Ketorolac tromethamine: stereo-specific pharmacokinetics and single-dose use in postoperative infants aged 2-6 months

Early Utilization of Ketorolac in Cleft Palate Repair

OBJECTIVE

To determine the effect of ketorolac on opiate requirement and hospital length of stay after palatoplasty.

DESIGN

This was a retrospective chart review.

SETTING

This study was completed at an urban tertiary medical center.

PATIENTS

Those who underwent palatoplasty with a pediatric otolaryngologist between 2010-2020.

INTERVENTIONS

Incorporation of standing Ketorolac into the immediate post-operative pain regimen.

MAIN OUTCOME MEASURES

T-test analysis was performed to determine whether initiation of ketorolac within 24 h post-palatoplasty was correlated with shorter length hospitalization or reduced opiate requirement.

RESULTS

A total of 55 pediatric subjects (49.1% female) were included in this study. Average age at time of surgery was 13 months (range 9.9-33.9 months). On two tailed t-test, use of ketorolac within the first 24 h after palatoplasty was associated with shorter length of stay (mean of 1.68 vs 2.57 days, t = 2.58, P = .01) and lower total opiate dosage during hospitalization (mean of 2.8 vs 9.16 morphine milligram equivalents, t = 3.37, P = .001).

CONCLUSIONS

Among patients undergoing palatoplasty, there is a significant relationship between the early utilization of ketorolac and decreased length of hospitalization as well as decreased opiate requirement. This has important consequences to help improve pain control with reduced opiates requirement as well as length of stay. Future prospective studies can help elicit the causative effect of Ketorolac on these parameters and can investigate whether use of Ketorolac has an effect on long term recovery and post-discharge opiate requirements as well.

Ketorolac Dosing and Outcomes in Neonates Following Congenital Heart Surgery: A Retrospective Analysis

BACKGROUND

Pain management is essential for postoperative surgery. Given the association of opioids with adverse outcomes, interest in the use of nonopioid analgesics, such as ketorolac, has increased. Published data on use in neonates are limited.

OBJECTIVES

To describe ketorolac dosing and safety and efficacy outcomes in the first 48 hours postcardiac surgery in neonates.

DESIGN

We performed a single-center retrospective cohort study of neonates (ages < 28 d) who received ketorolac following cardiac surgery from November 2020 to July 2023 (inclusive). The primary safety outcome was a clinically significant decline in renal function, as defined by the composite of an increase in serum creatinine by greater than or equal to 0.3 mg/dL from baseline within 96 hours of ketorolac initiation and urine output less than or equal to 0.5 mL/kg/hr for 6 hours. The secondary safety outcome was clinically significant bleeding, defined as the composite of major bleeding by the International Society on Thrombosis and Hemostasis pediatric criteria and severe/fatal bleeding by the criteria of Nellis et al (2019). Efficacy was measured by opioid utilization based on a standardized pain score-driven analgesia protocol.

INTERVENTIONS

Ketorolac was administered at 0.5 mg/kg every 6 hours as per an institutional clinical management algorithm.

MEASUREMENTS AND MAIN RESULTS

Thirty-nine patients met the eligibility criteria. The median ketorolac dose was 0.5 mg/kg/dose, and median (interquartile range [IQR]) duration of therapy was 48 hours (6-48 hr). No patients experienced a significant decline in renal function, and there were no clinically significant bleeding events. The median (IQR) IV morphine milligram equivalents (MMEs)/kg/d of opioid administration was 0.2 MME/kg/d (0.1-0.25 MME/kg/d) at the time of ketorolac initiation and 0.1 MME/kg/d (0.1-0.2 MME/kg/d) at 48 hours post-ketorolac initiation.

CONCLUSIONS

If validated prospectively, these findings suggest that a ketorolac regimen of 0.5 mg/kg/dose every 6 hours in neonates postcardiac surgery may be safe with regard to renal function and bleeding risk. Additional randomized studies would be needed to determine efficacy with regard to opioid-sparing capacity.

Ketorolac in neonates and infants following congenital heart surgery: a retrospective review

INTRODUCTION

Pain management is essential in the immediate post-surgical period. We sought to describe the ketorolac dose regimen in neonates and infants following cardiac surgery. Secondary outcomes included renal dysfunction, bleeding, and pain management.

