PregnancyEarly Phase 1NCT06650930
Pharmacokinetics of Oral Calcium Carbonate in Parturients
A Early Phase 1 study testing Oral calcium carbonate and Oral calcium citrate in people with Pregnancy and Pharmacokinetics, run by Stanford University at 1 site in United States.
Trial summary
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… Read more about this study
- Who is it for?
- Ages 18 to 45 years, women only
- Conditions the study is for
- Pregnancy, Pharmacokinetics, Postpartum Hemorrhage
- What is being tested?
- Oral calcium carbonate and Oral calcium citrate
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 1 siteUnited States
- Study dates
- 23 Jan 2025to 3 Dec 2025
- Phase
- Early Phase 1
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 45 years
- Women only
- No healthy volunteers
- Adult
Who may be able to join
- Pregnant female subjects at the study institution, admitted for labor (spontaneous, augmented, or induced)
Who cannot join
- severe range blood pressure (BP >160/>110) within the 48 hours prior to delivery
- patient age <18 years or >45 years
- renal dysfunction with a documented serum Cr > 1.0 mg/dL
- known history of congenital or acquired cardiac disease or history of arrhythmia
- patient taking digoxin
- patient currently taking a calcium channel blocker
Show all 11Show fewer
- Weight <55kg or >100kg, or
- receiving magnesium infusion within 24 hours prior to or during cesarean delivery
- Prior or planned administration of calcium by the obstetric or anesthesiology teams for clinical indications within 24 hours of study enrollment
- Patient took a calcium supplement in the past 48 hours
- Patient status is NPO (nothing by mouth) as ordered by the clinical team
Trial locations and contacts
1 site in 1 country.
United States1 site
Stanford Children's Health, Lucile Packard Children's Hospital
Stanford, California, 94305
About this study
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.
- Conditions
- Pregnancy, Pharmacokinetics, Postpartum Hemorrhage
- Being tested
- Oral calcium carbonate, Oral calcium citrate
- Keywords
- calcium, oral calcium, calcium carbonate, calcium pharmacokinetics, pharmacokinetics in pregnancy, postpartum hemorrhage, ionized calcium, pharmacokinetics
- Medical subject headings
- Postpartum Hemorrhage
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Oral calcium carbonateDrug
Participants receive a single, open-label dose of oral calcium carbonate 1200mg
Oral calcium citrateDrug
Participants receive a single oral dose of calcium citrate 1250mg
| Study group | Role | What they receive |
|---|---|---|
| Oral calcium carbonate | Experimental | Patients take a single dose of oral calcium carbonate 1200mg Receives: Drug: Oral calcium carbonate |
| Oral calcium citrate | Experimental | Participants receive a single oral dose of calcium citrate 1250mg Receives: Drug: Oral calcium citrate |
What is being measured
The primary outcome is the main question the study is designed to answer.
Ionized calcium concentration
Ionized calcium (mmol/L) is measured at baseline and over 5 additional convenience timepoints over the 4 hours after ingestion of calcium carbonate 3000mg.
Measured: 4 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted21 Oct 2024
- Study start23 Jan 2025
- Primary completion11 Oct 2025
- Study completion3 Dec 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for PregnancyStudies of the same condition, open and under way.
- More trials run by Stanford UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Early Phase 1
- Primary purpose
- Other
- Allocation
- Non-randomised
- Intervention model
- Single group
- Model description
- This is a single arm pharmacokinetic trial. No efficacy outcomes are analyzed. The aim of the study is to determine the pharmacokinetics of a single dose of oral calcium carbonate or calcium citrate in parturients. The outcome of interest is serial measurement of the ionized calcium in the blood.
- Masking
- None (open label)
- Enrolment
- 20 participants (actual)
Sponsor and investigators
- Lead sponsor
- Stanford University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Jessica Ansari, MD, MS, Stanford University
- Investigators
- Jessica Ansari, MD, MS, Principal investigator, Stanford University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06650930
- Sponsor's protocol ID
- 77182
- Status last verified
- Aug 2026
- First submitted
- 18 Oct 2024
- Last updated
- 12 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: Patient privacy
Publications
Ansari JR, Yarmosh A, Michel G, Lyell D, Hedlin H, Cornfield DN, Carvalho B, Bateman BT. Intravenous Calcium to Decrease Blood Loss During Intrapartum Cesarean Delivery: A Randomized Controlled Trial. Obstet Gynecol. 2024 Jan 1;143(1):104-112. doi: 10.1097/AOG.0000000000005441. Epub 2023 Nov 3.
PubMed 37917943Ansari JR, Kalariya N, Carvalho B, Flood P, Guo N, Riley E. Calcium chloride for the prevention of uterine atony during cesarean delivery: A pilot randomized controlled trial and pharmacokinetic study. J Clin Anesth. 2022 Sep;80:110796. doi: 10.1016/j.jclinane.2022.110796. Epub 2022 Apr 18.
