Pharmacokinetics of intravenous ketorolac following caesarean delivery

Prediction of Pregnancy-Induced Changes in Secretory and Total Renal Clearance of Drugs Transported by Organic Anion Transporters

Pregnancy can significantly change the pharmacokinetics of drugs, including those renally secreted by organic anion transporters (OATs). Quantifying these changes in pregnant women is logistically and ethically challenging. Hence, predicting the in vivo plasma renal secretory clearance (CLsec) and renal CL (CLrenal) of OAT drugs in pregnancy is important to design correct dosing regimens of OAT drugs. Here, we first quantified the fold-change in renal OAT activity in pregnant versus nonpregnant individual using available selective OAT probe drug CLrenal data (training dataset; OAT1: tenofovir, OAT2: acyclovir, OAT3: oseltamivir carboxylate). The fold-change in OAT1 activity during the 2nd and 3rd trimester was 2.9 and 1.0 compared with nonpregnant individual, respectively. OAT2 activity increased 3.1-fold during the 3rd trimester. OAT3 activity increased 2.2, 1.7 and 1.3-fold during the 1st, 2nd, and 3rd trimester, respectively. Based on these data, we predicted the CLsec, CLrenal and total clearance ((CLtotal) of drugs in pregnancy, which are secreted by multiple OATs (verification dataset; amoxicillin, pravastatin, cefazolin and ketorolac, R-ketorolac, S-ketorolac). Then, the predicted clearances (CLs) were compared with the observed values. The predicted/observed CLsec, CLrenal, and CLtotal of drugs in pregnancy of all verification drugs were within 0.80-1.25 fold except for CLsec of amoxicillin in the 3rd trimester (0.76-fold) and cefazolin in the 2nd trimester (1.27-fold). Overall, we successfully predicted the CLsec, CLrenal, and CLtotal of drugs in pregnancy that are renally secreted by multiple OATs. This approach could be used in the future to adjust dosing regimens of renally secreted OAT drugs which are administered to pregnant women. SIGNIFICANCE STATEMENT: To the authors' knowledge, this is the first report to successfully predict renal secretory clearance and renal clearance of multiple OAT substrate drugs during pregnancy. The data presented here could be used in the future to adjust dosing regimens of renally secreted OAT drugs in pregnancy. In addition, the mechanistic approach used here could be extended to drugs transported by other renal transporters.

Clinical Pharmacokinetic Studies in Pregnant Women and the Relevance of Pharmacometric Tools

BACKGROUND

In clinical pharmacokinetic (PK) studies, pregnant women are significantly underrepresented because of ethical and legal reasons which lead to a paucity of information on potential PK changes in this population. As a consequence, pharmacometric tools became instrumental to explore and quantify the impact of PK changes during pregnancy.

METHODS

We explore and discuss the typical characteristics of population PK and physiologically based pharmacokinetic (PBPK) models with a specific focus on pregnancy and postpartum.

RESULTS

Population PK models enable the analysis of dense, sparse or unbalanced data to explore covariates in order to (partly) explain inter-individual variability (including pregnancy) and to individualize dosing. For population PK models, we subsequently used an illustrative approach with ketorolac data to highlight the relevance of enantiomer specific modeling for racemic drugs during pregnancy, while data on antibiotic prophylaxis (cefazolin) during surgery illustrate the specific characteristics of the fetal compartments in the presence of timeconcentration profiles. For PBPK models, an overview on the current status of reports and papers during pregnancy is followed by a PBPK cefuroxime model to illustrate the added benefit of PBPK in evaluating dosing regimens in pregnant women.

CONCLUSIONS

Pharmacometric tools became very instrumental to improve perinatal pharmacology. However, to reach their full potential, multidisciplinary collaboration and structured efforts are needed to generate more information from already available datasets, to share data and models, and to stimulate cross talk between clinicians and pharmacometricians to generate specific observations (pathophysiology during pregnancy, breastfeeding) needed to further develop the field.

