Diclegis Side Effects: What to Expect and When to Call Your Doctor

Diclegis (doxylamine succinate 10 mg / pyridoxine hydrochloride 10 mg) is considered the safest prescription option for morning sickness — it holds FDA Pregnancy Category A status, meaning controlled studies have not shown harm to the fetus. But like all medications, it can cause side effects. Knowing what to expect can help you manage them better and recognize the rare situations where you should call your doctor.

The Most Common Side Effect: Drowsiness

Drowsiness (somnolence) is by far the most commonly reported side effect of Diclegis. The doxylamine component is an antihistamine with sedating properties, similar to some over-the-counter sleep aids. The sleepiness can be significant — the FDA label warns that it can be 'severe' in some patients.

How to manage it:

Take Diclegis at bedtime as directed — the drowsiness is purposefully timed to help you sleep through nighttime nausea.

Do NOT drive or operate machinery until you know how Diclegis affects you.

Avoid alcohol, which amplifies the sedating effect.

If the drowsiness is interfering significantly with daytime functioning, discuss dose timing with your OB/GYN.

Other Common Side Effects

Fatigue: General tiredness beyond typical pregnancy fatigue. This is related to the antihistamine effect and usually improves as your body adjusts.

Dry mouth: Antihistamines have anticholinergic properties that can cause a dry mouth sensation. Stay hydrated and use sugar-free hard candies or gum if needed.

Dizziness: Some patients experience lightheadedness, especially when standing quickly. Rise slowly from lying or sitting positions.

Serious Side Effects — Call Your Doctor If You Experience These

Serious adverse effects from Diclegis are rare, but call your doctor immediately if you experience:

Severe difficulty breathing, chest tightness, or swelling of the face/tongue: These may indicate a serious allergic reaction. Call 911 or go to the nearest emergency room.

Unusual confusion or extreme sedation: Some sedation is expected, but if you feel unable to be roused or are severely disoriented, contact your provider.

Eye pain or vision changes: Diclegis has anticholinergic properties that can increase intraocular pressure. If you have narrow-angle glaucoma or suddenly develop eye pain, notify your provider immediately.

Inability to urinate: Anticholinergic effects can occasionally cause urinary retention, especially in women with bladder neck obstruction. Notify your doctor if you have difficulty urinating.

Drug Interactions That Can Amplify Side Effects

Diclegis's sedating effects are dramatically increased when combined with:

Alcohol — avoid completely

Benzodiazepines (e.g., diazepam, lorazepam) — avoid if possible

Opioid pain medications — risk of severe respiratory depression

Sleep aids and muscle relaxers — additive CNS depression

MAO inhibitors (phenelzine, tranylcypromine) — contraindicated; can cause serious, life-threatening reactions

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A Note on Drug Screen Results

There have been reports of Diclegis (doxylamine succinate/pyridoxine) causing false positive urine drug screening tests for methadone, opiates, and PCP. If you are required to undergo urine drug testing while taking Diclegis, inform the testing personnel that you are taking this medication. Confirmatory testing will show the false positive.

The Bottom Line

Drowsiness is the main side effect most patients experience with Diclegis. Taken at bedtime, it often improves sleep while controlling nausea. Serious side effects are rare. For more information on what Diclegis does and how to take it correctly, see what is Diclegis? and our Diclegis drug interactions guide.