Pharmacokinetics of Oral Calcium Carbonate in Parturients

August 10, 2026 updated by: Jessica Ansari, MD, MS, Stanford University
This study investigates the time course of change in calcium in the blood after a pregnant subject takes an oral dose of calcium carbonate (commonly marketed as "Tums"). Midway through the trial, with IRB permission, the oral calcium formulation was switched to calcium citrate to test whether this, better-absorbed formulation might prove more effective in increasing serum calcium. This information is important for trials investigating whether oral calcium can reduce postpartum hemorrhage, bleeding after delivery.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

20

Phase

  • Early Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • California
      • Stanford, California, United States, 94305
        • Stanford Children's Health, Lucile Packard Children's Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Pregnant female subjects at the study institution, admitted for labor (spontaneous, augmented, or induced)

Exclusion Criteria:

  1. severe range blood pressure (BP >160/>110) within the 48 hours prior to delivery
  2. patient age <18 years or >45 years
  3. renal dysfunction with a documented serum Cr > 1.0 mg/dL
  4. known history of congenital or acquired cardiac disease or history of arrhythmia
  5. patient taking digoxin
  6. patient currently taking a calcium channel blocker
  7. Weight <55kg or >100kg, or
  8. receiving magnesium infusion within 24 hours prior to or during cesarean delivery
  9. Prior or planned administration of calcium by the obstetric or anesthesiology teams for clinical indications within 24 hours of study enrollment
  10. Patient took a calcium supplement in the past 48 hours
  11. Patient status is NPO (nothing by mouth) as ordered by the clinical team

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Non-Randomized
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Oral calcium carbonate
Patients take a single dose of oral calcium carbonate 1200mg
Drug: Oral calcium carbonate
Participants receive a single, open-label dose of oral calcium carbonate 1200mg
Experimental: Oral calcium citrate
Participants receive a single oral dose of calcium citrate 1250mg
Drug: Oral calcium citrate
Participants receive a single oral dose of calcium citrate 1250mg

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Ionized calcium concentration
Time Frame: 4 hours
Ionized calcium (mmol/L) is measured at baseline and over 5 additional convenience timepoints over the 4 hours after ingestion of calcium carbonate 3000mg.
4 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Stanford University

Investigators

  • Principal Investigator: Jessica Ansari, MD, MS, Stanford University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 23, 2025

Primary Completion (Actual)

October 11, 2025

Study Completion (Actual)

December 3, 2025

Study Registration Dates

First Submitted

October 18, 2024

First Submitted That Met QC Criteria

October 18, 2024

First Posted (Actual)

October 21, 2024

Study Record Updates

Last Update Posted (Actual)

August 12, 2026

Last Update Submitted That Met QC Criteria

August 10, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 77182

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Patient privacy

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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