Some evidence indicates it has a genetic basis and is related to chloroquine action with opiate receptors centrally or peripherally. Unpleasant metallic taste
This could be avoided by "taste-masked and controlled release" formulations such as multiple emulsions. Chloroquine retinopathy
Electrocardiographic changesThis manifests itself as either conduction disturbances (bundle-branch block, atrioventricular block) or Cardiomyopathy – often with hypertrophy, restrictive physiology, and congestive heart failure. The changes may be irreversible. Only two cases have been reported requiring heart transplantation, suggesting this particular risk is very low. Electron microscopy of cardiac biopsies show pathognomonic cytoplasmic inclusion bodies. Pancytopenia, aplastic anemia, reversible agranulocytosis, low blood platelets, neutropenia. Pregnancy
Chloroquine has not been shown to have any harmful effects on the fetus when used in the recommended doses for malarial prophylaxis. Small amounts of chloroquine are excreted in the breast milk of lactating women. However, this drug can be safely prescribed to infants, the effects are not harmful. Studies with mice show that radioactively tagged chloroquine passed through the placenta rapidly and accumulated in the fetal eyes which remained present five months after the drug was cleared from the rest of the body. Women who are pregnant or planning on getting pregnant are still advised against traveling to malaria-risk regions. Elderly
There is not enough evidence to determine whether chloroquine is safe to be given to people aged 65 and older. Since it is cleared by the kidneys, toxicity should be monitored carefully in people with poor kidney functions.
Drug interactions
Chloroquine has a number of drug–drug interactions that might be of clinical concern:
Ampicillin- levels may be reduced by chloroquine;
Antacids- may reduce absorption of chloroquine;
Cimetidine- may inhibit metabolism of chloroquine; increasing levels of chloroquine in the body;
Cyclosporine- levels may be increased by chloroquine; and
Mefloquine- may increase risk of convulsions. Overdose
Chloroquine, in overdose, has a risk of death of about 20%. It is rapidly absorbed from the gut with an onset of symptoms generally within an hour. Symptoms of overdose may include sleepiness, vision changes, seizures, stopping of breathing, and heart problems such as ventricular fibrillation and low blood pressure. Low blood potassium may also occur.While the usual dose of chloroquine used in treatment is 10 mg/kg, toxicity begins to occur at 20 mg/kg, and death may occur at 30 mg/kg. In children as little as a single tablet can cause problems.Treatment recommendations include early mechanical ventilation, cardiac monitoring, and activated charcoal. Intravenous fluids and vasopressors may be required with epinephrine being the vasopressor of choice. Seizures may be treated with benzodiazepines. Intravenous potassium chloride may be required, however this may result in high blood potassium later in the course of the disease. Dialysis has not been found to be useful. Pharmacology
Absorption of chloroquine is rapid and primarily happens in the gastrointestinal tract. It is widely distributed in body tissues. Protein binding in plasma ranges from 46% to 79%. Its metabolism is partially hepatic, giving rise to its main metabolite, desethylchloroquine. Its excretion is ≥50% as unchanged drug in urine, where acidification of urine increases its elimination.