chloroquine hydrochloride
Aralen Hydrochloride

chloroquine phosphate
Aralen Phosphate

Available forms
Available by prescription only
chloroquine hydrochloride
Injection: 50 mg/ml (40 mg/ml base)
chloroquine phosphate
Tablets: 250 mg (150-mg base); 500 mg (300-mg base)

Indications and dosages
 Suppressive prophylaxis. Adults: 500 mg (300-mg base) P.O. on same day once weekly beginning 2 weeks before exposure.
Children: 5 mg (base)/kg P.O. on same day once weekly (not to exceed adult dosage) beginning 2 weeks before exposure.
 Treatment of acute attacks of malaria. Adults: 1 g (600-mg base) P.O. followed by 500 mg (300-mg base) P.O. after 6 to 8 hours; then a single dose of 500 mg (300-mg base) P.O. for next 2 days or 4 to 5 ml (160- to 200-mg base) I.M. and repeated in 6 hours if needed; change to P.O. as soon as possible.
Children: 10 mg (base)/kg P.O. initially; then 5 mg (base)/kg after 6 hours. Third dose is 5 mg (base)/kg 18 hours after second dose; fourth dose is 5 mg (base)/kg 24 hours after third dose; or 5 mg (base)/kg I.M. May repeat in 6 hours and change to P.O. as soon as possible. Do not exceed 10 mg/kg in 24 hours.
 Extraintestinal amebiasis. Adults: 1 g (600-mg base) daily for 2 days, then 500 mg (300-mg base) daily for 2 to 3 weeks or 4 to 5 ml (160- to 200-mg base) I.M. for 10 to 12 days; change to P.O. as soon as possible. Administer with an intestinal amebicide.
 Rheumatoid arthritis ◇. Adults: 250 mg P.O. daily (chloroquine phosphate) with evening meal.
 Lupus erythematosus ◇. Adults: 250 mg P.O. daily (chloroquine phosphate) with evening meal; reduce dosage gradually over several months when lesions regress.

Pharmacodynamics
Antimalarial action: Chloroquine binds to DNA, interfering with protein synthesis. It also inhibits DNA and RNA polymerases.
Amebicidal action: Unknown.
Anti-inflammatory action: Unknown. Drug may antagonize histamine and serotonin and inhibit prostaglandin effects by inhibiting conversion of arachidonic acid to prostaglandin F₂; it also may inhibit chemotaxis of polymorphonuclear leukocytes, macrophages, and eosinophils.
  Chloroquine’s spectrum of activity includes the asexual erythrocytic forms of Plasmodium malariae, P.ovale, P. vivax, many strains of P. falciparum, and Entamoeba histolytica.

Pharmacokinetics
Absorption: Absorbed readily and almost completely.
Distribution: 55% bound to plasma proteins. Concentrated in erythrocytes, liver, spleen, kidneys, heart, and brain and is strongly bound in melanin-containing cells.
Metabolism: About 30% of an administered dose is metabolized by the liver to monodesethyl-chloroquine and bidesethylchloroquine.
Excretion: About 70% of dose is excreted unchanged in urine; unabsorbed drug is excreted in feces. Small amounts of the drug may be present in urine for months after the drug is discontinued. Renal excretion is enhanced by urinary acidification.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug and in those with retinal or visual field changes or porphyria. Use cautiously in patients with hepatic disease, alcoholism, or in conjunction with hepatotoxic drugs. Use cautiously in patients with blood disorders or G6-PD deficiency.

Interactions
Drug-drug. Aluminum salts, kaolin, magnesium salts: May decrease chloroquine absorption. Separate administration times.
Cimetidine: May reduce oral clearance and metabolism. Monitor patient for toxicity.
Intradermal human diploid cell rabies vaccine: May interfere with antibody response. Use together cautiously.
Drug-lifestyle. Sun exposure: May worsen drug-induced dermatoses. Urge patient to avoid excessive sun exposure.

Adverse reactions
CNS: mild and transient headache, psychic stimulation, seizures.
CV: hypotension, ECG changes, AV block, cardiomyopathy.
EENT: visual disturbances (blurred vision; difficulty in focusing; reversible corneal changes; typically irreversible, sometimes progressive or delayed retinal changes, such as narrowing of arterioles; macular lesions; pallor of optic disk; optic atrophy; patchy retinal pigmentation, typically leading to blindness), ototoxicity (nerve deafness, vertigo, tinnitus).
GI: anorexia, abdominal cramps, diarrhea, nausea, vomiting.
Hematologic: agranulocytosis, aplastic anemia.
Skin: pruritus, lichen planus eruptions, skin and mucosal pigmentary changes, pleomorphic skin eruptions, hair loss.

Effects on lab test results
• May decrease hemoglobin, hematocrit, and granulocyte and platelet counts.

Overdose and treatment
Symptoms of overdose may appear within 30 minutes after ingestion and may include headache, drowsiness, visual changes, CV collapse, and seizures followed by respiratory and cardiac arrest.
 Treatment is symptomatic. Empty stomach by emesis or lavage. After lavage, activated charcoal in an amount at least five times the estimated amount of drug ingested may be helpful if given within 30 minutes of ingestion.
 Ultra-short-acting barbiturates may help control seizures. Intubation may become necessary. Peritoneal dialysis and exchange transfusions also may be useful. Forced fluids and acidification of the urine are helpful after the acute phase.

Special considerations
 ALERT Dosage may be ordered in milligrams or milligrams base. Write order clearly to avoid medication errors.
• Resistance of P. falciparum to chloroquine has spread to most areas with malaria except the Dominican Republic, Haiti, Central America west of the Panama Canal, and Egypt.
• It may also be advisable for traveler to take along sulfadoxine and pyrimethamine (Fansidar). Instruct patient to take drug if a febrile illness occurs and professional medical care isn’t available. Emphasize that such self-treatment is a temporary measure and that he must seek medical care as soon as possible. He should continue prophylaxis after the treatment dose of Fansidar.
• Baseline and periodic ophthalmologic examinations are needed in prolonged or high-dosage therapy.
• Assist patient in obtaining audiometric examinations before, during, and after therapy, especially if therapy is long-term.
Breast-feeding patients
• Drug appears in breast milk. Safety hasn’t been established. Use cautiously in breast-feeding women.
Pediatric patients
• Children are extremely susceptible to toxicity; monitor children closely for adverse effects.

Patient education
• Tell patient to promptly report blurred vision, increased sensitivity to light, hearing loss, pronounced GI disturbances, or muscle weakness.
• Advise patient to take drug immediately before or after meals on the same day each week to minimize gastric distress. Patients who can’t tolerate drug because of GI distress may tolerate hydroxychloroquine.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use