vitamin B6 analogues
Treatment of nausea and vomiting during pregnancy that has not responded to conservative management.
Combination of an antihistamine and a vitamin B6 analog. Mechanism not known.
Decreased nausea and vomiting associated with pregnancy.
Absorption: Well absorbed following oral administration. Food delays/decreases absorption.
Distribution: Doxylamine probably enters breast milk
Metabolism and Excretion: Doxylamine is mostly metabolized by the liver, inactive metabolites are renally excreted. Pyridoxine is a pro-drug, converted to its active metabolite by the liver.
Half-life: Doxylamine– 12.5 hr; pyridoxine– 0.4–0.5 hr
TIME/ACTION PROFILE (anti-emetic effect)
- Hypersensitivity to doxylamine or pyridoxine
- Concurrent use of MAOIs
- Lactation: Doxylamine probably enters breast milk and may cause irritability, excitement, or sedation in infants; breast feeding should be avoided.
Use Cautiously in:
- ↑ intraocular pressure or narrow angle glaucoma
- Stenosing peptic ulcer or pyloroduodenal obstruction
- Urinary bladder-neck obstruction
- Pedi: Safety and effectiveness not established
Adverse Reactions/Side Effects
* CAPITALS indicate life-threatening.
Underline indicate most frequent.
- ↑ risk of CNS depression with other CNS depressants including alcohol, other antihistamines, opioid analgesics, and sedative/hypnotics.
- Concurrent use of MAOIs ↑ intensity/duration of adverse CNS (anticholinergic) reactions
PO: (Adults) Day 1– 2 tablets (doxylamine 10 mg/pyridoxine 10 mg) at bedtime, if symptoms are controlled continue this regimen; Day 2, if symptoms persist into afternoon on day 2– 2 tablets at bedtime on day 2 and then 1 tablet in the morning on day 3 and 2 tablets in the evening, if symptoms are controlled, continue this regimen; Day 4, if symptoms persist– 1 tablet in the morning, 1 tablet mid-afternoon and 2 tablets at bedtime (not to exceed four tablets daily).
Availability (generic available)
Delayed-release tablets: doxylamine 10 mg/pyridoxine 10 mg
- Assess for frequency and amount of emesis daily during therapy. Reassess need for medication as pregnancy progresses.
- Monitor hydration status to prevent dehydration.
- PO: Administer on an empty stomach with a full glass of water; food delays onset of medication. Swallow tablets whole; do not crush, break, or chew.
- Instruct patient to take as directed.
- May cause drowsiness. Caution patient to avoid driving and other activities requiring alertness until response to medication is known.
- Advise patient to avoid alcohol and CNS depressants, including sedatives, tranquilizers, antihistamines, opioids, and some cough and cold medications with doxylamine pyridoxine.
- Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
- Advise female patient to avoid breast feeding during therapy.
Decrease in frequency of nausea and vomiting during pregnancy.
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