Ibuprofen for acute postoperative pain in children

BACKGROUND

Children often require pain management following surgery to avoid suffering. Effective pain management has consequences for healing time and quality of life. Ibuprofen, a frequently used non-steroidal anti-inflammatory drug (NSAID) administered to children, is used to treat pain and inflammation in the postoperative period.

OBJECTIVES

1) To assess the efficacy and safety of ibuprofen (any dose) for acute postoperative pain management in children compared with placebo or other active comparators. 2) To compare ibuprofen administered at different doses, routes (e.g. oral, intravenous, etc.), or strategies (e.g. as needed versus as scheduled).

SEARCH METHODS

We used standard Cochrane search methods. We searched CENTRAL, MEDLINE, Embase, CINAHL and trials registries in August 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in children aged 17 years and younger, treated for acute postoperative or postprocedural pain, that compared ibuprofen to placebo or any active comparator. We included RCTs that compared different administration routes, doses of ibuprofen and schedules.

DATA COLLECTION AND ANALYSIS

We adhered to standard Cochrane methods for data collection and analysis. Our primary outcomes were pain relief reported by the child, pain intensity reported by the child, adverse events, and serious adverse events. We present results using risk ratios (RR) and standardised mean differences (SMD), with the associated confidence intervals (CI). We used GRADE to assess the certainty of the evidence.

MAIN RESULTS

We included 43 RCTs that enroled 4265 children (3935 children included in this review). We rated the overall risk of bias at the study level as high or unclear for 37 studies that had one or several unclear or high risk of bias judgements across the domains. We judged six studies as having a low risk of bias across all domains. Ibuprofen versus placebo (35 RCTs) No studies reported pain relief reported by the child or a third party, or serious adverse events. Ibuprofen probably reduces child-reported pain intensity less than two hours postintervention compared to placebo (SMD -1.12, 95% CI -1.39 to -0.86; 3 studies, 259 children; moderate-certainty evidence). Ibuprofen may reduce child-reported pain intensity, two hours to less than 24 hours postintervention (SMD -1.01, 95% CI -1.24 to -0.78; 5 studies, 345 children; low-certainty evidence). Ibuprofen may result in little to no difference in adverse events compared to placebo (RR 0.79, 95% CI 0.51 to 1.23; 5 studies, 384 children; low-certainty evidence). Ibuprofen versus paracetamol (21 RCTs) No studies reported pain relief reported by the child or a third party, or serious adverse events. Ibuprofen likely reduces child-reported pain intensity less than two hours postintervention compared to paracetamol (SMD -0.42, 95% CI -0.82 to -0.02; 2 studies, 100 children; moderate-certainty evidence). Ibuprofen may slightly reduce child-reported pain intensity two hours to 24 hours postintervention (SMD -0.21, 95% CI -0.40 to -0.02; 6 studies, 422 children; low-certainty evidence). Ibuprofen may result in little to no difference in adverse events (0 events in each group; 1 study, 44 children; low-certainty evidence). Ibuprofen versus morphine (1 RCT) No studies reported pain relief or pain intensity reported by the child or a third party, or serious adverse events. Ibuprofen likely results in a reduction in adverse events compared to morphine (RR 0.58, 95% CI 0.40 to 0.83; risk difference (RD) -0.25, 95% CI -0.40 to -0.09; number needed to treat for an additional beneficial outcome (NNTB) 4; 1 study, 154 children; moderate-certainty evidence). Ibuprofen versus ketorolac (1 RCT) No studies reported pain relief or pain intensity reported by the child, or serious adverse events. Ibuprofen may result in a reduction in adverse events compared to ketorolac (RR 0.51, 95% CI 0.27 to 0.96; RD -0.29, 95% CI -0.53 to -0.04; NNTB 4; 1 study, 59 children; low-certainty evidence).

