Common uses of Chloroquine
Chloroquine is primarily indicated for the prevention and treatment of malaria caused by chloroquine-sensitive Plasmodium species, most notably P. vivax, P. ovale, P. malariae, and some strains of P. falciparum where sensitivity persists. Because widespread resistance exists in many regions, particularly sub-Saharan Africa, Southeast Asia, and parts of South America, its use is geographically restricted based on up-to-date resistance maps from the CDC or WHO. It is also used to treat extraintestinal amebiasis caused by Entamoeba histolytica, typically in combination with a luminal agent to eradicate intestinal colonization.
Chloroquine is not the same as hydroxychloroquine. Hydroxychloroquine is often preferred for autoimmune conditions such as systemic lupus erythematosus and rheumatoid arthritis due to a more favorable safety profile. Chloroquine is generally not used for long-term autoimmune therapy in the U.S. and is not recommended for prevention or treatment of COVID-19; major guidelines advise against its use for viral infections outside of clinical trials.
Dosage and direction
Dosing of chloroquine varies by indication, patient weight, and the salt/base formulation. Many tablets contain chloroquine phosphate; 500 mg of chloroquine phosphate typically corresponds to approximately 300 mg of chloroquine base. Prescribers dose in mg/kg of base, so it is critical to follow a clinician’s instructions and the specific product label. Do not self-calculate or self-treat malaria; inappropriate dosing risks treatment failure, toxicity, and resistance.
Treatment of chloroquine-sensitive malaria in adults commonly follows a total dose of 25 mg base/kg over 3 days (for example, an initial dose followed by smaller doses at 6, 24, and 48 hours). For pediatric patients, weight-based dosing is essential, with maximum doses not exceeding adult totals. Because relapse prevention in P. vivax and P. ovale requires eradication of dormant liver forms, primaquine or tafenoquine may be prescribed after confirming G6PD status; do not attempt this without medical supervision.
Malaria prophylaxis with chloroquine (in areas with chloroquine-sensitive malaria only) is typically administered once weekly. Adults often receive the equivalent of 300 mg base weekly, starting 1–2 weeks before entering the endemic area, continuing weekly during exposure, and for 4 weeks after leaving. Children receive weight-based once-weekly doses (not exceeding the adult dose). Always verify destination-specific recommendations, as many travel regions require alternative agents due to resistance.
Administration tips: take chloroquine with food to reduce gastrointestinal upset. Avoid co-administration with antacids or kaolin-containing adsorbents, which can reduce absorption; if needed, separate by at least 4 hours. Adhere strictly to timing for malaria therapy to maintain effective blood levels and reduce the risk of treatment failure.
Precautions
Cardiac safety is a key concern. Chloroquine can prolong the QT interval, potentially leading to serious arrhythmias, especially in patients with existing QT prolongation, structural heart disease, bradycardia, electrolyte abnormalities (low potassium or magnesium), or those taking other QT-prolonging drugs. A clinician may review your medication list and, when appropriate, obtain an ECG or labs before prescribing. Report palpitations, syncope, or new dizziness immediately.
Ophthalmologic effects are rare with short courses but more relevant with prolonged or high cumulative dosing. Chloroquine can cause retinopathy that may be irreversible. Long-term users need baseline and periodic eye exams per specialist guidance. Seek urgent care if you notice blurred vision, difficulty focusing, halos, or changes in color vision.
Other precautions include potential hypoglycemia (which can occur even without diabetes), neuromuscular effects (worsening of myasthenia gravis), seizure risk in susceptible individuals, and caution in hepatic or renal impairment due to altered drug clearance. Use during pregnancy for chloroquine-sensitive malaria prophylaxis and treatment has historically been considered acceptable at recommended doses; nonetheless, all decisions in pregnancy and breastfeeding should be individualized with a clinician.
Contraindications
Chloroquine is contraindicated in individuals with known hypersensitivity to chloroquine or related 4-aminoquinolines. It should generally be avoided in patients with preexisting macular or retinal disease, those with documented QT prolongation or a history of torsades de pointes, and in patients with uncontrolled epilepsy. Severe psoriasis and certain porphyrias may be exacerbated by chloroquine; prescribers weigh risks carefully in these conditions.
Possible side effects
Common side effects include nausea, vomiting, abdominal discomfort, decreased appetite, headache, dizziness, and itching (pruritus). Pruritus may be more frequent in some patients and often lessens with continued dosing. Taking chloroquine with food can help reduce gastrointestinal upset.
