Serum concentrations in three children with unintentional tetrahydrozoline overdose
ABSTRACT Major symptoms can occur from tetrahydrozoline (THZ) overdoses in young children, requiring intensive care management. We report three cases that presented with CNS depression and cardiovascular effects where serum concentrations were performed.
Case 1 ingested an unknown amount of eye drops containing THZ, resulting in altered mental status, bradycardia, hypothermia, and hypotension. Cases 2 and 3 ingested 7.5 mL of eye drops containing THZ. Case 2 presented to the emergency department (ED) without symptoms but became lethargic and bradycardic 90 min after ingestion. By contrast, Case 3 became lethargic 15 min after ingestion and required intubation on arrival to the ED. All children were admitted to ICU for observation and improved within 24 h of ingestion. Urine obtained for drug screening was positive for THZ. Blood was obtained to assess level using gas-chromatography mass-spectrometry (GC-MS). CASE DISCUSSION: Case 1 had plasma levels of 51.4 and 23.6 ng/mL at 7 and 12 h, respectively, after ingestion, revealing a half-life of 4.4 h. Numerous case reports have been published documenting the dangers of ingesting these topical over-the-counter (OTC) products. However, human PK data are not available to help in our understanding of THZ toxicokinetics and disposition in humans after ingestion.
We report three pediatric cases after ingestion of THZ where plasma concentrations were obtained with a calculated half-life of 4.4 h in one case.
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ABSTRACT: Introduction. The alpha-2 adrenergic (AA-2) receptor agonists and imidazolines are common exposures in the American Association of Poison Control Centers (AAPCC) National Poison Data System (NPDS). Although the interaction between the AA-2 receptor and imidazoline receptors has been extensively studied, it largely remains unknown to health-care professionals. This review describes these interactions and mechanisms by which agonists affect physiologic responses binding to these receptors. Methods. Papers published in English from 1960 to 2013 were retrieved from PubMed. A total of 323 original articles were identified and 173 were included. Background. The toxicity associated with clonidine (e.g., bradycardia, miosis, and hypotension) is largely assumed to be secondary to the functional overlap of the AA-2 receptors and the mu receptors. However, the effects at the AA-2 receptor could not fully account for these symptoms. Subsequently, clonidine was found to produce its pharmacologic effect in the central nervous system (CNS) by interaction not only with the AA-2 receptor but also on selective imidazoline receptors. Imidazoline receptors. Since their discovery, three distinct classes of imidazoline receptors, also known as imidazoline binding sites or imidazoline/guanidinium receptive sites, have been characterized. Imidazoline-1 (I-1) receptors are involved in the hypotensive activity of clonidine and related compounds supporting the idea that the I-1 receptors are upstream from the AA-2 receptor and work in tandem for its effect on blood pressure. Additionally, stimulation of N-type Calcium-2 channels, G-protein inwardly rectifying potassium channel, adenosine receptors, phosphatidyl-choline-specific phospholipase C, and nicotinic receptors have been implicated to be involved. Previous studies have shown that I-1 receptors may also be involved in other physiologic responses beyond cardiac function. Imidazoline-2 (I-2) receptors interact with monoamine oxidase A and monoamine oxidase B leading to research that has focused on the effect of I-2 receptors and depression and the suggestion of a possible antidepressant action of the imidazolines. I-2 receptor ligands may have substantial antinociceptive activity and work synergistically with opioids in acute pain. Imidazoline-3 (I-3) receptors are located on the pancreatic β-cells and modulate glucose homeostasis. Imidazoline ligands. Four endogenous compounds have been found to bind and include clonidine-displacing substance, agmatine, harmane, and imidazole acetic acid. Significant interest in developing new agents with higher selectivity and affinity for I-1 receptors has resulted. Toxicology. Alpha-2 adrenoceptor and imidazoline receptor agonists such as clonidine and tetrahydrozoline are common ingestions reported to poison control centers. The most common toxic effects of clonidine are similar to those of the over-the-counter imidazolines and include CNS depression, bradycardia, hypotension, respiratory depression, miosis, hypothermia, and hypertension (early and transient). Based on their structure and subsequent studies, imidazoline receptors seem to be the primary binding site for these chemicals. Case reports typically illustrate rapid onset of action with serious side effects following ingestion of relatively small amounts. These agents have been reportedly used in drug-assisted sexual assaults. Conclusion. Much of the toxicity associated with drugs such as clonidine, guanfacine, and tetrahydrozoline are due to their binding to imidazoline receptors. Knowledge of the imidazoline receptors may lead to new therapeutic agents and inform management of patients with imidazoline overdose.Clinical Toxicology 03/2014; 52(5). DOI:10.3109/15563650.2014.898770 · 3.12 Impact Factor
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ABSTRACT: BACKGROUND: Oxymetazoline nasal spray is not FDA approved for use in children less than 6 years; however, its safety and efficacy are widely accepted, and it is in widespread use in children prior to procedures that may lead to epistaxis. We report a case of intraoperative oxymetazoline toxicity in a 4-year-old boy that led to a hypertensive crisis. While examining the possible causes for this problem, we became aware that the method of drug delivery led to an unanticipated overdose. The position in which the bottle is held causes pronounced variation in the quantity of oxymetazoline dispensed. METHODS: To examine the impact that bottle position has on the volume delivered, we measured the volume of oxymetazoline dispensed with the bottle in the upright and inverted position. We also measured the volume of a drop of oxymetazoline dispensed from the bottle. Because an additional source of oxymetazoline exposure is from packing the nares with surgical pledgets, we analyzed the volume of oxymetazoline absorbed by each pledget. RESULTS: Squeezing the bottle in the upright position results in a fine spray of fluid that averaged 28.9 ± 6.8 μl and was largely independent of effort. This volume is nearly identical to the measured volume of a drop of oxymetazoline, which was 30 μl. However, squeezing the bottle in the inverted position resulted in a steady stream of fluid, and the volume administered was completely effort dependent. Multiple tests in the inverted position demonstrated an average volume of 1037 ± 527 μl, with a range of 473-2196 μl. Lastly, the volume of oxymetazoline absorbed by each surgical pledget was 1511 ± 184 μl. DISCUSSION: Our testing indicates that bottle position during oxymetazoline administration can cause up to a 75-fold increase in intended drug administration.Pediatric Anesthesia 05/2013; 23(10). DOI:10.1111/pan.12192 · 1.74 Impact Factor
Journal of medical toxicology: official journal of the American College of Medical Toxicology 04/2014; 10(4). DOI:10.1007/s13181-014-0400-9