AUTHORS' CONCLUSIONS

Despite identifying 43 RCTs, we remain uncertain about the effect of ibuprofen compared to placebo or active comparators for some critical outcomes and in the comparisons between different doses, schedules and routes for ibuprofen administration. This is largely due to poor reporting on important outcomes such as serious adverse events, and poor study conduct or reporting that reduced our confidence in the results, along with small underpowered studies. Compared to placebo, ibuprofen likely results in pain reduction less than two hours postintervention, however, the efficacy might be lower at two hours to 24 hours. Compared to paracetamol, ibuprofen likely results in pain reduction up to 24 hours postintervention. We could not explore if there was a different effect in different kinds of surgeries or procedures. Ibuprofen likely results in a reduction in adverse events compared to morphine, and in little to no difference in bleeding when compared to paracetamol. We remain mostly uncertain about the safety of ibuprofen compared to other drugs.

Relationship between Pharmacokinetic Profile and Clinical Efficacy Data of Three Different Forms of Locally Applied Flurbiprofen in the Mouth/Throat

This study aimed to link pharmacokinetic (PK) data from different flurbiprofen preparations for the treatment of sore throat with published data to elucidate whether early efficacy is due to the local action of flurbiprofen or a systemic effect after absorption of the swallowed drug. Three comparative bioavailability studies conducted in healthy subjects provided data from flurbiprofen 8.75 mg formulations, including spray solution, spray gel, lozenges, and granules. A parallel interstudy comparison was made of PK parameters, including partial AUCs (pAUCs), using an ANOVA model with the calculation of 90% confidence intervals (CI) for the differences between least squares (LS) means for each of the test groups versus the respective reference groups. All three studies showed bioequivalence for the respective product comparisons. The interstudy comparison showed a slower rate of absorption for granules compared to spray solution (reference) based on T_max, C_max, and pAUCs for 1 h and 2 h. When AUC_0.25h and AUC_0.5h were considered, slower rates of absorption were also seen for lozenges and spray gel. The differences correlated with the reported time of onset of action, which is faster for the spray solution (20 min) compared to lozenges (26 min) and granules (30 min). These pAUCs provide useful data that allow for the discrimination between formulations. Moreover, the pAUC values represent <5% of the total AUC, suggesting that the early onset of pain relief is a response to immediate local absorption at the site of action rather than a systemic effect.

Modeling adult COX-2 cerebrospinal fluid pharmacokinetics to inform pediatric investigation

AIM

Hysteresis is reported between plasma concentration and analgesic effect from nonsteroidal anti-inflammatory drugs. It is possible that the temporal delay between plasma and CSF nonsteroidal anti-inflammatory drugs mirrors this hysteresis. The temporal relationship between plasma and CSF concentrations of COX-inhibitors (celecoxib, rofecoxib, valdecoxib) has been described. The purpose of this secondary data analysis was to develop a compartmental model for plasma and CSF disposition of these COX-2 inhibitors.

METHODS

Plasma and CSF concentration-time profiles and protein binding data in 10 adult volunteers given oral celecoxib 200 mg, valdecoxib 40 mg and rofecoxib 50 mg were available for study. Nonlinear mixed effects models with a single plasma compartment were used to link a single CSF compartment with a transfer factor and an equilibration rate constant (Keq). To enable predictive modeling in pediatrics, celecoxib pharmacokinetics were standardized using allometry.

RESULTS

Movement of all three unbound plasma COX-2 drugs into CSF was characterized by a common equilibration half-time (T_1/2 keq) of 0.84 h. Influx was faster than efflux and a transfer scaling factor of 2.01 was required to describe conditions at steady-state. Estimated celecoxib clearance was 49 (95% CI 34-80) L/h/70 kg and the volume of distribution was 346 (95% CI 237-468) L/70 kg. The celecoxib absorption half-time was 0.35 h with a lag time of 0.62 h. Simulations predicted a 70-kg adult given oral celecoxib 200 mg with maintenance 100 mg twice daily would have a mean steady-state total (bound and unbound) plasma concentration of 174 μg L^-1 and CSF concentration of 1.1 μg L^-1 . A child (e.g., 25 kg, typically 7 years) given oral celecoxib 6 mg kg^-1 with maintenance of 3 mg kg^-1 twice daily would have 282 and 1.7 μg L^-1 mean plasma and CSF concentrations, respectively.