PubMed 35447502Ansari JR, Conti DJ, Michel G, Yarmosh A, Cole NM, Shafer SL. Bioequivalence and Pharmacokinetics of Intravenous Calcium during Cesarean Delivery. Anesthesiology. 2025 Jan 1;142(1):121-131. doi: 10.1097/ALN.0000000000005248.
PubMed 39361822Ansari J, Carvalho B, Shafer SL, Flood P. Pharmacokinetics and Pharmacodynamics of Drugs Commonly Used in Pregnancy and Parturition. Anesth Analg. 2016 Mar;122(3):786-804. doi: 10.1213/ANE.0000000000001143.
PubMed 26891392
Study at a glance
From the registry record, last updated by the sponsor on 12 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pharmacokinetics of Oral Calcium Carbonate in Parturients
- ClinicalTrials.gov ID
- NCT06650930
- Acronym / sponsor ID
- 77182
- Conditions
- Pregnancy, Pharmacokinetics, Postpartum Hemorrhage
- Keywords
- calcium, oral calcium, calcium carbonate, calcium pharmacokinetics, pharmacokinetics in pregnancy, postpartum hemorrhage, ionized calcium, pharmacokinetics
- Phase
- Early Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 20 participants (actual)
- Lead sponsor
- Stanford UniversityUniversity, hospital or other
- Study start
- 23 Jan 2025 (actual)
- Primary completion
- 11 Oct 2025 (actual)
- Study completion
- 3 Dec 2025 (actual)
- First posted
- 21 Oct 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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 design
- Primary purpose
- Other
- Allocation
- Non-randomised
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- This is a single arm pharmacokinetic trial. No efficacy outcomes are analyzed. The aim of the study is to determine the pharmacokinetics of a single dose of oral calcium carbonate or calcium citrate in parturients. The outcome of interest is serial measurement of the ionized calcium in the blood.
| Arm | Type | Receives |
|---|---|---|
| Oral calcium carbonate | Experimental | Drug: Oral calcium carbonatePatients take a single dose of oral calcium carbonate 1200mg |
| Oral calcium citrate | Experimental | Drug: Oral calcium citrateParticipants receive a single oral dose of calcium citrate 1250mg |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (1 listed)
- Pregnant female subjects at the study institution, admitted for labor (spontaneous, augmented, or induced)
Key exclusion criteria (11 listed)
- severe range blood pressure (BP >160/>110) within the 48 hours prior to delivery
- patient age <18 years or >45 years
- renal dysfunction with a documented serum Cr > 1.0 mg/dL
- known history of congenital or acquired cardiac disease or history of arrhythmia
- patient taking digoxin
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Oral calcium carbonateParticipants receive a single, open-label dose of oral calcium carbonate 1200mg | Drug | Oral calcium carbonate |
| Oral calcium citrateParticipants receive a single oral dose of calcium citrate 1250mg | Drug | Oral calcium citrate |
Primary outcome
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.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 12 Aug 2026.
- Background: PubMed 37917943Ansari JR, Yarmosh A, Michel G, Lyell D, Hedlin H, Cornfield DN, Carvalho B, Bateman BT. Intravenous Calcium to Decrease Blood Loss During Intrapartum Cesarean Delivery: A Randomized Controlled Trial. Obstet Gynecol. 2024 Jan 1;143(1):104-112. doi: 10.1097/AOG.0000000000005441. Epub 2023 Nov 3.
- Background: PubMed 35447502Ansari JR, Kalariya N, Carvalho B, Flood P, Guo N, Riley E. Calcium chloride for the prevention of uterine atony during cesarean delivery: A pilot randomized controlled trial and pharmacokinetic study. J Clin Anesth. 2022 Sep;80:110796. doi: 10.1016/j.jclinane.2022.110796. Epub 2022 Apr 18.
- Background: PubMed 39361822Ansari JR, Conti DJ, Michel G, Yarmosh A, Cole NM, Shafer SL. Bioequivalence and Pharmacokinetics of Intravenous Calcium during Cesarean Delivery. Anesthesiology. 2025 Jan 1;142(1):121-131. doi: 10.1097/ALN.0000000000005248.
- Background: PubMed 26891392Ansari J, Carvalho B, Shafer SL, Flood P. Pharmacokinetics and Pharmacodynamics of Drugs Commonly Used in Pregnancy and Parturition. Anesth Analg. 2016 Mar;122(3):786-804. doi: 10.1213/ANE.0000000000001143.
- Individual participant dataSharing planned: No. Patient privacy
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Jessica Ansari, MD, MS principal investigator
Stanford University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Early Phase 1 study testing Oral calcium carbonate and Oral calcium citrate in people with Pregnancy and Pharmacokinetics, run by Stanford University at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 11 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 12 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Ionized calcium concentration (time frame: 4 hours). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06650930, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Aug 2026.