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5 Interactions found for:

hydrochlorothiazide and Vitamin B12
Interactions Summary
  • 2 Major
  • 1 Moderate
  • 2 Minor
  • hydrochlorothiazide
  • Vitamin B12

Drug Interactions

No drug interactions were found for selected drugs: hydrochlorothiazide, Vitamin B12.

This does not necessarily mean no interactions exist. Always consult your healthcare provider.

Drug and Food Interactions

Hydrochlorothiazide + Food

The following applies to the ingredients: Hydrochlorothiazide

HydroCHLOROthiazide and ethanol may have additive effects in lowering your blood pressure. You may experience headache, dizziness, lightheadedness, fainting, and/or changes in pulse or heart rate. These side effects are most likely to be seen at the beginning of treatment, following a dose increase, or when treatment is restarted after an interruption. Let your doctor know if you develop these symptoms and they do not go away after a few days or they become troublesome. Avoid driving or operating hazardous machinery until you know how the medications affect you, and use caution when getting up from a sitting or lying position. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Drug and Pregnancy Interactions

The following applies to the ingredients: Hydrochlorothiazide

Professional Content

The manufacturer recommends that hydrochlorothiazide should be used during pregnancy only if the potential benefit outweighs the potential risk to the fetus.

AU TGA pregnancy category: C
US FDA pregnancy category: B

The routine use of diuretics during pregnancy is not indicated or recommended.

Animal studies have failed to reveal evidence of fetal harm. There are no data from controlled human studies, but retrospective reviews have shown an increased risk of malformations associated with thiazide diuretics. In addition, use of thiazide diuretics during pregnancy has been associated with fetal or neonatal electrolyte abnormalities, jaundice, and/or thrombocytopenia.

The Collaborative Perinatal Project monitored 50,282 mother-child pairs, of whom 233 were exposed to thiazide or related diuretics during the first trimester. An increased risk of malformations was found for thiazide diuretics. Use of thiazides after the first trimester does not seem to carry this risk. Thiazide diuretics may, however pose metabolic risks to the mother and fetus (hyponatremia, hypokalemia, thrombocytopenia, hyperglycemia), and may have a direct effect on smooth muscle, resulting in inhibition of labour.

Data from the U.S. Michigan Medicaid Birth Defects Study has revealed an association between the use of hydrochlorothiazide and congenital abnormalities. This was a retrospective study of 229,101 completed pregnancies between 1985 and 1992, of which 567 were exposed to hydrochlorothiazide at some time during the first trimester, and 1,173 were exposed to the drug at any time during pregnancy. Of the 567 pregnancies, there were 24 total and 7 cardiovascular birth defects (22 and 6 were expected, respectively). There were no observations of cleft palate, spina bifida, limb reduction, or hypospadias. The one instance of polydactyly did not achieve statistical significance. These data are consistent with an association between the use of hydrochlorothiazide and birth defects, although other factors, including underlying disease(s) of the mother are not accounted for.

Cases of neonatal thrombocytopenia associated with antepartum administration of thiazide diuretics have been reported.

AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.


  1. Heinonen O, Shapiro S; Kaufman DW ed., Slone D "Birth Defects and Drugs in Pregnancy." Littleton, MA: Publishing Sciences Group, Inc. (1977): 297
  2. Rodriguez SU, Sanford LL, Hiller MC "Neonatal thrombocytopenia associated with ante-partum administration of thiazide drugs." N Engl J Med 270 (1964): 881-4
  3. Lindheimer MD, Katz AI "Sodiuim and diuretics in pregnancy." N Engl J Med 288 (1973): 891-4
  4. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  5. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online." (2006):
  6. Cerner Multum, Inc. "Australian Product Information." O 0

The following applies to the ingredients: Cyanocobalamin (found in Vitamin B12)

Professional Content

This drug should not be used during pregnancy unless the benefit outweighs the risk to the fetus. (AU)

AU TGA pregnancy category: Exempt
US FDA pregnancy category: C

-Vitamin B12 needs are increased in pregnancy.
-Megaloblastic anemia of pregnancy is usually due to folic acid deficiency.
-Do not use for megaloblastic anemia of pregnancy due to folic acid deficiency.


  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. Allen LH "Multiple micronutrients in pregnancy and lactation: an overview." Am J Clin Nutr 81(S) (2005): 1206S-12S
  4. "Product Information. Cyanocobalamin (cyanocobalamin)." West Ward Pharmaceutical Corporation (2017):

Drug and Breastfeeding Interactions

The following applies to the ingredients: Hydrochlorothiazide

Professional Content

Manufacturer recommendation: Use is not recommended and a decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

Excreted into human milk: Yes

According to LactMed this drug has been used without apparent harmful effects in the nursing infant at doses of 50 mg daily or less. Large doses may cause intense diuresis resulting in a decrease in breastmilk production.


  1. "Product Information. HydroDIURIL (hydrochlorothiazide)." Merck & Co., Inc PROD (2002):
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. United States National Library of Medicine "Toxnet. Toxicology Data Network." (2013):

The following applies to the ingredients: Cyanocobalamin (found in Vitamin B12)

Professional Content

Use is not recommended; benefit to mother should outweigh risk to the infant. (AU)

Excreted into human milk: Yes

-Vitamin B12 needs are increased in lactation.
-Deficiency has been seen in breast fed children of vegetarian mothers, even with no symptoms of maternal deficiency.
-Four micrograms daily of B12 are recommended during lactation.


  1. Ehrlich A, Koch T, Amin B, et al. "Development and reliability testing of a standardized questionnaire to assess psoriasis phenotype." J Am Acad Dermatol 54 (2006): 987.e1-14
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. "Product Information. Nascobal (cyanocobalamin)." Par Pharmaceutical Inc (2017):

Therapeutic Duplication Warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

Switch to: Professional Interactions

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.

Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

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