CONCLUSIONS

Transfer of unbound COX-2 inhibitors from plasma to CSF compartment can be described with a delayed effect model using an equilibration rate constant to collapse observed hysteresis. An additional transfer factor was required to account for passage across the blood-brain barrier. Use of a target concentration strategy for dose and consequent plasma (total and unbound) and CSF concentration prediction could be used to inform pediatric clinical studies.

A target concentration strategy to determine ibuprofen dosing in children

BACKGROUND

Ibuprofen is widely used for ductus arteriosus closure in premature neonates and for analgesia in children and adults. There are no maturation descriptors of clearance. This lack of maturation understanding limits dosing recommendations from premature neonates to adulthood.

METHODS

Published clearance estimates from different aged patients determined after administration from time-concentration profiles were used to construct a maturation model based on size and age. Curve fitting was performed using nonlinear mixed-effects models. A target concentration strategy was used to estimate maintenance dose at different ages.

RESULTS

There were three publications reporting an estimate of individual clearance estimates in premature neonates, three reporting population clearances in infants, 11 in children 2-15 years (1 with individual and 9 with population clearances), and 13 adult studies (1 with individual and 12 with population clearances). Clearance maturation, standardized to a 70 kg person was described using the Hill equation. Mature clearance was 3.81 (CV 15.5%, 95%CI 3.72, 3.92) L/h/70 kg. The maturation half-time was 36.8 (CV 9.2%, 95%CI 34.7, 40.9) weeks postmenstrual age and the Hill coefficient 11.5 (95%CI 8.1, 15). A target effect of four units (visual analogue scale 0-10) correlated with an effect site concentration of 6.3 mg/L: a concentration achieved at trough after 400 mg 8 hourly in adults.

CONCLUSION

Previously published pharmacokinetic parameters can be used to develop maturation models that address gaps in current knowledge regarding the influence of age on a drug's disposition. Maturation of ibuprofen clearance was rapid and was 90% of adult values by the first month of life in term neonates (ie, 44 weeks postmenstrual age) and 98% of standardized adult estimates by 3 months of age (53 weeks postmenstrual age). Clearance informed dosing predictions in all ages (premature neonate to adult) and matched those doses in common use in children older than 3 months.

Application of the relationship between pharmacokinetics and pharmacodynamics in drug development and therapeutic equivalence: a PEARRL review

Objectives

The objective of this review was to provide an overview of pharmacokinetic/pharmacodynamic (PK/PD) models, focusing on drug-specific PK/PD models and highlighting their value added in drug development and regulatory decision-making.

Key findings

Many PK/PD models, with varying degrees of complexity and physiological understanding have been developed to evaluate the safety and efficacy of drug products. In special populations (e.g. paediatrics), in cases where there is genetic polymorphism and in other instances where therapeutic outcomes are not well described solely by PK metrics, the implementation of PK/PD models is crucial to assure the desired clinical outcome. Since dissociation between the pharmacokinetic and pharmacodynamic profiles is often observed, it is proposed that physiologically based pharmacokinetic and PK/PD models be given more weight by regulatory authorities when assessing the therapeutic equivalence of drug products.

Summary

Modelling and simulation approaches already play an important role in drug development. While slowly moving away from ‘one-size fits all’ PK methodologies to assess therapeutic outcomes, further work is required to increase confidence in PK/PD models in translatability and prediction of various clinical scenarios to encourage more widespread implementation in regulatory decision-making.

Acetaminophen, ibuprofen, and tramadol analgesic interactions after adenotonsillectomy

BACKGROUND

The impact of tramadol in children given acetaminophen-ibuprofen combination therapy is uncertain in acute pediatric pain management. A model describing the interaction between these three drugs would be useful to understand the role of supplemental analgesic therapy.

METHODS

Children undergoing tonsillectomy were given oral paracetamol and ibuprofen perioperatively. Blood was taken for paracetamol and ibuprofen drug assay on up to six occasions over 6 h after the initial dose. Tramadol was administered by caregivers for unacceptable postoperative pain. Pain was measured using the Parent's Postoperative Pain Measurement rating two hourly on the first postoperative day. A first-order absorption, one-compartment linear model with first-order elimination was used to describe acetaminophen and ibuprofen disposition. Analgesia was described using an E_MAX model extended for three drugs, assuming additive effects. Curve fitting was performed using nonlinear mixed effects models.

