Xonvea

What doxylamine succinate / pyridoxine hydrochloride is and how it works

Xonvea contains two active substances: doxylamine succinate, which belongs to a group of medicines called antihistamines, and pyridoxine hydrochloride, another name for vitamin B6. It is used in pregnant women aged 18 years and older to help stop them feeling sick (nausea) and being sick (vomiting), when changes in diet or other non-medicine treatments have not worked. (1) (2)

Xonvea is indicated for the treatment of nausea and vomiting of pregnancy (NVP) in pregnant women aged 18 years or older who do not respond to conservative management (lifestyle and diet change). It should be taken as a daily prescription and not on an as-needed basis. Continued need should be reassessed as the pregnancy progresses. Xonvea is not indicated for use in children under 18 years of age.

Mechanism of action: how doxylamine succinate / pyridoxine hydrochloride works

Xonvea contains two active substances: doxylamine succinate, an antihistamine (ethanolamine-derivative), and pyridoxine hydrochloride, also known as vitamin B6. Doxylamine succinate has anticholinergic properties. Full pharmacological properties (section 5) were not quoted in the supplied research notes beyond the statement that section 5 of the SmPC is the pharmacological properties section; no further pharmacology detail can be stated. (1) (2)

What is Doxylamine succinate / pyridoxine hydrochloride used for?

Before taking doxylamine succinate / pyridoxine hydrochloride

Do not take / not appropriate for

• Do not take Xonvea if you are allergic (hypersensitive) to doxylamine succinate, other ethanolamine-derivative antihistamines (such as diphenhydramine), pyridoxine hydrochloride or any of the other ingredients of this medicine. (all patients) (1) (2)
• Do not take Xonvea if you are taking medicines for depression called monoamine oxidase inhibitors (MAOIs). Concomitant use with MAOIs is contraindicated. (all patients) (1) (2)

Tell your clinician about

• If you have ever had: asthma; increased eye pressure; an eye problem called narrow angle glaucoma; a stomach ulcer (stenosing peptic ulcer); a blockage in your gut between your stomach and small intestine (pyloroduodenal obstruction); or a blockage in your bladder (bladder-neck obstruction) - Xonvea has anticholinergic properties and should be used with caution in these patients.
• If you are taking cough or cold medicines, sleeping medicines or certain pain medicines (central nervous system depressants), because using any of these with Xonvea can make you feel very sleepy and this can make you fall over or cause other accidents.
• If you have been drinking alcohol. Use of Xonvea is not recommended if a woman is concurrently using central nervous system (CNS) depressants including alcohol.
• If you are taking any additional vitamin B, through your diet, from supplements or multivitamins - Xonvea contains pyridoxine hydrochloride, a vitamin B6 analogue, so additional levels from diet and vitamin B6 supplements should be assessed.
• If you are having a urine drug screen - Xonvea may show false positive results for methadone, opiates, and phencyclidine phosphate (PCP) when some test methods are used; a more specific confirmatory test can be performed.
• If you suffer from severe nausea and vomiting of pregnancy, a condition called hyperemesis gravidarum, you have to be treated by a specialist, because there is limited evidence in cases of hyperemesis gravidarum for the combination doxylamine/pyridoxine.
• If you cannot swallow Xonvea tablets whole, tell your doctor, pharmacist or nurse.
• If you are breastfeeding, or plan to breastfeed - a decision should be made with your doctor.
• This medicine contains the azo colouring agent Allura red AC aluminium lake (E 129), which may cause allergic reactions.

Doxylamine succinate / pyridoxine hydrochloride dosage and how to take it

• Always take this medicine exactly as your doctor, pharmacist or nurse has told you. Check with your doctor, pharmacist or nurse if you are not sure.
• Your doctor will start you on a low dose and possibly increase it - this will depend on how well the medicine works for you.
• Day 1: take 2 tablets by mouth at bedtime (recommended starting dose: total dose 20 mg doxylamine succinate / 20 mg pyridoxine hydrochloride).
• Day 2: take 2 tablets by mouth at bedtime. If your nausea and vomiting is better or controlled on Day 2, continue to take 2 tablets every night at bedtime; this will be your usual dose unless your doctor, pharmacist or nurse tells you otherwise.
• Day 3: if you still had nausea and vomiting on Day 2, take 1 tablet in the morning and 2 tablets at bedtime, by mouth.
• Day 4: if your nausea and vomiting was better or controlled on Day 3, continue to take 1 tablet in the morning and 2 tablets at bedtime by mouth each day; this will be your usual dose unless your doctor, pharmacist or nurse tells you otherwise.
• Day 4: if you still had nausea and vomiting on Day 3, take 1 tablet in the morning, 1 tablet in the mid-afternoon, and 2 tablets at bedtime, by mouth. This will be your usual dose unless your doctor, pharmacist or nurse tells you otherwise.
• The maximum recommended daily dose is 4 tablets (1 in the morning, 1 in the mid-afternoon and 2 at bedtime). Do not take more than 4 tablets each day.
• Xonvea should be taken on an empty stomach with a glass of water. A food-effect study has shown that the delay in onset of action may be further delayed, and a reduction in absorption may occur, when tablets are taken with food.
• Swallow the tablet whole with a glass of water. Do not crush, chew or split the tablets before swallowing, to preserve the effect of this medicine and the gastro-resistant properties.
• Xonvea should be taken as a daily prescription and not on an as needed basis.
• Continued need for Xonvea should be reassessed as the pregnancy progresses.
• Do not change the dose yourself; follow the schedule your doctor, pharmacist or nurse has told you.

