Calcium is a life saving medicine in the care of parturients. It has many important uses including treatment of hypocalcemia, treatment of magnesium toxicity, prevention of hypocalcemia during blood transfusion (of citrate containing blood products), treatment of hyperkalemia, and others. Recent clinical trials also suggest that calcium given after cord clamping may decrease blood loss in patients undergoing cesarean delivery. 2 FDA approved forms of calcium can be given intravenously: calcium chloride and calcium gluconate. Over the last decade there have been times with drug shortages of either calcium chloride or calcium gluconate. So there have been and likely will continue to be times when one formulation or the other may not be adequately available. Despite the importance of calcium and the frequency in which it is used in parturients, there are no published studies in parturients to determine dose equivalence between calcium gluconate and calcium chloride. In this study the investigators will determine the population pharmacokinetics of calcium gluconate and calcium chloride in parturients and calculate the dose equivalent ratio the two drugs. This will help clinicians select appropriate doses of calcium and provide resilience to the drug supply chain in our era of frequent drug shortages.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
34
Infused intravenously over 10 minutes upon umbilical cord clamping. First 10 assigned patients received 2 grams per protocol. Subsequent 13 patients received 1.5 grams, dose recalibrated per protocol.
0.5 grams of calcium chloride, infused intravenously over 10 minutes upon umbilical cord clamping
Lucile Packard Children's Hospital
Stanford, California, United States
Bioequivalent ratio of calcium gluconate (g) to calcium chloride (g)
Calculated via NONMEM
Time frame: Using data gathered from serial lab draws at 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Clearance from first to second compartment (L/min)
Determined using population pharmacokinetic analysis in NONMEM
Time frame: Using data gathered from serial lab draws at 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Volume of distribution of first compartment of pharmacokinetic model (L)
Determined using population pharmacokinetic analysis in NONMEM
Time frame: Using data gathered from serial lab draws at 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Clearance from second compartment (L/min)
Determined using population pharmacokinetic analysis in NONMEM
Time frame: Using data gathered from serial lab draws at 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Volume of distribution of second compartment of pharmacokinetic model (L)
Determined using population pharmacokinetic analysis in NONMEM
Time frame: Using data gathered from serial lab draws at 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Serum pH
Serum pH will be measured in each participant from a maximum of 6 venous blood draws of 0.5mL (1/10th of a teaspoon). These blood draws will be the same blood draws used to measure serum ionized calcium concentration, no additional blood draws will be necessary. These draws will occur at the following target times: prior to calcium administration, at 6 minutes, 10 minutes, 15 minutes, minutes, minutes after beginning calcium administration. The serum pH levels will be immediately analyzed using an Abbott iStat machine.
Time frame: Baseline prior to calcium infusion, 6 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes after initiation of infusion
Baseline serum ionized calcium concentration
Ionized calcium will be measured in each participant prior to administration of the 10-minute calcium infusion. The ionized blood calcium levels will be immediately analyzed using an Abbott iStat machine.
Time frame: Baseline prior to calcium infusion
Peak change in serum ionized calcium concentration (mmol/L)
Measured via venous blood draw and an Abbott iStat CG8+ cartridge
Time frame: Measured immediately at completion of the 10-minute calcium infusion.
Time to half of peak change in ionized calcium (minutes)
A two-compartment model does not lend itself to a meaningful half-life approximation. However, the time to serum values measuring 1/2 of the peak change in ionized calcium can be calculated from the pharmacokinetic model
Time frame: 10-60 minutes after infusion initiation
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