chloroquine phosphate

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chloroquine phosphate

Pharmacologic class: 4-amino-quinolone derivative

Therapeutic class: Antimalarial, amebicide

Pregnancy risk category C

FDA Box Warning

• Drug is indicated for treating malaria and extraintestinal amebiasis.

• Before prescribing, clinician should be familiar with complete package insert contents.


Unknown. Antimalarial action may occur through inhibition of protein synthesis and alteration of DNA in susceptible parasites.


Tablets: 250 mg (150-mg base), 500 mg (300-mg base)

Indications and dosages

Uncomplicated acute malarial attacks

Adults: Initially, 1 g (600-mg base) P.O., then an additional 500 mg (300-mg base) P.O. 6 hours later and a single dose of 500 mg (300-mg base) P.O. on second and third days. Or initially, 160- to 200-mg base I.M., repeated in 6 hours (800-mg base maximum dosage during first 24 hours); continue for 3 days until total dosage of 1.5-g base has been given. Switch to oral therapy as soon as possible.

Children: Initially, 10 mg (base)/kg P.O., then 5 mg (base)/kg 6 hours, 24 hours, and 36 hours later; don't exceed recommended adult dosage. Or initially, 5 mg (base)/kg I.M. repeated 6 hours later, 18 hours after second dose, and then 24 hours after third dose; don't exceed recommended adult dosage.

Malaria prophylaxis

Adults: 500 mg (300-mg base) P.O. weekly 1 to 2 weeks before visiting endemic area and continued for 4 weeks after leaving area. If therapy starts after malaria exposure, initial dosage is 600-mg base P.O. in two divided doses given 6 hours apart.

Children: 5 mg (base)/kg P.O. weekly for 1 to 2 weeks before visiting endemic area and continued for 4 weeks after leaving area, to a maximum dosage of 300 mg weekly. If treatment starts after exposure, 10 mg (base)/kg P.O. in two divided doses 6 hours apart and continued for 8 weeks after leaving area.

Extraintestinal amebiasis

Adults: Initially, 1 g (600-mg base) P.O. daily for 2 days, then 500 mg (300-mg base) daily for 2 to 3 weeks. When oral therapy isn't tolerated, give 160- to 200-mg base I.M. daily for 10 to 12 days; switch to oral therapy as soon as possible.

Children: 10 mg (base)/kg P.O. once daily for 2 to 3 weeks, to a maximum dosage of 300 mg (base) daily

Off-label uses

• Lupus erythematosus

• Rheumatoid arthritis


• Hypersensitivity to drug

• Retinal and visual field changes

• Porphyria


Use cautiously in:

• severe GI, neurologic, or blood disorders; hepatic impairment; G6PD deficiency; neurologic disease; eczema; alcoholism

• pregnant patients

• children.


• For obese patient, determine weight-based dosages from lean body weight. (Drug is stored in body tissues and eliminated slowly.)

Adverse reactions

CNS: mild and transient headache, personality changes, dizziness, vertigo neuropathy, seizures

CV: hypotension, ECG changes

EENT: blurred vision, difficulty focusing, reversible corneal changes, irreversible retinal damage leading to vision loss, scotomas, ototoxicity, tinnitus, nerve deafness

GI: nausea, vomiting, diarrhea, abdominal pain, stomatitis, anorexia

Hematologic: agranulocytosis, aplastic anemia, hemolytic anemia, thrombocytopenia

Skin: lichen planus eruptions, skin and mucosal pigmentation changes, pruritus, pleomorphic skin eruptions


Drug-drug. Aluminum and magnesium salts, kaolin: decreased GI absorption of chloroquine

Ampicillin: reduced ampicillin bioavailability

Cimetidine: decreased hepatic metabolism of chloroquine

Cyclosporine: sudden increase in cyclosporine blood level

Drug-diagnostic tests. Granulocytes, hemoglobin, platelets: decreased values

Drug-behaviors. Sun exposure: exacerbation of drug-induced dermatoses

Patient monitoring

• Monitor hepatic enzyme levels in patients with hepatic disease.

• Assess creatinine levels in patients with renal insufficiency or failure.

• In long-term therapy (as for lupus or rheumatoid arthritis), be aware that desired effects may be delayed for up to 6 months.

• Be aware that drug is secreted in breast milk but not in sufficient amounts to prevent malaria in infant.

Patient teaching

• Tell patient to take drug with food at evenly spaced intervals.

Instruct patient to immediately report blurred vision or hearing changes.

• In areas where malaria is endemic, advise pregnant patient to consult prescriber about taking drug.

• Inform patient on long-term therapy that beneficial effects may take up to 6 months.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.

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