Feeling dizzy, nauseous, or having allergy attacks? Promethazine can help you clear all those in minutes to help you back on your feet. However, some claim to feel certain symptoms like sleepiness or drowsiness. Is there a truth to it? Does promethazine make you tired? Read on to find out more: 

What Does Promethazine Do?

Promethazine is a medication used to manage and treat allergic conditions, motion sickness, sedation, and pre/post-surgery pain, nausea, vomiting, and anxiety. It also treats allergy symptoms such as rash, itching, and runny nose and may also be used to treat a runny nose due to the common cold. 

Promethazine comes in various forms, such as an oral tablet, an oral solution, an injectable solution, and a rectal suppository. Its oral tablet is only available as a generic drug, which usually costs less than brand-name versions.

A derivative of phenothiazine, promethazine has antihistamine properties, which block a naturally-occurring substance called histamine that the body makes during an allergic reaction. Its effects, as mentioned above, such as anti-nausea, calming, and pain relief, may work by affecting other natural substances and acting directly on certain brain parts.

This drug may be used as part of combination therapy for certain conditions, so you may need to take it together with other medications.

Does Promethazine Make You Tired & Sleepy? – Side Effects

Does promethazine make you sleepy? – Yes, it does! Here’s how it works:

Since it relieves the symptoms of allergies, promethazine is an antihistamine medicine known for its sedative properties, so it’s more likely to make you sleepy than other antihistamines. Studies show that it helps when you have sleeping problems like insomnia or when a cough, cold, or itching keeps you up at night. Similarly, it can also ease tension and anxiety. 

The sedative effects of promethazine will start to kick in around 20 minutes after ingesting it and may last for up to 12 hours, which is why people usually take the medication at night. If you’re taking it for a cough or cold, allergies, or nausea, your symptoms should improve within 20 minutes.

So it may be a downside for those taking promethazine during the day for their allergies since it can disrupt their work or study. Avoid doing activities that require full concentration, like driving or operating heavy machinery. One study suggests that drinking alcohol with promethazine can also exacerbate drowsiness and induce delirium

Other Side Effects

Aside from drowsiness or sleepiness, the more common side effects that can occur with promethazine include:

  • Breathing problems
  • Ringing in the ears
  • Double vision
  • Nervousness
  • Dry mouth
  • Changes in blood pressure
  • Allergic skin reactions

Rarer, more severe side effects also occur. Consult your doctor immediately if you’re experiencing the following:

  • Confusion/agitation, 
  • Hallucinations/delirium
  • Nightmares
  • Seizures
  • Fast or slow heartbeats;
  • Jaundice 
  • Easy bruising 
  • Frequent bleeding (nosebleed, bleeding gums)
  • Uncontrolled muscle movements in the face
  • Sudden weakness or ill feeling
  • Red or swollen gums
  • Trouble swallowing
  • Severe nervous system reaction — stiffening of the muscles, high fever, profuse sweating, tremors, and presyncope (feeling faint, like you might pass out)

Oral promethazine is also known to affect blood sugar/blood pressure levels. If you have diabetes, taking promethazine could interfere with blood glucose control and reduce the effectiveness of medications like metFORMIN and others.

In case you’re experiencing any other side effects while taking promethazine, seek immediate medical attention. Your doctor may recommend another medication for your condition or to relieve side effects.


The following medications/drugs have been found to interact with promethazine, each with varying levels of interaction:

  • Ambien (zolpidem) (Moderate)
  • Benadryl (diphenhydramine) (Moderate)
  • Cymbalta (duloxetine) (Moderate)
  • Flexeril (cyclobenzaprine) (Moderate)
  • Lexapro (escitalopram) (Major)
  • Lyrica (pregabalin) (Moderate)
  • Nexium (esomeprazole)
  • Norco (acetaminophen / hydrocodone) (Moderate)
  • ProAir HFA (albuterol) (Moderate)
  • Protonix (pantoprazole)
  • Singulair (montelukast)
  • Synthroid (levothyroxine)
  • Topamax (topiramate) (Major)
  • Tylenol (acetaminophen)
  • Vitamin B12 (cyanocobalamin)
  • Vitamin C (ascorbic acid)
  • Vitamin D3 (cholecalciferol)
  • Xanax (alprazolam) (Moderate)
  • Zofran (ondansetron) (Moderate)
  • Zyrtec (cetirizine) (Moderate)

Mixing medications like promethazine with other drugs, foods, or supplements can result in unwanted side effects and diminish efficacy. 

Best Time To Take Promethazine

Take this medication by mouth with or without food as directed by your doctor, usually 2 to 4 times daily. If you’re taking promethazine for motion sickness, you should take it 30 to 60 minutes before beginning travel. For allergies, this medication may be taken once a day before bedtime to avoid being drowsy during the day. 

When used before surgery, promethazine can either be taken the night before or right before the scheduled procedure and may be continued afterward as prescribed. If you are using the liquid form of this medication, carefully measure the dose using a special measuring device/spoon. Using a household spoon may not get you an accurate dose.

The dosage is based on your age, medical condition, and response to treatment. In children, the dosage may also be based on weight. Do not increase your dose or take this medication more often than directed.

If you miss a dose, take it as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up for the missed dose.


Promethazine is a medication to relieve allergy symptoms, motion sickness, and nausea/vomiting before and after surgery. Being an antihistamine, it can cause a mild sedative effect which can help with sleeping troubles. However, it may be inconvenient for those who want to take it solely to relieve allergies.

Other side effects may occur occasionally. Talk with your doctor or pharmacist if they’re more severe or won’t go away. It’s also recommended to consult your doctor before taking promethazine to rule out possible health risks. 

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