CHLOROQUINE PHOSPHATE

(klor'oh-kwin)

Aralen
Classifications: antimalarial;
Therapeutic: antimalarial
Pregnancy Category: C

Availability

150 mg (base), 300 mg (base) tablets

Action

Antimalarial activity is believed to be based on its ability to form complexes with DNA of parasite, thereby inhibiting replication and transcription to RNA and nucleic acid synthesis.

Therapeutic Effect

Acts as a suppressive agent in patient with P. vivax or P. malariae malaria; terminates acute attacks and increases intervals between treatment and relapse of malaria. Abolishes the acute attack of P. falciparum malaria but does not prevent the infection. Chloroquine-resistant strains have been reported.

Uses

Suppression and treatment of malaria caused by P. malariae, P. ovale, P. vivax, and susceptible forms of P. falciparum, and in the treatment of extraintestinal amebiasis. Concomitant therapy with primaquine is necessary for radical cure of P. vivax and P. malariae malarias.

Unlabeled Uses

Discoid and systemic lupus erythematosus, porphyria cutanea tarda, solar urticaria, polymorphous light eruptions, and in rheumatoid arthritis (as second-line therapy).

Contraindications

Hypersensitivity to 4-aminoquinolines, psoriasis; porphyria, renal disease, 4-aminoquinoline-induced retinal or visual field changes; long-term therapy in children; pregnancy (category C). Safe use in women of childbearing potential not established.

Cautious Use

Impaired hepatic function, alcoholism, eczema, patients with G6PD deficiency, infants and children, hematologic, GI, and neurologic disorders.

Route & Dosage

Doses are expressed in terms of chloroquine base.

Acute Malaria
Adult: PO 600 mg base followed by 300 mg base at 6, 24, and 48 h
Child: PO 10 mg base/kg, then 5 mg base/kg at 6, 24, and 48 h

Malaria Suppression
Adult: PO 300 mg base the same day each week starting 2 wk before exposure and continuing for 4–6 wk after leaving the area of exposure (max: 300 mg base/wk)
Child: PO 5 mg base/kg the same day each week starting 2 wk before exposure and continuing for 4–6 wk after leaving the area of exposure (max: 300 mg base/wk)

Extraintestinal Amebiasis
Adult: PO 600 mg base/d for 2 d, then 300 mg base/d for 2–3 wk
Child: PO 10 mg base/kg/d for 2–3 wk

Rheumatoid Arthritis, SLE
Adult: PO 150 mg base/d with evening meal

Administration

Oral

Give immediately before or after meals to minimize GI distress.
Monitor child's dose closely. Children are extremely susceptible to overdosage.

Adverse Effects (≥1%)

Body as a Whole: Slight weight loss, myalgia, lymphedema of upper limbs. CV: Hypotension; ECG changes. GI: Diarrhea, abdominal cramps, nausea, vomiting, anorexia. Hematologic: Hemolytic anemia in patients with G6PD deficiency. CNS: Mild transient headache, fatigue, irritability, confusion, nightmares, skeletal muscle weakness, paresthesias, reduced reflexes, vertigo. Skin: Bleaching of scalp, eyebrows, body hair, and freckles, pruritus, patchy alopecia (reversible). Special Senses: (usually reversible): Blurred vision, disturbances of accommodation, night blindness, scotomas, visual field defects, photophobia, corneal edema, opacity or deposits, ototoxicity (rare).

Interactions

Drug: Aluminum- and magnesium-containing antacids and laxatives decrease chloroquine absorption, so separate administration by at least 4 h; chloroquine may interfere with response to rabies vaccine.

Pharmacokinetics

Absorption: Rapidly and almost completely absorbed. Peak: 1–2 h. Distribution: Widely distributed; concentrates in lungs, liver, erythrocytes, eyes, skin, and kidneys; crosses placenta. Metabolism: Partially in liver to active metabolites. Elimination: In urine; excreted in breast milk. Half-Life: 70–120 h.

Nursing Implications

Assessment & Drug Effects

Lab tests: CBC and ECG are advised before initiation of therapy and periodically thereafter in patients on long-term therapy. A test for G6PD deficiency is recommended for American blacks and individuals of Mediterranean ancestry before therapy.
Monitor for changes in vision. Retinopathy (generally irreversible) can be progressive even after termination of therapy. Patient may be asymptomatic or complain of night blindness, scotomas, visual field changes, blurred vision, or difficulty in focusing. Chloroquine should be discontinued immediately.
Question patients on long-term therapy regularly about skeletal muscle weakness. Periodic tests should be made of muscle strength and deep tendon reflexes. Positive signs are indications to terminate therapy.

Patient & Family Education

Report promptly visual or hearing disturbances, muscle weakness, or loss of balance, symptoms of blood dyscrasia (fever, sore mouth or throat, unexplained fatigue, easy bruising or bleeding).
Use of dark glasses in sunlight or bright light may provide comfort (because of photophobia) and reduce risk of ocular damage.
Avoid driving or other potentially hazardous activities until reaction to drug is known.
May cause rusty yellow or brown discoloration of urine.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

(35)