Chloroquine

Chloroquine phosphate tablets are indicated for the: Treatment of uncomplicated malaria due to susceptible strains of P. falciparum, P.malariae, P. ovale , and P.vivax. Prophylaxis of malaria in geographic areas where resistance to chloroquine is not present. Treatment of extraintestinal amebiasis. Chloroquine phosphate tablets do not prevent relapses in patients with vivax or ovale malaria because it is not effective against exoerythrocytic forms of the parasites. Limitations of Use in Malaria: Do not use chloroquine phosphate tablets for the treatment of complicated malaria (high-grade parasitemia and/or complications e.g., cerebral malaria or acute renal failure). …

• The dosage of chloroquine phosphate is often expressed in terms of equivalent chloroquine base
• Each 500 mg tablet of chloroquine phosphate tablet contains the equivalent of 300 mg chloroquine base
• In infants and children the dosage is preferably calculated by body weight
• Prophylaxis against chloroquine-sensitive Plasmodium species Adult Dose: The dosage for prophylaxis is 500 mg (= 300 mg base) administered once per week on exactly the same day of each week
• Pediatric Dose: The dosage for prophylaxis is 5 mg calculated as base, per kg of body weight, administered once per week on exactly the same day of each week
• The pediatric dose should never exceed the adult dose regardless of weight
• If circumstances permit, suppressive therapy should begin two weeks prior to exposure
• However, failing this
• In adults, an initial double (loading) dose of 1 g (= 600 mg base), or in children 10 mg base/kg may be taken in two divided doses, six hours apart
• The suppressive therapy should be continued for eight weeks after leaving the endemic area
• Treatment of uncomplicated malaria due to chloroquine-sensitive Plasmodium species
• Adults: An initial dose of 1 g salt (= 600 mg base) followed by an additional 500 mg (= 300 mg base) after six to eight hours and a single dose of 500 mg (= 300 mg base) on each of two consecutive days
• This represents a total dose of 2.5 g chloroquine phosphate or 1.5 g base in three days
• Infants and Children: In infants and children, the recommended dose is 10 mg base/kg followed by 5 mg based/kg at 6, 24 and 36 hours (total dose 25 mg based/kg). …

See WARNINGS and DOSAGE AND ADMINISTRATION .

Clinical studies of chloroquine phosphate tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. However, this drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. …

• Use of chloroquine phosphate tablets for indications other than acute malaria is contraindicated in the presence of retinal or visual field changes of any etiology
• Use of chloroquine phosphate tablets are contraindicated in patients with known hypersensitivity to 4-aminoquinoline compounds

Antacids and kaolin: Antacids and kaolin can reduce absorption of chloroquine; an interval of at least 4 hours between intake of these agents and chloroquine should be observed. Cimetidine: Cimetidine can inhibit the metabolism of chloroquine, increasing its plasma level. Concomitant use of cimetidine should be avoided. Insulin and other antidiabetic drugs: As chloroquine may enhance the effects of a hypoglycemic treatment, a decrease in doses of insulin or other antidiabetic drugs may be required. Arrhythmogenic drugs: There may be an increased risk of inducing ventricular arrhythmias if chloroquine is used concomitantly with other arrhythmogenic drugs, such as amiodarone or moxifloxacin. …

Chloroquine-Resistant Malaria Chloroquine phosphate tablets are not effective against chloroquine- or hydroxychloroquine-resistant strains of Plasmodium species (see CLINICAL PHARMACOLOGY , Microbiology ). Chloroquine resistance is widespread in P. falciparum and is reported in P. vivax. Before using chloroquine for prophylaxis, it should be ascertained whether chloroquine is appropriate for use in the region to be visited by the traveler. Information regarding the geographic areas where resistance to chloroquine occurs, is available at the Centers for Disease Control and Prevention (www.cdc.gov\malaria). …

The following adverse reactions have been identified during post-approval use of chloroquine or other 4-aminoqunoline compounds. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Ocular disorders: Maculopathy and macular degeneration have been reported and may be irreversible. Irreversible retinopathy with retinal pigmentation changes (bull’s eye appearance) and visual field defects (paracentral scotomas) in patients receiving long-term or high-dosage 4- aminoquinoline therapy have been reported (see WARNINGS ). …

Pregnancy See WARNINGS , Usage in Pregnancy .

Signs and Symptoms: Chloroquine is very rapidly and completely absorbed after ingestion. Toxic doses of chloroquine can be fatal. As little as 1 g may be fatal in children. Toxic symptoms can occur within minutes. The symptoms of overdosage may include nausea, vomiting, headache, drowsiness, visual disturbances, cardiovascular collapse, convulsions, hypokalemia, rhythm and conduction disorders including QT prolongation, torsades de pointes, ventricular tachycardia and ventricular fibrillation, followed by sudden potentially fatal respiratory and cardiac arrest. …

Take it when you remember, unless it is nearly time for the next dose. Then skip the missed one. Never take two doses at once to make up for it. Check your leaflet, as some medicines are different.