Common and Serious Promethazine Side Effects
Most Common Side Effects
The most frequently reported promethazine side effects are related to its sedating antihistamine properties. Drowsiness affects many users, particularly when first starting treatment or increasing doses. This sedating effect often diminishes as your body adjusts to the medication. Dry mouth occurs because promethazine blocks acetylcholine receptors, reducing saliva production. Other common effects include blurred vision, constipation, and mild dizziness upon standing.
Managing Everyday Side Effects
For drowsiness, avoid driving or operating machinery until you know how promethazine affects you. Take your dose at bedtime when using it for allergies to minimise daytime sedation. Combat dry mouth by sipping water regularly, chewing sugar-free gum, or using saliva substitutes. If constipation occurs, increase dietary fibre and fluid intake. EverydayMeds stocks both Phenergan 25mg tablets and Phenergan Elixir 5mg/5ml, allowing you to choose the most suitable formulation.
Serious Side Effects Requiring Medical Attention
Whilst rare, some promethazine side effects need immediate medical assessment. Contact your GP or call 111 if you experience severe confusion, particularly in elderly patients, as this may indicate anticholinergic toxicity. Rapid or irregular heartbeat, severe dizziness, or fainting spells warrant prompt evaluation. Yellowing of skin or eyes could indicate liver problems, though this is extremely uncommon with promethazine.
Age-Related Considerations
Elderly patients may be more susceptible to promethazine's anticholinergic effects, potentially experiencing confusion, urinary retention, or increased fall risk. Children might paradoxically become hyperactive rather than sedated. Pregnant women should only use promethazine under medical supervision, particularly in the third trimester.
When to Seek Help
Stop taking promethazine and seek emergency care if you develop signs of severe allergic reaction: swelling of face, lips, tongue, or throat, severe rash, or breathing difficulties. Contact your healthcare provider if side effects persist beyond the first few days of treatment or significantly impact your daily activities.
