Lergigan Mite (Promethazine Hydrochloride)

Promethazine is used to manage conditions related to histamine‑mediated allergic responses and nausea.

• Allergic rhinitis: relief of nasal congestion, itching, sneezing and watery discharge.
• Urticaria (hives): reduction of itching and rash.
• Motion sickness: prevention of dizziness, vomiting and nausea associated with travel.
• Nausea and vomiting: control of symptoms from postoperative, chemotherapy or other causes.
• Pre‑operative sedation: calming anxiety and inducing sedation before surgical procedures.

• Promethazine acts as a competitive antagonist at peripheral H1 histamine receptors, blocking the action of histamine that causes allergic symptoms. It also exhibits anticholinergic, anti‑dopaminergic and anti‑serotonergic activity, which contributes to its antiemetic and sedative properties. By inhibiting central vestibular pathways and the chemoreceptor trigger zone, it reduces nausea, vomiting and induces drowsiness.

Promethazine 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 salivation leading to a dry sensation.
• Dizziness: light‑headedness or unsteady feeling.
• Blurred vision: temporary difficulty focusing.
• Constipation: reduced bowel movements.
• Nausea: mild stomach upset.

Serious or Rare Side Effects

• Severe allergic reaction: rash, itching, swelling, or difficulty breathing.
• Extrapyramidal symptoms: muscle rigidity, tremor, or involuntary movements.
• Respiratory depression: slowed or shallow breathing.
• Cardiac arrhythmias: irregular heart rhythm, especially in high doses.

When prescribing promethazine, clinicians should consider several safety measures.

• Assess patient history: evaluate for asthma, COPD or other respiratory disorders.
• Avoid use in children under two: risk of severe respiratory depression.
• Caution in elderly: increased sensitivity to sedation and anticholinergic effects.
• Monitor for CNS depression: avoid operating machinery or driving while impaired.
• Review concomitant medications: especially other CNS depressants or anticholinergics.
• Store at below 25°C: keep in original packaging, protect from moisture and direct sunlight.

Promethazine can interact with other medicines, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Alcohol: additive CNS depression leading to profound sedation.
• Opioids: increased risk of respiratory depression and profound sedation.
• Anticholinergic drugs: heightened anticholinergic burden causing confusion, urinary retention.

Moderate Interactions (Monitor Closely)

• CNS depressants (benzodiazepines, barbiturates): may enhance drowsiness.
• MAO inhibitors: potential for exaggerated hypotensive effects.
• Antihypertensive agents: possible additive blood pressure lowering.
• Antidepressants (tricyclics): increased anticholinergic side effects.