Morrisons One-A-Night Sleep Aid (Diphenhydramine Hydrochloride)

Diphenhydramine Hydrochloride is used primarily for conditions involving histamine‑mediated symptoms and for short‑term sleep disturbances.

• Short‑term insomnia: helps initiate and maintain sleep during the night.
• Allergic rhinitis: relieves nasal itching, sneezing and watery discharge.
• Motion sickness: reduces nausea and vomiting associated with travel.
• Urticaria (hives): eases itching and skin rash.
• Common cold symptoms: alleviates sneezing and watery eyes.

• Diphenhydramine Hydrochloride acts as a competitive antagonist at histamine H1 receptors in the central nervous system and peripheral tissues. By blocking H1‑mediated signaling, it prevents the wake‑promoting effects of endogenous histamine, producing sedation. The molecule also exhibits anticholinergic activity by inhibiting muscarinic acetylcholine receptors, contributing to its sedative and drying effects. These actions together lower neuronal excitability, facilitating sleep onset.

Diphenhydramine Hydrochloride may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Drowsiness: feeling of sleepiness or reduced alertness.
• Dry mouth: decreased salivary secretion causing thirst.
• Dizziness: sensation of light‑headedness or imbalance.
• Blurred vision: temporary loss of visual clarity.
• Constipation: slowed gastrointestinal motility.
• Urinary retention: difficulty initiating urination.

Serious or Rare Side Effects

• Cardiac arrhythmia: irregular heart rhythm that may require medical attention.
• Anaphylaxis: severe allergic reaction with breathing difficulty and swelling.
• Hallucinations: visual or auditory disturbances not based in reality.
• Seizures: convulsive episodes that need urgent care.
• Angle‑closure glaucoma: sudden eye pain and visual loss.

When using Diphenhydramine Hydrochloride, certain precautions should be observed to minimize risk.

• Avoid alcohol: may intensify sedation and respiratory depression.
• Do not operate machinery: impaired coordination can increase accident risk.
• Use caution in elderly: heightened susceptibility to anticholinergic effects and confusion.
• Avoid use in narrow‑angle glaucoma: drug can increase intra‑ocular pressure.
• Store at ambient temperature: keep in the original pack, protect from moisture.

Diphenhydramine Hydrochloride can interact with several medicines, altering its sedative or anticholinergic profile.

Major Interactions (Avoid)

• Alcohol: additive central nervous system depression leading to excessive drowsiness.
• Opioids: combined use may cause profound sedation and respiratory depression.
• Other antihistamines: increased anticholinergic burden and heightened sedation.

Moderate Interactions (Monitor Closely)

• Benzodiazepines and barbiturates: may enhance drowsiness; dose adjustment may be needed.
• Anticholinergic drugs (e.g., atropine): risk of exaggerated anticholinergic effects such as dry mouth and urinary retention.
• MAO inhibitors: potential potentiation of antihistaminic effects, requiring clinical monitoring.