METHODS

We performed a single-centre retrospective cohort study of neonates and infants (aged < 12 months) who received ketorolac following cardiac surgery, from November 2020 through November 2021 (inclusive). Ketorolac was administered at 0.5 mg/kg every 6 hours. Safety was defined by absence of a clinically significant decline in renal function (i.e., increase in serum creatinine [SCr] by ≥ 0.3 mg/dL from baseline within 48 hours and/or urine output ≤ 0.5 mL/kg/hour for 6 hours) and absence of clinically significant bleeding defined as major by International Society on Thrombosis and Hemostasis paediatric criteria or Severe/Fatal Bleeding Events by Nellis et al. Efficacy measures included pain scores and opioid utilisation.

RESULTS

Fifty-five patients met eligibility criteria. The median (range) dose and duration of ketorolac administration was 0.5 mg/kg/dose for 48 (6-90) hours. Among all patients, there was not a statistically significant difference observed in median SCr within 48 hours of baseline (p > .9). There were no major or severe bleeding events. The median (range) opioid requirements (morphine intravenous equivalents per kg per day) at 48 hours post-ketorolac initiation was 0.1 (0-0.8) mg/kg/day.

CONCLUSIONS

If validated prospectively, these findings suggest that a ketorolac regimen 0.5 mg/kg/dose every 6 hours in neonates and infants post-cardiac surgery may be safe with regard to renal function and bleeding risk, and effective regarding opioid-sparing capacity.

Efficacy and Safety of NSAIDs in Infants: A Comprehensive Review of the Literature of the Past 20 Years

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used in infants, children, and adolescents worldwide; however, despite sufficient evidence of the beneficial effects of NSAIDs in children and adolescents, there is a lack of comprehensive data in infants. The present review summarizes the current knowledge on the safety and efficacy of various NSAIDs used in infants for which data are available, and includes ibuprofen, dexibuprofen, ketoprofen, flurbiprofen, naproxen, diclofenac, ketorolac, indomethacin, niflumic acid, meloxicam, celecoxib, parecoxib, rofecoxib, acetylsalicylic acid, and nimesulide. The efficacy of NSAIDs has been documented for a variety of conditions, such as fever and pain. NSAIDs are also the main pillars of anti-inflammatory treatment, such as in pediatric inflammatory rheumatic diseases. Limited data are available on the safety of most NSAIDs in infants. Adverse drug reactions may be renal, gastrointestinal, hematological, or immunologic. Since NSAIDs are among the most frequently used drugs in the pediatric population, safety and efficacy studies can be performed as part of normal clinical routine, even in young infants. Available data sources, such as (electronic) medical records, should be used for safety and efficacy analyses. On a larger scale, existing data sources, e.g. adverse drug reaction programs/networks, spontaneous national reporting systems, and electronic medical records should be assessed with child-specific methods in order to detect safety signals pertinent to certain pediatric age groups or disease entities. To improve the safety of NSAIDs in infants, treatment needs to be initiated with the lowest age-appropriate or weight-based dose. Duration of treatment and amount of drug used should be regularly evaluated and maximum dose limits and other recommendations by the manufacturer or expert committees should be followed. Treatment for non-chronic conditions such as fever and acute (postoperative) pain should be kept as short as possible. Patients with chronic conditions should be regularly monitored for possible adverse effects of NSAIDs.

An interview with Dr. Anne Marie Lynn, a pioneering woman in medicine

Dr. Anne Marie Lynn (1949-present), Professor Emeritus of Anesthesiology, Pain Medicine, and Pediatrics at the University of Washington, Seattle, was one of the most influential women in pediatric anesthesiology of her generation. Dr. Lynn embodies the spirit of discovery and advancement that have created the practice of pediatric anesthesiology as we know it today. A pioneer in pain medicine pharmacology, particularly morphine and ketorolac, her research transformed pediatric anesthesia, pediatric pain medicine, and pediatric intensive care medicine. Through her journal articles, book chapters, national and international lectures, mentoring of residents, fellows, and faculty, and leadership in the Society for Pediatric Anesthesia, she inspired a generation of women and men physicians by demonstrating that gender should not be a barrier to undertaking roles once only held only by men. In 2017, for her many contributions, she was awarded the Society for Pediatric Anesthesia's Myron Yaster lifetime achievement award.

