Doxylamine

Aka: Doxylamine, Unisom, Diclectin, Diclegis, Bendectin

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II. Indications

  1. Nausea and Vomiting
  2. Hyperemesis Gravidarum
  3. Insomnia

III. 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

IV. Precautions

  1. Brand-Name Unisom may use Diphenhydramine (Benadryl) instead of Doxylamine for some preparations

V. 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

VI. 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

VII. 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

VIII. 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)

IX. 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

X. References

  1. Hamilton (2020) Tarascon Pocket Pharmacopoeia

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Related Studies

Cost: Medications

doxylamine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
DOXYLAMINE-PYRIDOXINE 10-10 MG Generic $2.54 each
diclegis (on 3/23/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
DICLEGIS DR 10-10 MG TABLET Generic $2.54 each
FPNotebook does not benefit financially from showing this medication data or their pharmacy links. This information is provided only to help medical providers and their patients see relative costs. Insurance plans negotiate lower medication prices with suppliers. Prices shown here are out of pocket, non-negotiated rates. See Needy Meds for financial assistance information. GoodRx is another tool for finding lower drug prices.

Related Topics in Pharmacology

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