Comparison of the Post-Caesarean Analgesic Effect of Adding Dexmedetomidine to Paracetamol and Ketorolac: A Randomized Clinical Trial

Background

Paracetamol and non-steroidal anti-inflammatory drugs (e.g. ketorolac) can be considered for mild to moderate post-caesarean pain. As a selective α-2 agonist adrenergic receptor, dexmedetomidine has analgesic and sedative effects without causing respiratory depression.

Objectives

This study aimed to evaluate the effects of adding dexmedetomidine to paracetamol or ketorolac on post-caesarean pain and the associated complications thereof.

Methods

Sixty pregnant women, who were candidates for caesarean section with spinal anesthesia, were randomly assigned to either of two groups of 30 patients. For post-operative pain management, an intravenous patient-controlled analgesia (PCA) device was used for 24 hours. Dexmedetomidine (3 µg kg^-1) was added to paracetamol (35 mg kg^-1) in the group DP and to ketorolac (1 mg kg^-1) in the group DK. Visual analog scale (VAS), Ramsay sedation scale, hemodynamic changes, rescue analgesic (meperidine) consumption, patient satisfaction, and possible complications were recorded at 6, 12, and 24, hours after surgery, and compared afterward.

Results

The pain score was significantly lower in the DK group than in the DP group (P < 0.05). The hemodynamics and sedation scale were similar in both groups. The total meperidine consumption was higher in the DP group, but it was not significantly different. Maternal satisfaction was greater in the DK group (P < 0.05). Concerning complications, the two groups did not show statistically significant differences (P = 0.4).

Conclusions

The addition of dexmedetomidine to ketorolac, compared with its addition to paracetamol, causes further reduction in the post-operative pain score and provides more satisfaction.

Perinatal and neonatal use of paracetamol for pain relief

Paracetamol (acetaminophen) is the most widely used drug to treat pain or fever in pregnant women or neonates, but its pharmacokinetics (PK) and pharmacodynamics (PD) warrant a focused analysis. During pregnancy, there is an important increase in paracetamol clearance. Consequently, it is reasonable to anticipate that the analgesic effect of paracetamol will decrease faster, whereas higher doses may result in even higher oxidative toxic metabolites. Therefore, most peripartal PD data relate to multimodal analgesia strategies. In neonates, weight/size is the most relevant covariate of paracetamol PK. This resulted in proposed dosing regimens containing higher doses than currently prescribed in the label for term neonates. Using adequate dosing, paracetamol is a poor procedural analgesic, is effective for mild-to-moderate pain, and has morphine-sparing effects. Short-term safety has been well documented, and there is active research investigating the potential association between paracetamol exposure and atopy, fertility, and neurobehavior.

Body weight, gender and pregnancy affect enantiomer-specific ketorolac pharmacokinetics

AIMS

Although ketorolac analgesia is linked only to the S-enantiomer, there is limited information on the stereo-selective pharmacokinetics of this agent. We studied the stereo-selective pharmacokinetics of ketorolac in a pooled dataset of two studies, with women at delivery and 4-5 months postpartum, and males and nonpregnant females.

METHODS

Nonlinear mixed-effect modelling was used to evaluate the stereo-selective pharmacokinetics of ketorolac tromethamine after a single intravenous injection immediately after delivery (n = 41), 4-5 months postpartum (n = 8, paired), and in male (n = 12) and nonpregnant female (n = 14) subjects. All of the males and six of the nonpregnant females were recruited from another study, in which they were undergoing blood sampling for 24 h. All remaining cases underwent blood sampling for 8 h.

RESULTS

For both the R- and S-enantiomers, body weight affected ketorolac clearance. In addition, clearance for both enantiomers was 36% [95% confidence interval (CI) 15%, 58%] higher in male than in female subjects of the same body weight, and 55% (95% CI 33%, 78%) higher in women at delivery than in nonpregnant women of the same body weight. Women at delivery also had a 27% (95% CI 8%, 46%) higher distribution volume than nonpregnant women. The proportional effects of the covariates were not significantly different for the two ketorolac enantiomers.

CONCLUSIONS

Besides the anticipated impact of body weight on clearance, R- and S-ketorolac clearance is increased in male subjects and in women at delivery. To reach an exposure equivalent to that in nonpregnant women, males should receive a 36% increased ketorolac dose and pregnant women a 55% increased dose, in addition to a dose adjustment by body weight.