Liquid chromatographic enantioseparation, determination, bioassay and isolation of enantiomers of Ketorolac: A review

Ketorolac (Ket) is a potent non-narcotic analgesic drug (among the nonsteroidal anti-inflammatory drugs). The physiological activity of Ket resides with (S)-(−)-Ket while the drug is marketed and administered as a racemic mixture. Therefore, it is desirable that the pharmacokinetics is measured and quantified for enantiomers individually and not as a total drug. The present paper is focused on relevant literature on LC enantioseparation of (RS)-Ket along with bioassay, pharmacokinetic and clinical studies within the discipline of analytical chemistry. HPLC and Thin layer chromatography (TLC) methods using both direct and indirect approaches are discussed. The methods provide chirality recognition even in the absence of pure enantiomers. Besides, a brief discussion on resolution by crystallization and enzymatic methods is included. The most interesting aspects include establishment of structure and molecular asymmetry of diastereomeric derivatives using LC-MS, proton nuclear magnetic resonance spectrometry, and by drawing conformations in three dimensional views by using certain software. A brief discussion has also been provided on the recovery of native enantiomers by TLC.

Safety and Efficacy of Single-Dose Ketorolac for Postoperative Pain Management After Primary Palatoplasty: A Prospective Cohort Study With Historical Controls

OBJECTIVE

To analyze safety and efficacy of single-dose ketorolac after primary palatoplasty (PP).

DESIGN

Consecutive cohort of patients undergoing PP, comparing to historical controls. Setting: A large academic children's hospital.

PATIENTS, PARTICIPANTS

A consecutive cohort of 111 patients undergoing PP (study n = 47) compared to historical controls (n = 64).

INTERVENTIONS

All patients received intraoperative acetaminophen, dexmedetomidine, and opioids while the study group received an additional single dose of ketorolac (0.5 mg/kg) at the conclusion of PP.

MAIN OUTCOME MEASURES

Safety of ketorolac was measured by significant bleeding complications and need for supplementary oxygen. Efficacy was assessed through bleeding, Face Legs Activity Cry Consolability (FLACC) scale, and opioid dose.

RESULTS

Length of stay was similar for both groups (control group 38.5 hours [95% CI: 3.6-43.3] versus study group 37.6 hours [95% CI: 31.3-44.0], P = .84). There were no significant differences in all postoperative FLACC scales. The mean dose of opioid rescue medication measured as morphine milligram equivalents did not differ between groups (P = .56). Significant postoperative hemorrhage was not observed.

CONCLUSIONS

This is the first prospective study to evaluate the safety and efficacy of single-dose ketorolac after PP. Although lack of standardization between study and historical control groups may have precluded observation of an analgesic benefit, analysis demonstrated a single dose of ketorolac after PP is safe. Further investigations with more patients and different postoperative regimens may clarify the role of ketorolac in improving pain after PP.

Ketorolac in Postoperative Neonates and Infants: A Systematic Review

OBJECTIVE

To evaluate the pharmacokinetics and pharmacodynamics, dosing, efficacy, and safety of ketorolac in postoperative patients younger than 6 months of age.

METHODS

PubMed (1988-July 2020), Medline (1946-July 2020), and EBSCO Discovery Service (1988-July 2020) were searched to identify relevant published articles using the following search terms: ketorolac, neonate, infant. English-language articles evaluating the use of ketorolac in infants younger than 6 months of age were included.

RESULTS

Eight reports that included 239 infants receiving ketorolac were included. Of the included patients, 237 were younger than 6 months of age. Ketorolac exhibits rapid elimination of the analgesia-producing S (-) isomer, elimination half-life of 0.83 hours. Most patients received 0.5 mg/kg/dose every 6 hours for 48 to 72 hours. Analgesia was demonstrated by reduced use of open-label morphine and significant lowering of Neonatal/Infant Pain Scale scores. Adverse effects were minimal when ketorolac was used in term neonates and infants without baseline renal dysfunction.

CONCLUSIONS

Randomized placebo-controlled trials of ketorolac use in this population are lacking; however, most published reports noted efficacy and safety with ketorolac in properly selected infants.

Impact of enantiomer-specific changes in pharmacokinetics between infants and adults on the target concentration of racemic ketorolac: A pooled analysis

Aims

Ketorolac is a nonsteroidal anti‐inflammatory racemic drug with analgesic effects only attributed to its S‐enantiomer. The aim of this study is to quantify enantiomer‐specific maturational pharmacokinetics (PK) of ketorolac and investigate if the contribution of both enantiomers to the total ketorolac concentration remains equal between infants and adults or if a change in target racemic concentration should be considered when applied to infants.

