What are the side effects of promethazine?

Taking promethazine may cause a variety of side effects, ranging from mild to serious. Typical side effects include:

  • lightheadedness
  • loss of coordination
  • blurred vision
  • hyperactivity
  • weight gain
  • anxiety
  • difficulty sleeping
  • constipation
  • unusually happy mood
  • stuffy nose
  • swelling in the hands and feet
  • tiredness
  • itching
  • impotence

More serious side effects include:

  • allergic reactions
  • fever
  • rash
  • agitation
  • flu-like symptoms
  • uncontrollable twitching
  • fever
  • muscle stiffness
  • joint swelling
  • neck contortions
  • hallucinations
  • confusion
  • decreased urination
  • sensitivity to light
  • chest pain
  • weak pulse
  • shallow breathing
  • irregular heartbeat
  • jaundice (yellow skin or eyes)
  • tongue hanging out of the mouth
  • difficulty swallowing

Seek medical attention immediately if you have any of these more serious side effects.

Based on information from, a free medication monitoring service, 44% of patients experience side effects while taking Promethazine (Phenergan). Some of the side effects reported by iGuard members include:

  • Drowsiness
  • Nausea/Vomiting
  • Dryness
  • Anxiety
  • Fatigue
  • Dizziness
  • Increased Appetite
Please follow up with your doctor or other healthcare provider if you are experiencing any symptoms that worsen or do not go away.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.