What is Hydroxyzine?
Hydroxyzine is a first-generation antihistamine available by prescription under brand names like Atarax and Vistaril [1.3.1, 1.7.7]. It is FDA-approved for several conditions, including:
- Anxiety and Tension: It's used for short-term management of anxiety and tension, often producing a calming effect [1.7.1, 1.7.2]. Its mechanism involves suppressing activity in key subcortical areas of the central nervous system and acting on serotonin receptors [1.5.1, 1.5.4]. Unlike benzodiazepines, it is not considered habit-forming [1.3.4].
- Allergic Conditions: It effectively treats itching (pruritus) associated with conditions like chronic urticaria (hives), eczema, and contact dermatoses by blocking the body's histamine response [1.7.2, 1.7.7].
- Sedation: Due to its sedative properties, it can be used before or after general anesthesia to help patients relax or sleep [1.7.2].
Hydroxyzine works by blocking H1 histamine receptors in the brain and body [1.5.1]. This action prevents histamine from causing allergic symptoms. Its calming effect is also linked to its antagonist activity at serotonin 5-HT2A receptors [1.5.1]. The medication begins to work within 15 to 30 minutes of oral administration, with effects lasting four to six hours [1.5.6].
The Most Common Side Effects
The most frequently reported side effects of hydroxyzine stem from its sedative and anticholinergic properties [1.3.1, 1.5.6]. Patients commonly experience:
- Drowsiness and Sedation: This is the most common side effect, which often diminishes with continued use [1.3.3, 1.5.6].
- Dry Mouth: A classic anticholinergic effect [1.3.5].
- Headache: A possible side effect of many antihistamines [1.6.1].
- Dizziness or Confusion: Especially in older adults [1.3.8].
Is Diarrhea a Side Effect of Hydroxyzine?
Yes, diarrhea is a possible, though not common, side effect of hydroxyzine [1.2.1, 1.2.2]. Some sources list it among other reported adverse reactions [1.2.1]. It may occur due to gastrointestinal irritation from the medication [1.2.2].
However, it's important to note that constipation is a more frequently cited gastrointestinal side effect [1.4.4]. This is due to hydroxyzine's anticholinergic activity. Anticholinergic drugs work by blocking the neurotransmitter acetylcholine, which can slow down the movement of food through the intestines, leading to constipation [1.6.1].
In some cases, gastrointestinal symptoms like nausea, vomiting, and diarrhea can also be signs of serotonin syndrome, a rare but serious condition that can occur if hydroxyzine is taken with other medications that increase serotonin, such as SSRI antidepressants [1.2.4].
Comparing GI Side Effects: Hydroxyzine vs. Other Medications
| Medication | Type | Common GI Side Effects | Diarrhea | Constipation |
|---|---|---|---|---|
| Hydroxyzine (Vistaril, Atarax) | 1st-Gen Antihistamine | Dry mouth, nausea, stomach distress [1.3.3, 1.4.5] | Less Common [1.2.2] | More Common [1.4.4] |
| Diphenhydramine (Benadryl) | 1st-Gen Antihistamine | Dry mouth, constipation, nausea | Possible | Common |
| Loratadine (Claritin) | 2nd-Gen Antihistamine | Headache, dry mouth | Possible | Less Common |
| Sertraline (Zoloft) | SSRI Antidepressant | Nausea, diarrhea, constipation, loss of appetite [1.2.6] | Common [1.2.6] | Common [1.2.6] |
| Buspirone | Anxiolytic | Nausea, dry mouth [1.2.6] | Possible [1.2.6] | Less Common |
Managing Hydroxyzine Side Effects
If you experience mild side effects from hydroxyzine, several home-care strategies may help [1.6.1, 1.6.2]:
- For Diarrhea: Stay hydrated by drinking plenty of water and clear liquids. Eat bland foods and avoid spicy or greasy meals. Talk to your doctor before using anti-diarrhea medications [1.2.2].
- For Constipation: Increase your intake of fluids and dietary fiber. If that doesn't help, ask your pharmacist about over-the-counter laxatives or stool softeners [1.6.1].
- For Dry Mouth: Chew sugar-free gum, suck on ice chips or sugar-free candy, or use an over-the-counter saliva substitute [1.7.5].
- For Drowsiness: Take hydroxyzine at bedtime if you are on a once-daily dose. Avoid driving or operating heavy machinery until you know how the medication affects you. Do not consume alcohol, as it can increase drowsiness [1.6.1, 1.6.7].
When to Contact a Healthcare Provider
You should contact your doctor if side effects are severe, persist, or worsen. Seek immediate medical attention if you experience signs of a serious reaction, which can include [1.3.5, 1.3.8]:
- Fast or pounding heartbeats, or a feeling of fainting [1.3.5].
- Headache with chest pain [1.3.5].
- Seizures or convulsions [1.3.8].
- Unintentional trembling or shaking movements [1.3.8].
- A severe skin reaction, such as a rash that spreads and causes blistering or pus [1.3.5, 1.3.8].
- Signs of an allergic reaction like hives, difficulty breathing, or swelling of the face, lips, or tongue [1.3.5].
Conclusion
While diarrhea is a recognized side effect of hydroxyzine, it is reported less frequently than other gastrointestinal issues like constipation and dry mouth [1.2.1, 1.4.4]. The medication's primary side effects, such as drowsiness and dry mouth, are due to its antihistaminic and anticholinergic properties [1.3.1]. Most mild side effects are manageable and may subside as your body adjusts to the medication [1.3.3]. However, it is crucial to communicate with your healthcare provider about any persistent or severe symptoms and to seek immediate medical help for any signs of a serious reaction.
For more detailed information, consult a trusted medical source like MedlinePlus [1.3.8].