Methods

Data were pooled from 5 different studies in adults, children and infants, with 1020 plasma concentrations following single intravenous ketorolac administration. An allometry‐based enantiomer‐specific population PK model was developed with NONMEM 7.3. Simulations were performed in typical adults and infants to investigate differences in S‐ and R‐ketorolac exposure.

Results

S‐ and R‐ketorolac PK were best described with a 3‐ and a 2‐compartment model, respectively. The allometry‐based PK parameters accounted for changes between populations. No maturation function of ketorolac clearance could be identified. All model parameters were estimated with adequate precision (relative standard error <50%). Single dose simulations showed that a previously established analgesic concentration at half maximal effect in adults of 0.37 mg/L, had a mean S‐ketorolac concentration of 0.057 mg/L, but a mean S‐ketorolac concentration of 0.046 mg/L in infants. To match the effective adult S‐ketorolac‐concentration (0.057 mg/L) in typical infants, the EC_50‐racemic should be increased to 0.41 mg/L.

Conclusion

Enantiomer‐specific changes in ketorolac PK yield different concentrations and S‐ and R‐ketorolac ratios between infants and adults at identical racemic concentrations. These PK findings should be considered when studies on maturational pharmacodynamics are considered.

Comparison between epidural and opioid analgesia for infants undergoing major abdominal surgery

BACKGROUND

Epidural analgesia is considered optimal for postoperative pain management after major abdominal surgery. The potential to decrease anesthetic and opioid exposure is particularly desirable for infants, given their vulnerability to respiratory depression and concern for anesthetic neurotoxicity. We reviewed our experience with infants undergoing major abdominal surgery to determine if epidural catheter use decreased anesthetic and opioid exposure and improved postoperative analgesia.

METHODS

This retrospective cohort study included infants (<12 months) who underwent exploratory laparotomy, ureteral reimplantation, or bladder exstrophy repair between November 2011 and November 2014. Primary outcomes of anesthetic exposure (mean endtidal sevoflurane) and intraoperative opioid administration were compared between infants who received epidural catheters and those who did not. Secondary outcomes included postoperative pain and sedation scores and morphine equivalents administered 0-24 and 24-48 hours after surgery.

RESULTS

Of 158 eligible infants, 82 were included and 47 received epidurals. Patients with epidurals underwent bladder exstrophy repair (N = 9), ureteral reimplantation (N = 8), and exploratory laparotomy (N = 30). Infants with epidurals received less intraoperative fentanyl (2.6 mcg/kg (0,4.5) vs 3.3 mcg/kg (2.4,5.8), P = 0.019) and morphine (6% (3/47) vs 26% (9/35), P = 0.014) in univariate analysis. After controlling for age and emergency surgery, differences in long-acting opioid administration persisted, with significantly less morphine given in the epidural group (OR 0.181; 95% CI 0.035-0.925; P = 0.040). Mean endtidal sevoflurane concentrations were similar between groups. There was no significant difference in postoperative median morphine equivalents.

CONCLUSION

Placement of epidural catheters in infants undergoing major abdominal surgery is associated with decreased long-acting opioid requirements intraoperatively. Epidural placement does not preclude opioid exposure however, as opioids may be administered for indications other than nociceptive pain in the difficult-to-assess postoperative infant. Further prospective studies are warranted to better quantify the effect of epidural analgesia on intraoperative anesthetic exposure in infants.

Utilization of data below the analytical limit of quantitation in pharmacokinetic analysis and modeling: promoting interdisciplinary debate

Traditionally, bioanalytical laboratories do not report actual concentrations for samples with results below the LOQ (BLQ) in pharmacokinetic studies. BLQ values are outside the method calibration range established during validation and no data are available to support the reliability of these values. However, ignoring BLQ data can contribute to bias and imprecision in model-based pharmacokinetic analyses. From this perspective, routine use of BLQ data would be advantageous. We would like to initiate an interdisciplinary debate on this important topic by summarizing the current concepts and use of BLQ data by regulators, pharmacometricians and bioanalysts. Through introducing the limit of detection and evaluating its variability, BLQ data could be released and utilized appropriately for pharmacokinetic research.

