Chloroquine Phosphate (Page 2 of 3)

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 body2. There are no adequate and well-controlled studies evaluating the safety and efficacy of chloroquine in pregnant women.

PRECAUTIONS

Hematological Effects/Laboratory Tests

Complete blood cell counts should be checked periodically if patients are given prolonged therapy
(see ADVERSE REACTIONS).
Chloroquine may cause hemolysis in glucose-6 phosphate dehydrogenase (G-6-PD) deficiency. Blood monitoring may be needed as hemolytic anemia may occur, in particular in association with
other drugs that cause hemolysis (see ADVERSE REACTIONS).

Auditory Effects

In patients with preexisting auditory damage, chloroquine should be administered with caution. In case of any defects in hearing, chloroquine should be immediately discontinued, and the patient closely observed (see ADVERSE REACTIONS).

Use in Patients with Hepatic Impairment

Since chloroquine phosphate tablets are known to concentrate in the liver, it should be used with
caution in patients with hepatic disease or alcoholism or in conjunction with known hepatotoxic
drugs.

Central Nervous System Effects

Chloroquine may increase the risk of convulsions in patients with a history of epilepsy.

Drug Interactions

Antacids and kaolin: Antacids and kaolin can reduce absorption of chloroquine; an interval of at least4 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.

Ampicillin: In a study of healthy volunteers, chloroquine significantly reduced the bioavailability of ampicillin. An interval of at least two hours between intake of ampicillin and chloroquine should be observed.

Cyclosporine: After introduction of chloroquine (oral form), a sudden increase in serum cyclosporine level has been reported. Therefore, close monitoring of serum cyclosporine level is recommended and, if necessary, chloroquine should be discontinued.

Mefloquine: Co-administration of chloroquine and mefloquine may increase the risk of convulsions.

The blood concentrations of chloroquine and desethylchloroquine (the major metabolite of chloroquine, which also has antimalarial properties) were negatively associated with log antibody titers. Chloroquine taken in the dose recommended for malaria prophylaxis can reduce the antibody response to primary immunization with intradermal human diploid-cell rabies vaccine.
Praziquantel: In a single-dose interaction study, chloroquine has been reported to reduce the
bioavailability of praziquantel.
Tamoxifen: Concomitant use of chloroquine with drugs known to induce retinal toxicity such as
tamoxifen is not recommended (see WARNINGS).

Pregnancy

See WARNINGS,Usage in Pregnancy.

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 wasinvestigated 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. Separate chemoprophylaxis for the infant is required (see DOSAGE AND ADMINISTRATION).

Pediatric Use

See WARNINGS and DOSAGE AND ADMINISTRATION.

Geriatric Use

Clinical studies of chloroquine phosphate did not include sufficient numbers of subjects aged 65and over to determine whether they respond differently from younger subjects. However, this drugis known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug maybe greater in patients with impaired renal function. Because elderly patients are more likely to havedecreased renal function, care should be taken in dose selection and it may be useful to monitorrenal function.

ADVERSE REACTIONS

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 degenration have been reported and may be irreversible (see WARNINGS), irreversible retinal damage in patients receiving long-term or high-dosage 4-aminoquinoline therapy; visual disturbances (blurring of vision and difficulty of focusing or accommodation); nyctalopia; scotomatous vision with field defects of paracentral, pericentral ring types, and typically temporal scotomas, e.g., difficulty in reading with words tending to disappear, seeing half an object, misty vision, and fog before the eyes. Reversible corneal opacities have also been reported.
Immune system disorders: Urticaria, anaphylactic reaction including angioedema.
Ear and labyrinth disorders: Nerve type deafness; tinnitus, reduced hearing in patients with preexisting auditory damage.

Musculoskeletal and connective tissue-disorders: Sensorimotor disorders, skeletal muscle myopathy or neuromyopathy leading to progressive weakness and atrophy of proximal muscle groups, depression of tendon reflexes and abnormal nerve conduction.
Gastrointestinal disorders: Hepatitis, increased liver enzymes, anorexia, nausea, vomiting, diarrhea, abdominal cramps.
Skin and subcutaneous tissue disorders: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis. Pleomorphic skin eruptions, skin and mucosal pigmentary changes; lichen planus-like eruptions, pruritus,; drug rash with eosinophilia and systemic symptoms (DRESS syndrome); photosensitivity and hair loss and bleaching of hair pigment.
Blood and lymphatic system disorders: Pancytopenia, aplastic anemia, reversible agranulocytosis, thrombocytopenia and neutropenia. Hemolytic anemia in G6PD deficient patients (see PRECAUTIONS).
Nervous system disorders: Convulsions, mild and transient headache, polyneuropathy, acute extrapyramidal disorders (such as dystonia, dyskinesia, tongue protrusion, torticollis) (see WARNINGS and OVERDOSAGE).
Neuropsychiatric disorders: Neuropsychiatric changes including psychosis, delirium, anxiety, agitation, insomnia, confusion, hallucinations, personality changes, depression, and suicidal behavior.
Cardiac disorders: Hypotension, electrocardiographic changes (particularly, inversion or depression of the T-wave with widening of the QRS complex), and cardiomyopathy (which may result in cardiac failure and in some cases a fatal outcome). Cardiac arrhythmias, conduction disorders such as bundle branch block / atrio-ventricular block, QT interval prolongation, torsade de pointes, ventricular tachycardia and ventricular fibrillation have been reported with therapeutic doses of chloroquine as well as with overdose. The risk is greater if chloroquine is administered at high doses. Fatal cases have been reported (see WARNINGS, Cardiac Effects and OVERDOSAGE).
Metabolic and Nutritional disorders: Hypoglycemia (see WARNINGS).

OVERDOSAGE

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. Immediate medical attention is required, as these effects may appear shortly after the overdose. Cases of extrapyramidal disorders have also been reported in the context of chloroquine overdose (see WARNINGS and ADVERSE REACTIONS).
Treatment: Treatment is symptomatic and must be prompt with immediate evacuation of the stomach by emesis or gastric lavage followed by treatment with activated charcoal. Chloroquine overdose is a life-threatening emergency and should be managed with cardio-respiratory and hemodynamic support, monitoring of potassium along with management of arrhythmias and convulsions, as necessary. A patient who survives the acute phase and is asymptomatic should be closely observed until all clinical features of toxicity resolve.

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