RESULTS

Pharmacodynamic parameter estimates, expressed using fractional Hill equation, were maximum effect (E_MAX ) 0.65 (95%CI 0.54, 0.74), the concentration of acetaminophen associated with 50% of the maximal drug effect (C_50,ACET ) 7.06 (95%CI 7.03, 7.72) mg/L, and the ibuprofen C₅₀ (C_50,IBU ) 3.95 (95%CI 2.57, 7.53) mg/L. The Hill coefficient was 1.48 (95%CI 0.92, 2.62) and an interaction term was fixed at zero (additivity). The half-time (t_1/2 keo) for equilibration between the plasma and effect site was 0.34 hour (95%CI 0.23, 1.98) for acetaminophen and 1.04 hour (95%CI 0.75, 1.77) for ibuprofen. Tramadol had a C_50,TRAM of 0.07 (95%CI 0.048, 1.07) mg/L with a t_1/2 keo,_TRAM 1.78 hour (95%CI 1.06, 1.96).

CONCLUSION

Ibuprofen has an EC₅₀ for analgesia in children similar to that of adults (3.95 mg/L; 95%CI 2.57-7.53, vs 5-10 mg/L adults). The maximum effect from combination therapy (ie, 65% reduction in pain score) achieves satisfactory analgesia with commonly used doses but increased dose adds little additional benefit. The addition of tramadol to this analgesic mixture prolongs analgesia duration.

Pharmacokinetics and analgesic effectiveness of intravenous parecoxib for tonsillectomy ± adenoidectomy

BACKGROUND

Few pharmacokinetic (PK) and pharmacodynamic (PD) data exist for COX-2 selective inhibitors in children. We wished to characterize the PKPD of parecoxib and its active metabolite, valdecoxib, in this population.

METHODS

Children (n = 59) were randomized to parecoxib 0.25 mg·kg^-1 , 1 mg·kg^-1 , and 2 mg·kg^-1 during tonsillectomy ± adenoidectomy. Samples (4-6 per child) were obtained from indwelling cannula over 6 h. A second group of inpatient children (n = 15) given 1 mg·kg^-1 contributed PK data from 6 to 24 h. Pain scores and rescue medication for the first group were recorded postoperatively for up to 24 h. PK data were pooled with those (10 samples/24 h) from a published study of children (n = 38) who underwent surgery. A three-compartment parent and one-compartment metabolite model with first-order elimination was used to describe data using nonlinear mixed effects models. An E_MAX model described the relationship between dose and rescue morphine equivalents during recovery.

RESULTS

Parecoxib PK parameter estimates were CL_PARECOXIB 19.1 L·h^-1 ·70 kg^-1 , V1_PARECOXIB 4.2 L·70 kg^-1 , Q2_PARECOXIB 6.29 L·h^-1 ·70 kg^-1 , V2_PARECOXIB 130 L·70 kg^-1 , Q3_PARECOXIB 6.02 L·h^-1 ·70 kg^-1 , and V3_PARECOXIB 2.03 L·70 kg^-1 . We assumed all parecoxib was metabolized to valdecoxib with CL_VALDECOXIB 9.53 L·h^-1 ·70 kg^-1 and V_VALDECOXIB 51 L·70 kg^-1 . There was no maturation of clearance over the age span studied. There were no differences in pain scores between groups on waking, discharge, 12 h, or 24 h. There were no differences in analgesia consumption over 24 h between groups for tramadol, fentanyl, and morphine rescue use. Fentanyl and morphine consumption, expressed as morphine equivalents (0.13 mg·kg^-1 ) in the 0.25 mg·kg^-1 group, was greater than that observed in the 1 or 2 mg·kg^-1 groups (0.095 mg·kg^-1 ) in PACU.

CONCLUSIONS

Parecoxib 0.9 mg·kg^-1 in a 2-year-old, 0.75 mg·kg^-1 in a 7-year-old, and 0.65 mg·kg^-1 in a 12-year-old child achieves dose equivalence of 40 mg in a standard 70 kg person. Clearance maturation may occur in infants younger than the current cohort. Parecoxib doses above 1 mg·kg^-1 add no additional analgesia.