Narrative review shows that the short-term use of ketorolac is safe and effective in the management of moderate-to-severe pain in children

In June 2013, the European Medicine Agency recommended limiting codeine use in paediatric patients, creating a void in managing moderate pain. We reviewed the literature published in English (1985-June 2017) on the pharmacokinetic, pharmacodynamic and safety profile of ketorolac, a possible substitute for codeine and opioids, for treating moderate-to-severe pain. We found that gastrointestinal side effects were mainly reported with prolonged use, significant bleeding was reported in adenotonsillectomy, and adverse renal effects appeared to be limited to patients with specific coexisting risk factors.

CONCLUSION

The short-term use of ketorolac appears to be safe for children in many situations.

The pharmacokinetics of intravenous ketorolac in children aged 2 months to 16 years: A population analysis

BACKGROUND

Intravenous ketorolac is commonly administered to children for the control of postoperative pain. An effect site EC₅₀ for analgesia of 0.37 mg^. L^-1 is described in adults.

AIMS

The aim of this study was to review age- and weight-related effects on ketorolac pharmacokinetic parameters in children and current dosing schedules.

METHODS

Pooled intravenous ketorolac (0.5 mg^. kg^-1 ) concentration-time data in children aged 2 months to 16 years were analyzed using nonlinear mixed-effects models. Allometry was used to scale to a 70 kg person.

RESULTS

There were 64 children aged 2 months to 16 years (641 plasma concentrations) available for analysis. A two-compartment mammillary model was used to describe pharmacokinetics. Clearance was 2.53 (CV 45.9%) L^. h^-1. 70 kg^-1 and intercompartment clearance was 4.43 (CV 95.6%) L^. h^-1. 70 kg^-1 . Both central (V1) and peripheral (V2) volumes of distribution decreased with age over the first few years of postnatal life to reach V1 6.89 (CV 30.3%) L^. 70 kg^-1 and V2 5.53 (CV 47.6%) L^. 70 kg^-1 .

CONCLUSION

Clearance, expressed as L^. h^-1. kg^-1 , decreased with age from infancy. A dosing regimen of 0.5 mg^. kg^-1 every 6 hours maintains a trough concentration larger than 0.37 mg^. L^-1 in children 9 months to 16 years of age. This dosing regimen is consistent with current recommendations.

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.

A review of perioperative anesthesia and analgesia for infants: updates and trends to watch

This review focuses on pharmacokinetics and pharmacodynamics of opioid and non-opioid analgesics in neonates and infants. The unique physiology of this population differs from that of adults and impacts drug handling. Morphine and remifentanil are described as examples of older versus recently developed opiates to compare and contrast pharmacokinetics and pharmacodynamics in infants. Exploration of genetics affecting both pharmacokinetics and pharmacodynamics of opiates is an area of active research, as is the investigation of a new class of mu-opiate-binding agents which seem selective for analgesic pathways while having less activity in pathways linked to side effects. The kinetics of acetaminophen and of ketorolac as examples of parenteral non-steroidal analgesics in infants are also discussed. The growth in regional anesthesia for peri-operative analgesia in infants can fill an important role minimizing intra-operative anesthetic exposure to opioids and transitioning to post-operative care. Use of multi-modal techniques is recommended to decrease undesirable opiate-related side effects in this vulnerable population.

A retrospective comparison of ropivacaine and 2-chloroprocaine continuous thoracic epidural analgesia for management of postthoracotomy pain in infants

INTRODUCTION

Continuous thoracic epidural analgesia is useful in the management of infants following thoracotomy. Concerns about drug accumulation and toxicity limit the amount of amide local anesthetics that can be delivered. Continuous epidural infusions of the ester local anesthetic chloroprocaine result in little drug accumulation allowing for higher infusion rates. We retrospectively compared patients managed with 1.5% 2- chloroprocaine or 0.1% ropivacaine epidural infusions to determine if the increased infusion rate resulted in similar or improved analgesia.

METHODS

This retrospective cohort comparison consisted of full term infants 6 months or younger who underwent thoracotomy for congenital lung lesion resection. Patients were included if they were managed with either a 1.5% 2-chloroprocaine (Group C) (n = 26) or 0.1% ropivacaine (Group R) (n = 28) infusion administered through a caudally placed thoracic epidural catheter. The primary outcome was morphine administration at 0-24 h.

