Pharmacokinetics, Safety, and Tolerability Following Single and Multiple Doses of Pibrentasvir in a First-in-Human Study.

This first-in-human dose-ascending study investigated pharmacokinetics, safety, and tolerability of pibrentasvir following single and multiple doses in healthy volunteers. Additionally, the effects of food and ritonavir on pibrentasvir were assessed in a crossover study design. The starting dose of pibrentasvir was selected based on the no-observed-adverse-effect-level exposure from preclinical studies. Dose escalations of subsequent cohorts were dependent on reviews of the safety, tolerability, and pharmacokinetic data from previous dose cohorts. Pibrentasvir exposures increased in a greater than dose-proportional manner across the 1.5- to 120-mg dose range and became linear across the 120- to 600-mg dose range. Following multiple dosing, pibrentasvir steady state was attained by day 5 with an accumulation ratio of 25% to 35%. Pibrentasvir harmonic mean terminal half-life ranged from 20 to 22 hours. Food had minimal effect (<14%) on pibrentasvir bioavailability, but ritonavir increased pibrentasvir peak concentration and area under the concentration-time curve by 60% and 89%, respectively. All adverse events were assessed by the investigator as mild, and no clinically significant vital signs, electrocardiogram, or clinical laboratory values were observed. The pharmacokinetic results from this study support once-daily dosing and administration of pibrentasvir without regard to food. A maximum tolerated dose was not attained in the single- and multiple-ascending-dose assessments for pibrentasvir.

Pharmacokinetics, Safety, and Tolerability of Single and Multiple Doses of ABT-493: A First-In-Human Study.

ABT-493 is a hepatitis C virus nonstructural protein 3/4A protease inhibitor with pangenotypic antiviral activity. This study investigated the pharmacokinetics, safety, and tolerability of single and multiple ascending doses of ABT-493 and the effect of food and ritonavir coadministration on ABT-493 pharmacokinetics in healthy adults. In the blinded, randomized, placebo-controlled phase 1 single- and multiple-dose portions of the study, ABT-493 25-800 mg were evaluated as single doses, and 200, 400, and 800 mg were evaluated as multiple doses. The effect of food and ritonavir was assessed in a crossover unblinded fashion. ABT-493 pharmacokinetic parameters were estimated using noncompartmental methods. ABT-493 25-800 mg showed a greater than dose-proportional increase in exposures. Minimal accumulation (≤15%) was observed after ABT-493 200- and 400-mg multiple dosing; higher accumulations (approximately 80%) were observed after the 800-mg dose. ABT-493 harmonic mean half-life was 6-9 hours. Food had a minimal effect on ABT-493 exposures. All adverse events were assessed by the investigator as mild to moderate in severity, no serious adverse events were reported, and no subjects discontinued from the study. No clinically significant laboratory tests, vital signs, or electrocardiogram values were reported. A maximum tolerated dose was not reached.

Sildenafil citrate ingestion and prolonged priapism and tachycardia in a pediatric patient.

INTRODUCTION: Little is known about the toxicity of sildenafil overdose in the pediatric population. We present a case of prolonged priapism and tachycardia due to unintentional sildenafil overdose in a child. CASE REPORT: A 19-month-old male ingested up to six 50 mg Viagra tablets 45 minutes prior to presentation at the emergency department. Initial vital signs included temperature 98.2 degrees F, blood pressure 90/58 mmHg, heart rate 140, respirations 20, and oxygen saturation of 100% on room air. The child weighed 10.4 kg. Physical exam revealed a happy, smiling, laughing toddler who was cooperative with all aspects of his exam. He had mild facial flushing and an erect penis which was normal in color and had a capillary refill of two seconds. Precordial palpation did not show evidence of increase dynamic force, his heart sounds were regular, and no ectopy was noted. His peripheral pulses were strong and regular in all four extremities. No gastrointestinal decontamination was performed. The patient was started on maintenance IV fluids and admitted to the pediatric floor for observation. The patient had a non-painful tumescent penis and mild tachycardia for about 24 hours post-ingestion. The child never had pain from the constant erection. Sildenafil concentration drawn approximately seven hours after ingestion was 3900 ng/ml (reporting limit 24 ng/ml) and N-desmethylsildenafil level was 1700 ng/ml (reporting limit 24 ng/ml). CONCLUSION: This case of pediatric sildenafil ingestion (up to 30 mg/kg) initially resulted in facial flushing and priapism. The child had asymptomatic tachycardia and prolonged priapism that persisted until hospital discharge approximately 24 hours after ingestion. The erection was non-painful and required no urologic intervention, most likely representing a high flow state. In this ingestion, only supportive care was required.

Mercury exposure and public health.

Mercury is a metal that is a liquid at room temperature. Mercury has a long and interesting history deriving from its use in medicine and industry, with the resultant toxicity produced. In high enough doses, all forms of mercury can produce toxicity. The most devastating tragedies related to mercury toxicity in recent history include Minamata Bay and Niagata, Japan in the 1950s, and Iraq in the 1970s. More recent mercury toxicity issues include the extreme toxicity of the dimethylmercury compound noted in 1998, the possible toxicity related to dental amalgams, and the disproved relationship between vaccines and autism related to the presence of the mercury-containing preservative, thimerosal.

Methylene blue.

Methylene blue finds its major utilization in toxicology in the treatment of methemoglobinemia at a dose of 1 to 2 mg/kg intravenously. By interacting with methemoglobin and the erythrocyte's enzyme systems to reduce back to hemoglobin, methylene blue is a generally safe drug with dose-related hemolytic effects. People with G-6-PD deficiency, along with patients exposed to aniline dyes and dapsone, may present with special risks in the treatment of methemoglobinemia.