From the Guidelines
Diphenhydramine syrup is primarily indicated for the temporary relief of allergy symptoms, including sneezing, runny nose, itchy eyes, nose, and throat, as well as for the management of urticaria (hives) and other allergic skin reactions, but its use in children under 6 years is not recommended without medical supervision due to potential toxicity 1.
Indications and Usage
The indications for diphenhydramine syrup include:
- Temporary relief of allergy symptoms such as sneezing, runny nose, itchy eyes, nose, and throat
- Management of urticaria (hives) and other allergic skin reactions
- Treatment of motion sickness
- Sleep aid for occasional insomnia
- Suppression of coughs due to minor throat and bronchial irritation
Dosage and Administration
The typical adult dose is 25-50 mg (10-20 ml of the 12.5 mg/5 ml syrup) every 4-6 hours, not exceeding 300 mg in 24 hours. For children 6-12 years old, the dose is typically 12.5-25 mg (5-10 ml) every 4-6 hours, not exceeding 150 mg daily.
Mechanism of Action
Diphenhydramine works by blocking histamine H1 receptors, thereby reducing allergic symptoms. It also has anticholinergic properties that contribute to its sedative effects and ability to reduce secretions.
Side Effects and Precautions
Patients should be aware that diphenhydramine can cause drowsiness, dry mouth, and blurred vision, so activities requiring mental alertness should be avoided. The medication should not be used in children under 6 years without medical supervision, and caution is advised in elderly patients who may be more sensitive to side effects 1. Additionally, diphenhydramine can be used as part of the treatment for anaphylaxis, with a dose of 1 to 2 mg/kg or 25 to 50 mg per dose (parenterally) 1, and for cyclic vomiting syndrome, with a dose of 12.5-25 mg every 4-6 hours during an episode 1.
From the Research
Indications for Diphenhydramine Syrup
The indications for diphenhydramine syrup, an antihistamine, can be summarized as follows:
- Relief of symptoms associated with upper respiratory tract infections, such as runny nose and sneezing 2
- Treatment of seasonal allergic rhinitis, including symptoms such as nasal congestion, sneezing, and runny nose 3
- Use as a sleep aid, due to its sedative effects 4, 5, 6
- Potential use in relieving symptoms of insomnia, particularly in older adults 4
Key Findings
Some key findings related to the use of diphenhydramine syrup include:
- Diphenhydramine has been shown to be effective in reducing symptoms of seasonal allergic rhinitis, including nasal congestion and sneezing 3
- The drug has a sedative effect, which can be beneficial for use as a sleep aid, but may also lead to next-day residual sedation 5
- Tolerance to the sedative effects of diphenhydramine can develop rapidly, within 3-4 days of administration 6
- Diphenhydramine may be more effective than other antihistamines, such as desloratadine, in relieving symptoms of seasonal allergic rhinitis 3