Doxylamine / Pyridoxine (Diclectin)

1. Health Canada Product Monograph — Doxylamine / Pyridoxine

• Doxylamine / Pyridoxine is used to manage nausea and vomiting of pregnancy and can be prescribed during any trimester.
• It is a delayed-release formulation intended for regular scheduled use rather than as-needed dosing, since it is designed to prevent symptoms rather than treat them after they start.

• Doxylamine / Pyridoxine is specifically intended for use during pregnancy, and extensive data from millions of pregnancies have not shown an increased risk of birth defects.
• Large studies analyzing outcomes after first-trimester use found no meaningful link between this combination and congenital malformations.
• Doxylamine / Pyridoxine can be used in any trimester of pregnancy under a doctor's guidance.

• Doxylamine / Pyridoxine is not recommended while breastfeeding, because doxylamine passes into breast milk and can cause unusual excitement, irritability, or sedation in a nursing infant.
• Extra caution is needed for infants with breathing pauses (apnea) or other respiratory conditions if exposed through breast milk.

• Doxylamine / Pyridoxine is intended for use in pregnant women; no specific geriatric dosing information applies to this population.

• Doxylamine / Pyridoxine is not intended for use in children, as it is specifically formulated for nausea and vomiting during pregnancy in adult women.

• The usual starting dose is two tablets at bedtime to control morning nausea, plus one tablet in the morning and one tablet in the mid-afternoon if symptoms continue through the day.
• The dosing schedule can be adjusted based on the timing, severity, and pattern of a patient's individual symptoms, under a doctor's guidance.
• This medicine is a delayed-release formulation that works best when taken 4 to 6 hours before symptoms are expected, such as at bedtime for morning sickness, and should be taken on a regular schedule rather than only when symptoms occur.
• Tablets should be swallowed whole and never crushed or split, since this would interfere with the delayed-release action.
• When stopping this medicine, the dose should be gradually reduced (tapered) rather than stopped abruptly, to prevent a sudden return of symptoms.
• If a dose is missed, it should be taken as soon as possible; if it is almost time for the next dose, the missed dose should be skipped rather than doubled.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Because this is a delayed-release medicine, signs of overdose may not appear right away.
• Overdose can cause restlessness, dry mouth, dilated pupils, sleepiness, dizziness, confusion, and a fast heartbeat.
• At higher doses, doxylamine can cause anticholinergic effects including seizures, muscle breakdown (rhabdomyolysis), and, in severe cases, death; cardiorespiratory arrest is a particular risk in children.
• Overdose is managed with gastric lavage or activated charcoal if appropriate, whole bowel irrigation, and supportive symptomatic care; there is no specific antidote.

• Sleepiness (somnolence) may occur, and is the most common side effect.
• Dizziness may occur.
• Tiredness or lack of energy may occur.
• Stomach irritation, heartburn, or indigestion may occur.
• Headache may occur.
• Nervousness may occur.
• Constipation may occur.
• A dry, furry feeling in the mouth may occur.
• Insomnia or vivid dreams may occur in some patients despite the drowsy effect of this medicine.
• Mood changes, such as increased anxiety or irritability, may occur.
• Blurred vision may occur.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Severe drowsiness that interferes with daily activities, including driving, can occur.
• Convulsions (seizures) have been reported rarely, particularly with doses well above the recommended amount.
• Allergic reactions, including swelling of the face or throat (angioedema) and severe skin reactions such as erythema multiforme, can occur rarely.
• Urinary retention (difficulty passing urine) can occur, related to the antihistamine's anticholinergic effects.
• A fast or irregular heartbeat (palpitations or tachycardia) can occur rarely.
• Confusion or disorientation can occur, particularly at higher doses.
• Newborns exposed to this medicine close to delivery have rarely shown withdrawal-type symptoms after birth.
• Rare eye effects, including dilated pupils and sensitivity to light, have been reported.
• Low blood potassium or elevated blood sugar have been reported rarely.
• Seek urgent medical attention for severe drowsiness that cannot be roused, seizures, a fast or irregular heartbeat, or signs of a severe allergic reaction.

• Use with caution in patients with asthma or at risk of an asthma attack, since the antihistamine component can thicken airway secretions.
• Use with caution in patients with narrow-angle glaucoma, given the antihistamine's anticholinergic effects on eye pressure.
• Use with caution in patients with a history of stomach ulcers or any blockage of the stomach outlet or bladder neck, since anticholinergic effects can worsen these conditions.
• Use with caution when combined with alcohol or other medications, due to increased anticholinergic and sedative effects.
• Use with caution in patients who need to drive or operate machinery, since this medicine can cause drowsiness.

• Contraindicated in patients with known hypersensitivity to doxylamine succinate, other ethanolamine-type antihistamines, pyridoxine hydrochloride, or any other ingredient in the product.
• Contraindicated in patients at risk of an asthma attack.
• Contraindicated in patients with narrow-angle glaucoma.
• Contraindicated in patients with a stomach ulcer that narrows the outlet (stenosing peptic ulcer) or any blockage of the stomach outlet.
• Contraindicated in patients with a bladder-neck obstruction.
• Contraindicated in patients taking monoamine oxidase inhibitors (MAOIs), including the antibiotic linezolid and the dye methylene blue.

• Combining with monoamine oxidase inhibitors (MAOIs) can prolong and intensify the effects of the doxylamine component, and is contraindicated.
• Combining with other anticholinergic medications increases the risk of side effects such as dry mouth, blurred vision, constipation, and urinary retention.
• Combining with alcohol or other sedating medications, such as sleep aids, sedatives, tranquilizers, or opioid pain relievers, can increase drowsiness and central nervous system depression.
• The pyridoxine (vitamin B6) component can reduce the effectiveness of levodopa, used for Parkinson's disease, by increasing its breakdown outside the brain.

• Doxylamine / Pyridoxine can be taken with or without food; taking it with food may delay how quickly it starts working, so it is generally taken without regard to meals but with attention to the recommended bedtime and daytime schedule.

• Take the larger, bedtime dose at night to control morning nausea, and take the smaller morning and mid-afternoon doses, if prescribed, at those times to control symptoms throughout the day; this medicine works best taken on a fixed schedule rather than only when symptoms start.

• Store Doxylamine / Pyridoxine tablets at room temperature (15°C to 30°C), protected from light, out of the reach and sight of children.

• Doxylamine / Pyridoxine is taken on a regular schedule, not just when nausea occurs, since it works best when taken ahead of expected symptoms.
• Swallow tablets whole; do not crush or split them.
• Avoid driving or operating machinery until you know how this medicine affects you, since it can cause drowsiness.
• If you wish to stop this medicine, taper the dose gradually with guidance from your doctor or pharmacist rather than stopping suddenly.