Less common but more serious effects include cardiotoxicity (QT prolongation, arrhythmias, cardiomyopathy), significant hypoglycemia (sweating, confusion, visual changes), neuropsychiatric symptoms (agitation, mood changes, nightmares), seizures in susceptible individuals, and hematologic abnormalities. Dermatologic reactions, including photosensitivity and rash, can occur; rare severe skin reactions warrant immediate medical attention.
Ocular toxicity presents with blurred vision, scotomas, or changes in color perception and is associated with long-term or high cumulative exposure. Any new visual symptoms require prompt evaluation and discontinuation guidance from a prescriber. If you experience chest pain, fainting, rapid or irregular heartbeat, severe weakness, or sudden visual changes, seek emergency care.
Drug interactions
Chloroquine interacts with numerous drugs. Concomitant use with other QT-prolonging agents increases arrhythmia risk. Examples include certain antiarrhythmics (amiodarone, sotalol), macrolide and fluoroquinolone antibiotics (azithromycin, levofloxacin), some antifungals, antipsychotics, methadone, and tricyclic antidepressants. Combining multiple QT-prolonging agents requires careful risk assessment and monitoring.
Absorption can be reduced by antacids containing aluminum or magnesium and by kaolin; separate doses by several hours. Cimetidine may increase chloroquine levels by reducing hepatic metabolism, whereas enzyme inducers such as rifampin may decrease efficacy. Chloroquine can increase plasma concentrations of digoxin and cyclosporine, warranting closer monitoring and possible dose adjustments. Co-administration with antidiabetic medications can potentiate hypoglycemia; patients should monitor glucose and be alert for symptoms.
Using chloroquine with mefloquine may raise seizure risk. When primaquine or tafenoquine is used to prevent P. vivax relapse, clinicians must check G6PD status to prevent hemolysis; while this precaution relates primarily to those agents, overall malaria regimens should be coordinated by a specialist for safety.
Missed dose
If you miss a dose of chloroquine for malaria prophylaxis, take it as soon as you remember unless it is close to the time for your next scheduled dose; do not double up. For treatment regimens with precise timing (e.g., doses at 6, 24, and 48 hours), contact your prescriber for instructions if a dose is missed. Maintaining proper intervals is important to prevent treatment failure.
Overdose
Chloroquine overdose is a medical emergency with rapid onset of toxicity—particularly dangerous in children due to the drug’s narrow therapeutic index. Early symptoms may include drowsiness, visual disturbances, headache, nausea, and vomiting, quickly progressing to life-threatening hypotension, arrhythmias, seizures, and cardiac arrest. Even small amounts can be fatal; keep tablets in child-resistant containers and out of sight and reach of children.
If an overdose is suspected, call emergency services and your regional poison control center immediately. Do not induce vomiting. Emergency management may require airway protection, aggressive cardiac monitoring, vasopressors, IV diazepam, and correction of electrolytes in a critical care setting.
Storage
Store chloroquine at controlled room temperature in a dry place away from excess heat, moisture, and light. Keep it in the original, tightly closed container, and never share the medication. Check expiration dates and properly dispose of unused tablets through take-back programs if available.
U.S. sale and prescription policy
In the United States, chloroquine is a prescription-only medication. You cannot legally buy chloroquine without prescription from legitimate pharmacies. This safeguard exists because proper indication, destination-specific resistance patterns, dosing, and safety monitoring (for QT prolongation, interactions, and rare retinal toxicity) require professional evaluation. Avoid online sellers that advertise antimalarials without a prescription—these sources commonly dispense substandard or counterfeit products and can put you at serious risk.
Safe access options include scheduling a visit with a primary care clinician, travel medicine clinic, or infectious diseases specialist, either in person or via telemedicine. These clinicians can confirm whether chloroquine is appropriate for your itinerary (many regions require other agents), arrange vaccines and standby therapy if needed, and counsel you on mosquito-bite prevention. For treatment of suspected malaria, seek urgent medical care rather than self-medicating.
Hospitals and rehabilitation centers, such as HealthSouth Rehabilitation Hospital of Tallahassee, can help coordinate legitimate, clinician-led care pathways. That means a licensed provider evaluates you and, when medically appropriate, authorizes therapy; medications are dispensed under medical orders rather than over the counter. This is not the same as buying chloroquine without a prescription, which is unlawful. Contact qualified healthcare providers to discuss appropriate evaluation and legally obtain any necessary prescriptions.
