxic drugs increases risk of liver damage. Antacids and kaolin may reduce absorption. Cimetidine may increase chloroquine levels by inhibiting metabolism. May increase risk of convulsions when used with other epileptogenic drugs. May enhance effects of insulin and oral hypoglycemics. Concomitant use with mefloquine may increase risk of convulsions. Ampicillin absorption may be reduced when taken with chloroquine.

Missed dose

For weekly malaria prophylaxis: Take the missed dose as soon as remembered, then resume the regular weekly schedule. Do not double the dose. For daily treatment regimens: Take the missed dose as soon as remembered unless it is almost time for the next dose, in which case skip the missed dose and resume the regular schedule. Do not take extra medication to make up for a missed dose. Patients should maintain a medication diary to track adherence, particularly for prophylactic regimens.

Overdose

Chloroquine overdose is extremely dangerous and potentially fatal, with as little as 2-3 g potentially causing death in adults. Symptoms include headache, drowsiness, visual disturbances, cardiovascular collapse, convulsions, and sudden respiratory and cardiac arrest. Hypokalemia is a characteristic finding. Management requires immediate gastric lavage (within 1 hour) and activated charcoal. Respiratory support and cardiovascular monitoring are essential. Intravenous diazepam may be administered for convulsions. Potassium supplementation should be provided cautiously with continuous ECG monitoring. Emergency medical attention is immediately required for suspected overdose.

Storage

Store at controlled room temperature (20-25°C or 68-77°F) in the original container. Protect from light and moisture. Keep tightly closed and out of reach of children. Do not store in bathroom or other areas with high humidity. Discard any medication that has expired or shows signs of deterioration. Do not flush medications down the toilet or pour into drain unless instructed to do so.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Chloroquine is a prescription medication that should only be used under the supervision of a qualified healthcare professional. The prescribing physician should be consulted for specific medical advice, diagnosis, and treatment. Always follow the dosage instructions provided by your healthcare provider. Not all possible uses, precautions, side effects, or interactions are listed here.

Reviews

Clinical studies have demonstrated chloroquine’s efficacy in malaria prophylaxis with protection rates exceeding 90% in areas with susceptible strains. In rheumatoid arthritis, multiple randomized controlled trials show significant improvement in joint swelling, tenderness, and morning stiffness. However, increasing resistance in P. falciparum has limited its utility in many regions. Ophthalmologic monitoring remains crucial for long-term users, with studies indicating retinopathy risk of approximately 1% after 5-7 years of use. Patient satisfaction surveys indicate good tolerability when properly dosed, though gastrointestinal complaints are common initially.