RESULTS

Patients were similar in age, weight, length of stay, epidural location and duration. There was weak evidence for a difference in morphine use in the first 24 h in Group C compared to Group R (P = 0.08) but no difference 24-48 h. Group C was more commonly managed with ketorolac at 0-24 h (P = 0.03) and 24-48 h (P =< 0.01).

DISCUSSION

The use of 2-chloroprocaine for continuous epidural infusion in infants following thoracotomy was not inferior to ropivacaine and there was weak evidence for a reduction in opioid consumption in the first 24 h postoperatively. However, the 2-chloroprocaine group was more likely to receive ketorolac.

The enantioselective population pharmacokinetics of intravenous ketorolac in children using a stereoselective assay suitable for microanalysis†

Objective

To describe the effect of age and body size on enantiomer selective pharmacokinetic (PK) of intravenous ketorolac in children using a microanalytical assay.

Methods

Blood samples were obtained at 0, 15 and 30 min and at 1, 2, 4, 6, 8 and 12 h after a weight-dependent dose of ketorolac. Enantiomer concentration was measured using a liquid chromatography tandem mass spectrometry method. Non-linear mixed-effect modelling was used to assess PK parameters.

Key findings

Data from 11 children (1.7–15.6 years, weight 10.7–67.4 kg) were best described by a two-compartment model for R(+), S(−) and racemic ketorolac. Only weight (WT) significantly improved the goodness of fit. The final population models were CL = 1.5 × (WT/46)0.75, V1 = 8.2 × (WT/46), Q = 3.4 × (WT/46)0.75, V2 = 7.9 × (WT/46), CL = 2.98 × (WT/46), V1 = 13.2 × (WT/46), Q = 2.8 × (WT/46)0.75, V2 = 51.5 × (WT/46), and CL = 1.1 × (WT/46)0.75, V1 = 4.9 × (WT/46), Q = 1.7 × (WT/46)0.75 and V2 = 6.3 × (WT/46)for R(+), S(−) and racemic ketorolac.

Conclusions

Only body weight influenced the PK parameters for R(+) and S(−) ketorolac. Using allometric size scaling significantly affected the clearances (CL, Q) and volumes of distribution (V1, V2).

Effects of COX inhibition and LPS on formalin induced pain in the infant rat

In the adult, immune and neural processes jointly modulate pain. During development, both are in transition and little is known about the role that the immune system plays in pain processing in infants and children. The objective of this study was to determine if inhibition or augmentation of the immune system would alter pain processing in the infant rat, as it does in the adult. In Experiment 1, rat pups aged 3, 10, or 21 (PN3, PN10, and PN21) days of age were pretreated with NS398 (selective cyclooxygenase (COX)-2 inhibitor) or SC560 (selective COX-1 inhibitor) and tested in the intraplantar formalin test to assess effects of COX inhibition on nociception. Neither drug had an effect on the behavioral response at PN3 or PN10 pups but both drugs attenuated nociceptive scores in PN21 pups. cFos expression in the spinal cord likewise was reduced only at PN21. In Experiment 2, pups were injected with lipopolysaccharide (LPS) prior to the formalin test at PN3 or PN21. LPS increased the nociceptive response more robustly at PN21 than at PN3, while increasing cytokine mRNA equally at both ages. The augmentation of pain responding at PN21 was largely during the late stages of the formalin test, as reported in the adult. These data support previous findings demonstrating late maturing immune modulation of nociceptive behaviors.

Suprachoroidal injection of ketorolac tromethamine does not cause retinal damage

Rabbit right eyes were injected with 3 or 6 mg ketorolac tromethamine into the suprachoroidal space. Electroretinography results demonstrated no abnormal changes in rod cell response, maximum rod cell or cone cell mixing reaction, oscillation potential, cone cell response, waveform, amplitude, and potential of 30 Hz scintillation response in right eyes before injection, and at 1, 2, and 4 weeks after injection. There was no difference between left (control) and right eyes. Under light microscopy, the histomorphology of cells in each retinal layer was normal at 4 weeks following 6 mg ketorolac tromethamine administration. These results indicate that a single suprachoroidal injection of 3 or 6 mg ketorolac tromethamine into rabbits was safe. Suprachoroidal space injection appears to be safe.