Hydroxyzine is a prescription medication primarily used to manage symptoms of anxiety and to relieve itching caused by allergic conditions. It functions as a first-generation antihistamine with sedative properties. Like any medication, hydroxyzine carries a risk of toxicity when taken in excess, meaning an overdose is possible and can lead to serious, potentially life-threatening complications. Overdose effects occur due to the drug’s influence on the central nervous system and its impact on cardiac function, necessitating prompt medical attention if toxicity is suspected.
Understanding the Overdose Threshold
The point at which a hydroxyzine dose becomes toxic varies significantly among individuals. Toxicity is often reached when the amount consumed overwhelms the body’s ability to safely metabolize and clear the drug, leading to hypersedation and pronounced physiological effects. The presence of other substances that also depress the central nervous system dramatically lowers this threshold, making the combination extremely risky.
Consuming hydroxyzine alongside alcohol, opioids, or benzodiazepines can intensify the sedative effects, increasing the chances of profound drowsiness, respiratory depression, and even coma. This combined effect on the brain’s function is a major contributor to severe overdose cases, where the body’s protective reflexes begin to fail. Individuals with pre-existing health conditions face an inherently lower threshold for toxicity, even with smaller excessive doses.
Those with liver or kidney impairment may not be able to process and eliminate the drug effectively, causing high concentrations to build up in the bloodstream. A significant concern involves individuals with underlying heart conditions, as hydroxyzine can interfere with the heart’s electrical system. This interference is related to the drug’s ability to block certain potassium channels in cardiac cells, which can predispose a person to dangerous heart rhythm disturbances. High blood levels of the medication, such as those reached during an overdose, heighten this cardiac risk.
Recognizing the Signs of Toxicity
The symptoms of hydroxyzine toxicity arise mainly from its effects on the central nervous system (CNS) and the cardiovascular system. The most common sign of an overdose is profound hypersedation, which can range from extreme drowsiness and confusion to stupor or even a deep coma. In some instances, particularly in older adults or children, the CNS effects can manifest as agitation, hallucinations, and uncoordinated movements. Seizures are also a documented complication of severe hydroxyzine toxicity.
The drug also possesses anticholinergic properties, which can result in a specific set of physical symptoms. These effects include blurred vision, noticeably dilated pupils, and a severe sensation of dry mouth. Difficulty with urination, known as urinary retention, may also occur as a sign of toxicity. These symptoms reflect the drug’s influence on various involuntary bodily functions regulated by the nervous system.
The most serious danger in an overdose involves the heart, where hydroxyzine can disrupt normal rhythm and function. Individuals may experience a rapid heart rate, known as tachycardia, along with noticeable heart palpitations. Overdose can also lead to hypotension, a dangerous drop in blood pressure that can cause dizziness, fainting, or shock. Of particular concern is the potential for QT interval prolongation, which is an electrical delay in the heart’s cycle that can lead to a deadly arrhythmia called Torsade de Pointes.
Immediate Action and Medical Management
If an overdose of hydroxyzine is suspected, the first and most immediate action is to call emergency services or Poison Control. The national toll-free Poison Help hotline is available to provide expert guidance. It is important to provide medical personnel with as much information as possible, including the amount of medication taken, the time of ingestion, and any other substances consumed.
While awaiting professional help, the person should be kept awake if possible, and vomiting should not be induced unless specifically instructed to do so by a medical professional. Once in a medical setting, the treatment approach centers on supportive care, as there is no specific antidote available for hydroxyzine toxicity. The immediate goals are to maintain the person’s airway, ensure adequate breathing, and stabilize circulation.
Medical staff will continuously monitor the person’s vital signs, including blood pressure, respiratory rate, and oxygen saturation. Intensive cardiac monitoring, typically involving an electrocardiogram (ECG), is performed to watch for signs of QT prolongation or other dangerous arrhythmias. To limit the absorption of the drug from the stomach, activated charcoal may be administered if the ingestion was recent. Specific symptoms are treated as they arise, such as using intravenous fluids to manage low blood pressure or administering benzodiazepines to control seizures.