Ibuprofen sodium is absorbed faster than standard Ibuprofen tablets: results of two open-label, randomized, crossover pharmacokinetic studies

Background

A novel ibuprofen (IBU) formulation, Advil^® Film-Coated Tablets (IBU_Na), was developed.

Objective

Pharmacokinetic comparison of IBU_Na versus other IBU formulations.

Study Design

Two randomized, single-dose, open-label, five-way crossover pharmacokinetic studies.

Setting

Inpatient research clinic.

Subjects

Seventy-one healthy adult volunteers.

Intervention

Study 1: In three periods, fasted subjects received 400-mg IBU dose equivalents as IBU_Na 2 × 256 mg, Advil^® Liqui-Gels^® (IBU_LG) 2 × 200 mg, and Motrin^® IB (IBU_Mot) 2 × 200 mg tablets. In two periods following a high-fat breakfast, subjects received 400-mg IBU dose equivalents as IBU_Na 2 × 256 mg and IBU_LG 2 × 200 mg. Study 2: In five study periods, fasted subjects received 400-mg IBU dose equivalents as IBU_Na 2 × 256 mg, Advil^® FastGel^® (IBU_FG) 2 × 200 mg, Nurofen^® (IBU_Nur) 2 × 200 mg, Advil^® (IBU_Adv) 2 × 200 mg, and Nurofen^® Express containing IBU lysinate (IBU_Lys) 2 × 342 mg.

Main Outcome Measure

Log-transformed area under the plasma concentration versus time curve to last observable concentration (AUC_L) and maximum plasma concentration (C_max) were the primary pharmacokinetic parameters; time to maximum measured plasma concentration (T_max) was analyzed post hoc.

Results

IBU_Na was bioequivalent to IBU_LG (fasted and fed) and IBU_FG and IBU_Lys (fasted) for rate (C_max) and extent (AUC_L) of IBU absorption. After fasting, AUC_L was bioequivalent for IBU_Na and IBU_Mot, IBU_Adv, and IBU_Nur, but C_max occurred significantly earlier with IBU_Na. After fasting, median IBU_NaT_max was comparable to that for IBU_LG, IBU_FG, and IBU_Lys, but was much shorter than that for IBU_Mot, IBU_Nur, and IBU_Adv. Food slowed absorption of IBU_Na and IBU_LG similarly. All treatments were tolerated similarly.

Conclusion

IBU_Na is absorbed faster but to a similar extent as standard IBU formulations.

Considerations when using pharmacokinetic/pharmacodynamic modeling to determine the effectiveness of simple analgesics in children

INTRODUCTION

Assessment of analgesic drugs includes comparative studies to other analgesics and local anesthesia blockade, number needed to treat estimates and opioid sparing descriptions. An additional methodology is to define the concentration-response relationship using pharmacokinetic/pharmacodynamic (PK/PD) modeling.

AREAS COVERED

A concentration-response relationship allows analgesic effect comparison between drugs for different acute pain types. Covariates such as size, age and organ function impact greatly on PK in children. The cumulative effect of confounding factors (e.g., pharmacogenetics, placebo and changes in baseline pain over time) complicates PD. Other factors (outcome measures, method of measurement, failure to account for study attrition) impact on outcome. Population PK/PD modeling approaches allow us to account for these various factors to some extent.

EXPERT OPINION

Nonlinear mixed effects models help interpret analgesic data and their use is increasing. The PK is relatively well understood. The next investigative step will involve investigation into covariate effects for PD. Mathematical functions for both placebo models and dropout models are well described and should be incorporated into analgesic effectiveness studies that investigate a range of doses. Improvements in pain assessment tools and a greater understanding of pharmacogenomics factors will help individualize analgesic therapy.

Prophylactic ibuprofen does not improve pain with IUD insertion: a randomized trial

OBJECTIVE

To evaluate if ibuprofen 800mg reduces pain with intrauterine device (IUD) insertion among U.S. women.

