How does Diclectin (doxylamine and pyridoxine) prevent nausea?

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Last updated: June 11, 2025View editorial policy

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From the Guidelines

Diclectin prevents nausea through the combined action of its two active ingredients: doxylamine succinate and pyridoxine hydrochloride (vitamin B6), which work synergistically to block histamine H1 receptors and modulate neurotransmitters involved in nausea signaling pathways. The mechanism of action of Diclectin involves doxylamine, an antihistamine that blocks histamine H1 receptors in the brain, reducing the stimulation of the vomiting center in the medulla oblongata 1. This antihistamine component also has sedative properties that can help with sleep disturbances often associated with nausea, particularly in pregnancy. Pyridoxine (vitamin B6) works through a different mechanism, helping to regulate certain neurotransmitters involved in nausea signaling pathways, and appears to modulate serotonin levels, which play a role in triggering nausea and vomiting 1. The standard dosing for Diclectin is typically 2 tablets at bedtime, with additional tablets in the morning and afternoon as needed, based on symptom severity. Key benefits of using Diclectin for nausea prevention include:

  • Addressing multiple pathways involved in nausea generation
  • Maintaining a favorable safety profile for use during pregnancy
  • Reducing the risk of progression to hyperemesis gravidarum with early treatment 1. Overall, Diclectin is a safe and effective option for managing nausea and vomiting during pregnancy, and its use is supported by recent clinical practice updates 1.

From the Research

Mechanism of Action

  • Diclectin, a combination of doxylamine and pyridoxine, is used to prevent nausea and vomiting of pregnancy (NVP) 2, 3.
  • The exact mechanism of how Diclectin prevents nausea is not fully understood, but it is believed that doxylamine, an antihistamine, helps to reduce the symptoms of NVP by blocking the histamine receptors in the brain, while pyridoxine, a form of vitamin B6, helps to alleviate nausea and vomiting 4, 5.

Efficacy of Diclectin

  • Studies have shown that Diclectin is effective in reducing the symptoms of NVP, with a significant improvement in nausea and vomiting scores compared to placebo 3, 4.
  • A randomized, double-blind, multicenter placebo-controlled trial found that Diclectin resulted in a significantly larger improvement in symptoms of NVP compared to placebo, with 64% of women receiving Diclectin asking to continue compassionate use of their medication after the trial 3.
  • Another study found that bi-daily combination therapy with pyridoxine and doxylamine was efficacious in treating NVP, with 69% of women experiencing relief from symptoms 4.

Safety Considerations

  • Diclectin has been shown to be safe for use during pregnancy, with no increased fetal risk for congenital malformations and other adverse pregnancy outcomes 2, 6.
  • Studies have found that the combination of doxylamine and pyridoxine has a favorable safety profile, with no significant increase in fetal risks or congenital anomalies 2, 6.
  • However, it is essential to follow the recommended dosage and to consult with a healthcare provider before taking Diclectin, as suboptimal dosing may not provide adequate relief from symptoms 5.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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