Toxicokinetics of hydroxychloroquine following a massive overdose.

BACKGROUND: We report a patient with a massive hydroxychloroquine overdose manifested by profound hypokalemia and ventricular dysrhythmias and describe hydroxychloroquine toxicokinetics. CASE REPORT: A 20-year-old woman (60 kg) presented 1 h after ingesting 36 g of hydroxychloroquine. Vital signs were: BP, 66 mmHg/palpation; heart rate, 115/min; respirations 18/min; oxygen saturation, 100% on room air. She was immediately given intravenous fluids and intubated. Infusions of diazepam and epinephrine were started. Activated charcoal was administered. Her initial serum potassium of 5.3 mEq/L decreased to 2.1 mEq/L 1 h later. The presenting electrocardiogram (ECG) showed sinus tachycardia at 119 beats/min with a QRS duration of 146 ms, and a QT interval of 400 ms (Bazett's QTc 563 ms). She had four episodes of ventricular tachydysrhythmias requiring cardioversion, electrolyte repletion, and lidocaine infusion. Her blood hydroxychloroquine concentration peaked at 28,000 ng/mL (therapeutic range 500-2000 ng/mL). Serial concentrations demonstrated apparent first-order elimination with a half-life of 11.6 h. She was extubated on hospital day three and had a full recovery. CONCLUSION: We present a massive hydroxychloroquine overdose treated with early intubation, activated charcoal, epinephrine, high dose diazepam, aggressive electrolyte repletion, and lidocaine. The apparent 11.6 hour half-life of hydroxychloroquine was shorter than previously described.

A RANKL Wrinkle: Denosumab-Induced Hypocalcemia.

The human monoclonal antibody denosumab inhibits osteoclast-mediated bone resorption by binding to receptor activator of nuclear factor κB ligand (RANKL), which is upregulated by tumor cells. Denosumab is indicated to prevent skeletal-related events (SREs) from osteoporosis and metastatic bone disease. We report a case of denosumab-induced hypocalcemia to highlight potential toxicity and treatment considerations. A 66-year-old man with prostate cancer, small cell lung cancer, and bone metastases presented with fatigue, weakness, and muscle spasm. Sixteen days prior, he received cycle 6 of cisplatin and etoposide, leuprolide, and denosumab (120 mg subcutaneously). His examination demonstrated a slight resting tremor, normal strength, and negative Chvostek sign. Laboratory analysis revealed hemoglobin, 8.0 g/dL; total calcium, 5.2 mg/dL (pre-denosumab, 8.9 mg/dL); and magnesium, 0.7 mg/dL. He initially received two units packed red blood cells, intravenous calcium and magnesium, and vitamin D. During his hospitalization, he required multiple doses of intravenous and oral calcium, magnesium, and vitamin D. Despite ongoing oral supplementation, his post-discharge serum calcium fluctuated significantly, requiring close monitoring and frequent dose adjustments. Denosumab's unique antiresorptive properties yield fewer SREs. The trade-off is increased hypocalcemia risk, which may be severe and require aggressive, prolonged supplementation and monitoring.

Acute vitamin D intoxication in a child.

We present the unique case of a previously healthy, 2-year-old boy with resistant hypercalcemia and hypertension resulting from an unintentional overdose with an imported vitamin D supplement. The patient presented initially to the emergency department with colic and constipation and was discharged after a benign physical examination. The symptoms persisted and, on the second visit, the patient was found to have a serum calcium level of 14.4 mg/dL. Despite therapy with intravenously administered 5% dextrose solution at one-half normal strength, furosemide, calcitonin, and hydrocortisone, the calcium concentration increased to 15.0 mg/dL on the second hospital day and did not decrease until the fourth hospital day, when it fell to 13.9 mg/dL. The vitamin D concentration peaked at 470 ng/mL on hospital day 3. With additional questioning, the mother revealed that she had been giving her son a daily dose of 1 ampule of Raquiferol, an imported vitamin D supplement, instead of the recommended 2 drops per day. Each ampule contained 600,000 IU of vitamin D; therefore, the boy received a total of 2,400,000 IU over 4 days. The patient's hypercalcemia persisted for 14 days and was complicated by persistent hypertension. No renal, cardiac, or neurologic complications were noted. At discharge, the vitamin D concentration was still elevated at 389 ng/mL and the total calcium level had decreased to 11 mg/dL. The boy made a complete clinical recovery. This case highlights the need for caution when using imported and/or unregulated medicines, as well as the dangers of parental dosing errors.

Ischemic stroke associated with use of an ephedra-free dietary supplement containing synephrine.

In response to concerns regarding the safety of ephedra-containing dietary supplements, manufacturers have marketed "ephedra-free" products. Many of these contain synephrine, a sympathomimetic amine from the plant Citrus aurantium. Synephrine is structurally similar to ephedrine and has vasoconstrictor properties. We describe a 38-year-old patient with ischemic stroke associated with an ephedra-free dietary supplement containing synephrine and caffeine. The patient presented with memory loss and unsteady gait after taking 1 or 2 capsules per day of a dietary supplement (Stacker 2 Ephedra-Free) for 1 week. He had no notable medical history or major atherosclerotic risk factors and took no other medications. Physical examination showed a mildly ataxic gait and substantial Impairment of both concentration and memory. Computed tomography and magnetic resonance Imaging of the brain showed subacute infarctions in the left thalamus and left cerebellum in the distribution of the vertebrobasilar circulation. Other causes of ischemic stroke were evaluated, and findings were unremarkable; a vasospastic origin was considered most likely. The patient was discharged with nearly complete resolution of symptoms. Synephrine, a sympathomimetic amine related to ephedrine, may be associated with Ischemic stroke. Consumers and clinicians need to be Informed about the potential risks of ephedra-free products.

Exchange transfusion in severe infant salicylism.

We used exchange transfusion as an alternative to hemodialysis in an infant with severe salicylism. A 4-mo old, 5 kg male was presented to a local hospital with acute vomiting, tachypnea, hyperpnea and intermittent agitation and lethargy. Shortly after a generalized tonic-clonic seizure he passed several tablets in his stool. Salicylate (ASA) level was 85 mg/dL. He was transferred to our institution for further management: i.v. fluids, activated charcoal, whole bowel irrigation and supplementation with sodium bicarbonate, potassium and calcium. The patient's mental status and gas exchange deteriorated and he was intubated. Despite large amounts of sodium bicarbonate and potassium, severe hypokalemia, anion gap metabolic acidosis and aciduria persisted for 10 h. The small size of the infant precluded use of hemodialysis. An exchange transfusion using 180 mL/kg packed red blood cells reconstituted in fresh frozen plasma was performed. The pre-exchange transfusion ASA level was 70.1 mg/dL; the post-exchange transfusion ASA level was 34.4 mg/dL. There was rebound elevation of ASA to 35.2 mg/dL at 6 h post-exchange transfusion. The 18, 36 and 48 h post-exchange transfusion ASA levels were 20.2, 6.8 and < 2 mg/dL respectively. The ASA level dropped 17.6% before, 41.9% in 8.5 h during, and 40.5% by 48 h after the exchange transfusion. There were no complications. The patient recovered completely to his pre-morbid state. Double volume exchange transfusion was used safely as an effective alternative to hemodialysis in this case of severe infant salicylate poisoning.