These changes bear no relationship to dosage and are usually reversible on cessation of hydroxychloroquine. The macular changes are potentially serious. Advanced retinopathy is characterized by reduction of visual acuity and a "bulls eye" macular lesion which is absent in early involvement. Overdose
Overdoses of hydroxychloroquine are extremely rare, but extremely toxic. Eight people are known to have overdosed since the drugs introduction in the mid-1950s, of which three have died. Chloroquine has a risk of death in overdose in adults of about 20%, while hydroxychloroquine is estimated to be two or threefold less toxic.Serious signs and symptoms of overdose generally occur within an hour of ingestion. These may include sleepiness, vision changes, seizures, coma, stopping of breathing, and heart problems such as ventricular fibrillation and low blood pressure. Loss of vision may be permanent. Low blood potassium, to levels of 1 to 2 mmol/L, may also occur. Cardiovascular abnormalities such as QRS complex widening and QT interval prolongation may also occur.Treatment recommendations include early mechanical ventilation, heart monitoring, and activated charcoal. Supportive treatment with intravenous fluids and vasopressors may be required with epinephrine being the vasopressor of choice. Stomach pumping may also be used. Sodium bicarbonate and hypertonic saline may be used in cases of severe QRS complex widening. 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 does not appear to be useful.
Detection
Hydroxychloroquine may be quantified in plasma or serum to confirm a diagnosis of poisoning in hospitalized victims or in whole blood to assist in a forensic investigation of a case of sudden or unexpected death. Plasma or serum concentrations are usually in a range of 0.1-1.6 mg/L during therapy and 6–20 mg/L in cases of clinical intoxication, while blood levels of 20–100 mg/L have been observed in deaths due to acute overdosage. Interactions
The drug transfers into breast milk. There is no evidence that its use during pregnancy is harmful to the developing fetus and its use is not contraindicated in pregnancy.The concurrent use of hydroxychloroquine and the antibiotic azithromycin appears to increase the risk for certain serious side effects with short-term use, such as an increased risk of chest pain, congestive heart failure, and mortality from cardiovascular causes. Care should be taken if combined with medication altering liver function as well as aurothioglucose (Solganal), cimetidine (Tagamet) or digoxin (Lanoxin). Hydroxychloroquinecan increase plasma concentrations of penicillamine which may contribute to the development of severe side effects. It enhances hypoglycemic effects of insulin and oral hypoglycemic agents. Dose altering is recommended to prevent profound hypoglycemia. Antacids may decrease the absorption of hydroxychloroquine.