Enantiomer-specific ketorolac pharmacokinetics in young women, including pregnancy and postpartum period

Racemic ketorolac clearance (CL) is significantly higher at delivery, but S-ketorolac disposition determines the analgesic effects. The aim of this study was to investigate the effect of pregnancy and postpartum period on enantiomer-specific (S and R) intravenous (IV) ketorolac pharmacokinetics (PKs). Data in women shortly following cesarean delivery (n=39) were pooled with data in a subgroup of these women that was reevaluated in the later postpartum period (postpartum group, n=8/39) and with eight healthy female volunteers. All women received single IV bolus of 30 mg ketorolac tromethamine. Five plasma samples were collected at 1, 2, 4, 6, and 8 hours and plasma concentrations were determined using high performance liquid chromatography. Enantiomer-specific PKs were calculated using PKSolver. Unpaired analysis showed that distribution volume at steady state (Vss, L/kg) for S- and R-ketorolac was significantly higher in women shortly following cesarean delivery (n=31) compared to postpartum group (n=8) or to healthy female volunteers (n=8). CL, CL to body weight, and CL to body surface area (CL/BSA) for S- and R-ketorolac were also significantly higher in women following delivery. In addition, S/R-ketorolac CL/BSA ratio was significantly higher at delivery. Paired PK analysis in eight women shortly following delivery and in postpartum group showed the same pattern. Finally, the simultaneous increase in CL and Vss resulted in similar estimates for elimination half-life in both unpaired and paired analysis. In conclusion, pregnancy affects S-, R-, and S/R-ketorolac disposition. This is of clinical relevance since S-ketorolac (analgesia) CL is even more increased compared to R-ketorolac CL, and S/R-ketorolac CL ratio is higher following delivery compared to postpartum period or to healthy female volunteers.

Dexmedetomidine in Postoperative Analgesia in Patients Undergoing Hysterectomy: A CONSORT-Prospective, Randomized, Controlled Trial

Both dexmedetomidine and sufentanil modulate spinal analgesia by different mechanisms, and yet no human studies are available on their combination for analgesia during the first 72 hours after abdominal hysterectomy.This CONSORT-prospective, randomized, double-blinded, controlled trial sought to evaluate the safety and efficacy of the combination of dexmedetomidine and sufentanil in intravenous patient-controlled analgesia (PCA) for 72 hours after abdominal hysterectomy.Ninety women undergoing total abdominal hysterectomy were divided into 3 equal groups that received sufentanil (Group C; 0.02 μg/kg/h), sufentanil plus dexmedetomidine (Group D1; 0.02 μg/kg/h, each), or sufentanil (0.02 μg/kg/h) plus dexmedetomidine (0.05 μg/kg/h) (Group D2) for 72 hours after surgery in this double-blinded, randomized study. The primary outcome measure was the postoperative sufentanil consumption, whereas the secondary outcome measures were pain intensity (visual analogue scale), requirement of narcotic drugs during the operation, level of sedation, Bruggrmann comfort scale, and concerning adverse effects.The postoperative sufentanil consumption was significantly lower in Groups D1 and D2 than in Group C during the observation period (P < 0.05), but lower in Group D2 than in Group D1 at 24, 48, and 72 hours after surgery (P < 0.05). The heart rate after intubation and incision was lower in Groups D1 and D2 than in Group C (P < 0.05). On arrival at the recovery room, Groups D1 and D2 had lower mean blood pressure than Group C (P < 0.05). The intraoperative requirement of sevoflurane was 30% lesser in Groups D1 and D2 than in Group C. The sedation levels were greater in Groups D1 and D2 during the first hour (P < 0.05). Compared with Groups C and D1, Group D2 showed lower levels of the overall incidence of nausea and vomiting (P < 0.05).Among the tested PCA options, the addition of dexmedetomidine (0.05 μg/kg/h) and sufentanil (0.02 μg/kg/h) showed better analgesic effect and greater patient satisfaction without other clinically relevant side effects for patients undergoing hysterectomy during the first 72 hours after abdominal hysterectomy.