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3)

Missed dose

Follow the exact product instructions and do not double a dose.

Overdose

Xonvea is a delayed-release formulation; therefore, signs and symptoms may not be apparent immediately. If you take more Xonvea than you should, seek medical attention promptly - talk to a doctor or go to a hospital straight away, even if you feel well, and take the medicine pack with you. Signs and symptoms of overdosage may include restlessness, dryness of mouth, dilated pupils, sleepiness, vertigo, mental confusion and tachycardia. At toxic doses, doxylamine exhibits anticholinergic effects, including seizures, rhabdomyolysis, acute renal failure and death. In the event of an overdose, management consists of activated charcoal, whole bowel irrigation and symptomatic treatment, in accordance with established treatment guidelines. Fatalities have been reported from doxylamine overdose in children; children appear to be at high risk for cardiorespiratory arrest and a toxic dose for children of more than 1.8 mg/kg has been reported. Let the clinician you see advise on whether to continue or stop, and on any further treatment. (1) (2)

Doxylamine succinate / pyridoxine hydrochloride side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them. Adverse event information is derived from clinical trials and worldwide post-marketing experience; the incidence of treatment-emergent adverse events was similar for both treatment and placebo groups. The most frequently reported adverse reaction (>=5% and exceeding the rate in placebo) was somnolence. Frequency of adverse reactions reported during post-marketing use cannot be determined as they are derived from spontaneous reports and are therefore qualified as 'not known'.

Serious warnings

Interactions

Pregnancy, breastfeeding, kidney/liver function, age

Monitoring

Before starting

• Confirm the patient is a pregnant woman aged 18 years or older with nausea and vomiting of pregnancy who has not responded to conservative management (lifestyle and diet change).
• Assess for hypersensitivity to doxylamine succinate, other ethanolamine-derivative antihistamines, pyridoxine hydrochloride or any excipients.
• Check for concomitant use of MAOIs (contraindicated) and of CNS depressants including alcohol, hypnotic sedatives and tranquilizers (not recommended).
• Assess additional vitamin B6 intake from diet and vitamin B6 supplements.
• Assess the conditions requiring caution due to anticholinergic properties: asthma, increased intraocular pressure, narrow angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction and bladder-neck obstruction.
• Confirm the patient can swallow the gastro-resistant tablets whole.
• Consider specialist referral if hyperemesis gravidarum is suspected, because evidence is limited in this population.

During treatment

• Reassess continued need for Xonvea as the pregnancy progresses.
• Reassess symptom control to determine whether the dose should be increased as per the day 1 to day 4 schedule, or whether the usual dose continues.
• Advise avoidance of driving, cycling and use of tools or machines while taking Xonvea until cleared by the healthcare provider.
• Reassess concurrent use of CNS depressants, alcohol and additional vitamin B6 intake.
• At the time of discontinuation, use a gradual tapering dose to prevent a sudden return of nausea and vomiting of pregnancy symptoms; the doctor will tell the patient how to stop the medicine slowly over time.

Storage

This medicine does not require any special storage conditions. Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date which is stated on the carton or blister after 'EXP'. The expiry date refers to the last day of that month. Do not throw away any medicines via wastewater or household waste; ask your pharmacist how to throw away medicines you no longer use.

Frequently asked questions

References

1. Xonvea 10 mg/10 mg gastro-resistant tablets — Summary of Product Characteristicselectronic Medicines Compendium (UK), Exeltis UK · United Kingdom · accessed 2026-10-13 · source 1
2. Xonvea 10 mg/10 mg gastro-resistant tablets — Package leaflet: Information for the userelectronic Medicines Compendium (UK), Exeltis UK · United Kingdom · accessed 2026-10-13 · source 2
3. DICLEGIS (doxylamine succinate and pyridoxine hydrochloride) delayed-release tablets — prescribing informationDailyMed, U.S. National Library of Medicine · United States · accessed 2026-10-13 · source 3

Brand names by country

Single-ingredient doxylamine succinate / pyridoxine hydrochloride names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries