doxylamine succinate + pyridoxine hydrochloride: clinical use

Prescribing considerations

• Licensed for pregnant adults who have not responded to conservative management.
• Hyperemesis gravidarum requires specialist treatment because evidence for this combination is limited.
• Assess concurrent CNS depressants, alcohol use and total vitamin B6 exposure.
• Drowsiness can substantially impair driving and operation of machinery.
• Pharmacokinetic studies have not been conducted in renal or hepatic impairment.

Contraindications and cautions

• Hypersensitivity to doxylamine, pyridoxine, other ethanolamine-derived antihistamines or an excipient.
• Concomitant monoamine oxidase inhibitor use.
• Use caution with asthma, raised intraocular pressure, narrow-angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction or bladder-neck obstruction.

Monitoring

• Review symptom response and continued clinical need as pregnancy progresses.
• Monitor sedation and anticholinergic effects, including visual disturbance and urinary retention.
• Consider confirmatory testing after positive urine immunoassays for methadone, opiates or PCP because false positives can occur.

Clinical pharmacology

Doxylamine is a brain-penetrant, first-generation H1 antihistamine with anticholinergic and antiemetic effects. Pyridoxine is converted to biologically active metabolites, principally pyridoxal phosphate; renal excretion is important for metabolites of both components.

Formulation and product differences

• The selected product is a gastro-resistant, delayed-release tablet that must remain intact.
• Taking it with food delays absorption and can reduce pyridoxine bioavailability.
• The formulation contains Allura red AC, which may cause allergic reactions, and is essentially sodium-free.

Gastro-resistant tablet

Route: Oral

Strengths: 10 mg + 10 mg