Lenil Antiprurito (Promethazine Hydrochloride)

• Promethazine is employed as a topical antihistamine to manage conditions involving histamine‑mediated skin irritation.
• Pruritus: Reduces itch intensity and duration associated with various dermatologic conditions.
• Allergic skin reactions: Alleviates redness, swelling, and discomfort caused by contact allergens.
• Insect bite irritation: Provides symptomatic relief from itching and inflammation following insect bites.

• Promethazine exerts its antipruritic effect by competitively antagonizing peripheral H1 histamine receptors, preventing histamine‑induced vasodilation and nerve stimulation. The molecule also possesses anticholinergic activity, which contributes to its sedative properties, and modestly blocks muscarinic and serotonergic sites, enhancing overall anti‑itch action when applied to the skin.

Topical promethazine may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Skin irritation: mild redness or burning at the application site.
• Dryness: localized skin dryness or flaking.
• Drowsiness: mild sedation when absorbed systemically.
• Headache: occasional mild headache.

Serious or Rare Side Effects

• Severe allergic reaction: hives, swelling, or anaphylaxis requiring immediate medical attention.
• Contact dermatitis: intense rash or blistering at the site of application.
• Cardiac arrhythmia: rare reports of irregular heartbeat, especially with extensive use.

• When using Lenil Antiprurito, consider the following safety measures to minimize risk.
• Avoid use on broken skin: apply only to intact epidermis to reduce systemic absorption.
• Limit exposure: do not exceed the prescribed area or frequency to prevent toxicity.
• Monitor for sedation: be cautious when operating machinery if systemic effects occur.
• Pregnancy and lactation: consult a healthcare professional before use, as safety data are limited.
• Store below 25°C: keep in the original container, protect from moisture and light.

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

Major Interactions (Avoid)

• Central nervous system depressants (e.g., benzodiazepines, opioids): may enhance sedation and respiratory depression.
• Monoamine oxidase inhibitors (MAOIs): concurrent use can increase the risk of hypertensive crisis.

Moderate Interactions (Monitor Closely)

• Anticholinergic drugs (e.g., diphenhydramine, atropine): additive anticholinergic effects may cause dry mouth, urinary retention.
• Alcohol: may intensify drowsiness and impair coordination.
• Other antihistamines: combined use can increase sedation without added benefit.