Chloroquine Phosphate | Aralen

Chloroquine Phosphate | Aralen

Chloroquine (also known as chloroquine phosphate) is an antimalarial medicine. It is available in the United States by prescription only. It is sold under the brand name Aralen, and it is also sold as a generic medicine. It is available in tablets of two sizes: 150mg base (250mg salt) and 300mg base (500mg salt). It is just two different ways of describing the same thing. Chloroquine can be prescribed for either prevention or treatment of malaria.

Chloroquine Phosphate | Aralen

Chloroquine phosphate, USP, is a 4-aminoquinoline compound for oral administration. It is a white, odorless, bitter tasting, crystalline substance, freely soluble in water. chloroquine phosphate is an antimalarial and amebicidal drug. Chemically, it is 7-chloro-4-[[4-(diethylamino)-1-methylbutyl] amino] quinoline phosphate (1:2)

Indications: Prophylaxis and treatment of acute attacks of malaria. Treatment of extraintestinalamebiasis.

Unlabeled Use: Treatment of severe rheumatoid arthritis. Treatment of systemic lupuserythematosus.

Mode of action

In infected red blood cells the malarial germ decomposes hemoglobin to gain essential amino acids for its own protein. At this time, Hem, which is toxic for the germ, arises by reason of decomposition. The enzyme hempolymerase crystallizes hem to hemozoin, which is non-toxic for the germ.


Chloroquine enters the cell by diffusion and blocks the enzyme causing hemozoin to no longer be produced and results in hem buildup. After this, all the germs are stalled by the toxic hem. In addition Chloroquine forms a complex known as the FP-chloroquine complex (Fe (II)-protoporphyrin IX) that is highly toxic to the cell and its disrupting membrane functions. This leads to the dieback of the infected cells.

Activity in Vitro and in Clinical Infections

Chloroquine is active against the erythrocytic forms of susceptible strains of Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax. Chloroquine is not active against the gametocytes and the exoerythrocytic forms including the hypnozoite stage (P. vivax and P. ovale) of the Plasmodium parasites. In vitro studies with Chloroquine demonstrated that it is active against the trophozoites of Entamoeba histolytica.

Adverse Reactions/Side Effects

CNS: SEIZURES, anxiety, agitation, confusion, delirium, depression, hallucinations, headache, insomnia, personality changes, polyneuritis, psychosis.

EENT: corneal opacities (reversible), hearing impairment, retinopathy, tinnitus, visual disturbances.

CV: cardiomyopathy, ECG changes (T-wave abnormalities, QRS prolongation), hypotension.

GI: abdominal cramps, anorexia, diarrhea, hepatitis,qliver enzymes, nausea, vomiting.

Derm: STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, alopecia, dermatoses, photosensitivity, pigmentary changes, pruritus, skin eruptions, urticaria.


Neuro: neuromyopathy, peripheral neuritis, weakness.

Treatment of Acute Attack of Malaria

PO (Adults):
600 mg initially, then 300 mg at 6–8 hr, 24 hr, and 48 hr after initial dose.

PO (Children): 10 mg/kg initially (not to exceed 600 mg), then 5 mg/kg at 6 hr, 24 hr, and 48 hr after initial dose (not to exceed 300 mg/day).

Extraintestinal Amebiasis

PO (Adults):
600 mg daily for 2 days, then 300 mg daily for at least 2–3 wk (in combination with other antiprotozoals).

PO (Children): 10 mg/kg (not to exceed 300 mg/day for 2–3 wk.

Rheumatoid Arthritis/Systemic Lupus Erythematosus

PO (Adults):
150 mg once daily; reduce dosage following maximal response.

Potential side effects of chloroquine

Chloroquine is a relatively well-tolerated medicine. The most common adverse reactions reported are stomach pain, nausea, vomiting, and headache. These side effects can often be lessened by taking chloroquine with food. Chloroquine may also cause itching in some people.

All medicines may have some side effects. Minor side effects such as nausea, occasional vomiting, or diarrhea usually do not require stopping the antimalarial drug. If you cannot tolerate your antimalarial drug, see your health care provider; other antimalarial drugs are available.

Nursing Mothers

Because of the potential for serious adverse reactions in nursing infants from chloroquine, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the potential clinical benefit of the drug to the mother.

The excretion of chloroquine and the major metabolite, desethylchloroquine, in breast milk was investigated in eleven lactating mothers following a single oral dose of chloroquine (600 mg base). The maximum daily dose of the drug that the infant can receive from breastfeeding was about 0.7% of the maternal start dose of the drug in malaria chemotherapy


Usage in Pregnancy

Usage of chloroquine during pregnancy should be avoided except in the prophylaxis or treatment of malaria when the benefit outweighs the potential risk to the fetus. Radioactively tagged chloroquine administered intravenously to pregnant pigmented CBA mice passed rapidly across the placenta and accumulated selectively in the melanin structures of the fetal eyes.

It was retained in the ocular tissues for five months after the drug had been eliminated from the rest of the body. There are no adequate and well-controlled studies evaluating the safety and efficacy of chloroquine in pregnant women.



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