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Diclegis vs. Phenergan

Head-to-head comparisons of medication uses, side effects, warnings, and more.

Key takeaways

Diclegis (doxylamine/pyridoxine) and Promethazine (Phenergan) are both antihistamines, but they are used for different purposes and have different mechanisms of action. Diclegis is specifically FDA-approved to treat morning sickness in pregnant women and combines doxylamine, an antihistamine, with pyridoxine, a form of vitamin B6. It is taken orally and is not suitable for severe cases of nausea and vomiting during pregnancy. Promethazine, on the other hand, is used to treat a variety of conditions including allergies, motion sickness, nausea, and vomiting, and it can be administered orally, as an injection, or as a suppository. Promethazine works by blocking histamine, dopamine, and acetylcholine, making it more versatile but also associated with a higher risk of side effects, such as constipation and potential breathing problems in children under 2 years old. While Diclegis is safe for use during the first trimester of pregnancy, Promethazine is only recommended for pregnant women if Diclegis or other first-choice options are ineffective. Both are available in generic forms.

Diclegis

(doxylamine / pyridoxine)

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Promethazine

 

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Summary for Diclegis

Prescription only

Diclegis (doxylamine / pyridoxine) helps treat morning sickness, or nausea and vomiting that people experience during pregnancy. It's typically taken when changing your diet or avoiding nausea triggers isn't enough. This medication contains an antihistamine called doxylamine and a dietary supplement called pyridoxine (also known as vitamin B6). The dosage starts at 2 tablets taken by mouth at bedtime, but it can be adjusted if you need more relief. A common side effect is sleepiness. This medication has a brand-name and generic version.

Indications for Diclegis

  • Morning sickness (nausea and vomiting during pregnancy) when non-medication options haven't provided enough relief

Pros and Cons for Diclegis

Pros

  • One of the few medications that's FDA approved for morning sickness during pregnancy
  • Combines two medications into one tablet for convenience
  • Dose can be adjusted based on response

Cons

  • Dose ranges from 2 to 4 tablets per day, depending on your needs
  • Not for severe nausea and vomiting during pregnancy (hyperemesis gravidarum)
  • Not known whether it works well or is safe for people under 18 years old

Common Side Effects for Diclegis

  • Sleepiness (14%)

Warnings for Diclegis

  • Sleepiness
  • Worsening of certain other medical conditions

Summary for Phenergan

Prescription only

Promethazine is a prescription medication with many uses, such as treatment or prevention of nausea, motion sickness, and allergy symptoms. Promethazine works by blocking several chemicals, including histamine, dopamine, and acetylcholine. It comes as tablets, an oral solution, rectal suppositories, and an injection. The dose of promethazine and how often you take it depends on your age and what medical condition you're taking it to treat. But it shouldn't be given to children younger than 2 years of age since it can cause serious breathing problems. Common side effects include sleepiness and dizziness.

Indications for Phenergan

  • Runny nose, watery eyes, and other symptoms of allergies
  • Runny or stuffy nose that isn't caused by allergies
  • Rash, swelling, anaphylaxis, and other symptoms of an allergic reaction
  • Dermographism
  • Treatment or prevention of nausea and vomiting before and after surgery
  • Treatment or prevention of motion sickness
  • Treatment of pain along with other pain medications after surgery
  • Help to relax your body and produce a light sleep, particularly before a procedure

Pros and Cons for Phenergan

Pros

  • Available as a lower-cost generic
  • Available in different formulations, such as a tablet, syrup, and injection
  • Starts working within 20 minutes

Cons

  • Can't be taken by children under 2 years old because risk of serious breathing problem
  • Higher risk of side effects in older adults
  • Can cause sleepiness

Common Side Effects for Phenergan

  • Feeling drowsy or tired
  • Dizziness
  • Confusion
  • Dry mouth
  • Nervousness
  • Blurry vision

The following side effects are those additionally reported with promethazine injection at the injection site:

  • Burning
  • Pain
  • Rash
  • Swelling

Warnings for Phenergan

  • Potentially life-threatening slow breathing (respiratory depression)
  • Serious tissue injury (Injection only)
  • Excessive sleepiness
  • Worsening of certain health problems
  • Seizures
  • Higher risk of infection (from low white blood cell count)
  • Risk of serious nerve problems (neuroleptic malignant syndrome)
  • Uncontrollable body movements

Prices with our coupons for Diclegis vs. Phenergan

Price Card Drug Icon
Doxylamine/Pyridoxine60 tablets / 10mg/10mg
$55.41$106.95
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Price Card Drug Icon
Promethazine30 tablets / 25mg
$10.20$21.72
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