Critical Drug Interactions and Safety Warnings
Dangerous Medication Combinations
Several medication classes should never be combined with Phenergan 25mg tablets or elixir. MAOIs (monoamine oxidase inhibitors) represent the most serious interaction, potentially causing severe blood pressure changes. These include phenelzine, tranylcypromine, and moclobemide. Always inform your pharmacist about any antidepressants you're taking.
Central Nervous System Depressants
Combining Phenergan with other sedating substances dramatically increases drowsiness and respiratory depression risks. Avoid benzodiazepines (diazepam, lorazepam), sleeping tablets (zopiclone, zolpidem), opioid painkillers, and muscle relaxants. Even over-the-counter sleep aids containing diphenhydramine or doxylamine can cause dangerous sedation when combined with promethazine.
Anticholinergic Drug Interactions
Phenergan has strong anticholinergic effects, so combining it with similar medications can cause serious side effects including confusion, dry mouth, constipation, and urinary retention. Avoid tricyclic antidepressants (amitriptyline), antihistamines (chlorphenamine), motion sickness tablets containing hyoscine, and bladder medications like oxybutynin.
Alcohol and Lifestyle Considerations
Alcohol significantly amplifies Phenergan's sedating effects and should be completely avoided. Even small amounts can cause severe drowsiness, confusion, and dangerous falls. This applies to both the 25mg tablets and 5mg/5ml elixir formulations available through EverydayMeds. The interaction can last up to 24 hours after taking the medication.
Activities to Avoid
Never drive, operate machinery, or engage in activities requiring alertness whilst taking Phenergan. The medication can cause drowsiness for 8-12 hours after taking tablets, and the elixir formulation can have similar effects. Avoid climbing ladders, using power tools, or making important decisions whilst under the medication's influence.
Medical Conditions Requiring Caution
Certain health conditions make Phenergan potentially dangerous. Those with severe asthma, COPD, sleep apnoea, or breathing problems should avoid this medication entirely. Epilepsy, heart rhythm problems, enlarged prostate, glaucoma, and severe liver disease also contraindicate use. Always consult your GP or EverydayMeds pharmacist before starting treatment.
