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Doxylamine

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Doxylamine, Unisom, Diclectin, Diclegis, Bendectin

  • See Also
  1. Sedating Antihistamine
  2. Hyperemesis Gravidarum
  3. Antiemetic
  • Indications
  1. Nausea and Vomiting
  2. Hyperemesis Gravidarum
  3. Insomnia
  • Contraindications
  1. Avoid in age <12 years old
  2. Concurrent MAO Inhibitor use
  3. Caution in Narrow Angle Glaucoma
  4. Caution in Benign Prostatic Hyperplasia with obstruction
  • Precautions
  1. Brand-Name Unisom may use Diphenhydramine (Benadryl) instead of Doxylamine for some preparations
  • Mechanism
  1. First-generation histamine Antagonist (Sedating Antihistamine, Ethanolamine)
    1. Competitively blocks H1 Receptors at gastrointestinal Smooth Muscle by maintaining the H1 Receptor in the inactive state
  2. Antiinflammatory properties
    1. Downregulates precursors involved in Antigen Presentation, chemotaxis, cell adhesion and Cytokine production
  • Dosing
  • Doxylamine (Unisom)
  1. Pregnancy Associated Nausea or Vomiting (Morning Sickness, Hyperemesis Gravidarum)
    1. Dose: 10 to 12.5 mg orally up to four times daily
    2. Consider using in combination with Pyrodoxine 10 mg
  2. Insomnia
    1. Dose: 25 mg orally once daily
  • Dosing
  • Combination Doxylamine 10 mg and Pyrodoxine 10 mg (Diclegis, previously Bendectin and Diclectin in Canada)
  1. Dose
    1. Start with 2 tabs orally at bedtime
    2. May advance to 1 tab in AM, 1 tab at Noon and 2 tabs at bedtime as needed
  2. Precautions
    1. Originally pulled from market due to safety concerns that were unsubstantiated
    2. Diclegis is very expensive ($570/month) until generic in 2019
      1. However, generic Doxylamine and Pyridoxine are inexpensive at $20/month
    3. Bonjesta (extended release Doxylamine 20 mg and Pyridoxine 20 mg)
      1. Released in 2018, very expensive and no significant added benefit aside from frequency
  3. References
    1. (2013) Presc Lett 20(6): 32-3
    2. (2018) Presc Lett 25(5): 29
  • Adverse Effects
  1. Anticholinergic
  2. False Positive Urine Drug Screen
    1. May result in a False Positive test for Methadone or other Opiates, or for Phencyclidine (PCP)
  • Resources
  1. Doxylamine (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=96a7c284-4666-4dac-b71e-9433f62580ad
  2. Doxylamine and Pyrodoxine delayed release (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3670d66e-c1e4-42ce-8760-c3d5accad925
  • References
  1. Hamilton (2020) Tarascon Pocket Pharmacopoeia