STUDY DESIGN

We conducted a randomized, double-blind, placebo-controlled trial of women undergoing IUD insertion approximately 2-6weeks following first-trimester uterine aspiration. Subjects were randomized to receive ibuprofen 800mg or placebo 30-45min prior to IUD insertion. A 100-mm visual analog scale (VAS) was administered to measure pain after speculum insertion (baseline) and immediately following IUD insertion.

RESULTS

A total of 202 women were enrolled, with 101 randomized to each group (ibuprofen or placebo). Sociodemographic characteristics and baseline VAS scores were similar between groups. The median pain score with IUD insertion was 41.5mm in the placebo group and 38.0mm in the ibuprofen group (p=.50). Mean and median pain scores did not differ between placebo and ibuprofen when nulliparous and parous women were analyzed independently. Overall, median pain scores were 17.5mm higher in nulliparous women than parous women (p=.004). Median pain scores did not differ by age, IUD-type, history of dysmenorrhea or time since aspiration.

CONCLUSIONS

Administration of ibuprofen 800mg prior to IUD insertion does not reduce pain associated with the procedure for U.S. women. Overall, nulliparous women report more pain with IUD insertion than multiparous women.

Postoperative analgesia using diclofenac and acetaminophen in children

BACKGROUND

Diclofenac dosing in children for analgesia is currently extrapolated from adult data. Oral diclofenac 1.0 mg·kg(-1) is recommended for children aged 1-12 years. Analgesic effect from combination diclofenac/acetaminophen is unknown.

METHODS

Children (n = 151) undergoing tonsillectomy (c. 1995) were randomized to receive acetaminophen elixir 40 mg·kg(-1) before surgery and 20 mg·kg(-1) rectally at the end of surgery with diclofenac suspension 0.1 mg·kg(-1) , 0.5 mg·kg(-1) , or 2.0 mg·kg(-1) before surgery or placebo. A further 93 children were randomized to receive diclofenac 0.1 mg·kg(-1) , 0.5 mg·kg(-1) , or 2.0 mg·kg(-1) only. Postoperative pain was assessed (visual analogue score, VAS 0-10) at half-hourly intervals from waking until discharge. Data were pooled with those from a further 222 children and 30 adults. One-compartment models with first-order absorption and elimination described the pharmacokinetics of both medicines. Combined drug effects were described using a modified EMAX model with an interaction term. An interval-censored model described the hazard of study dropout.

RESULTS

Analgesia onset had an equilibration half-time of 0.496 h for acetaminophen and 0.23 h for diclofenac. The maximum effect (EMAX ) was 4.9. The concentration resulting in 50% of EMAX (C50 ) was 1.23 mg·l(-1) for diclofenac and 13.3 mg·l(-1) for acetaminophen. A peak placebo effect of 6.8 occurred at 4 h. Drug effects were additive. The hazard of dropping out was related to pain (hazard ratio of 1.35 per unit change in pain). Diclofenac 1.0 mg·kg(-1) with acetaminophen 15 mg·kg(-1) achieves equivalent analgesia to acetaminophen 30 mg·kg(-1) .

CONCLUSIONS

Combination therapy can be used to achieve similar analgesia with lower doses of both drugs.

Faster, higher, stronger? Evidence for formulation and efficacy for ibuprofen in acute pain

A Cochrane review of ibuprofen in acute pain suggested that rapidly absorbed formulations of salts, or features to speed absorption, provided better analgesia than standard ibuprofen as the free acid. We examined several lines of evidence to investigate what benefit derived from fast-acting formulations. A systematic review of the kinetics of oral ibuprofen (30 studies, 1015 subjects) showed that median maximum plasma concentrations of fast-acting formulations occurred before 50 min (29-35 min for arginine, lysine, and sodium salts) compared with 90 min for standard formulations. An updated analysis of clinical trials (over 10,000 patients) showed that fast-acting formulations produced significantly better analgesia over 6h and fewer remedications than standard formulations in both indirect and direct comparisons. In dental studies, 200-mg fast-acting ibuprofen (number needed to treat 2.1; 95% confidence interval 1.9-2.4) was as effective as 400 mg standard ibuprofen (number needed to treat 2.4; 95% confidence interval 2.2-2.5), with faster onset of analgesia. Individual patient data analysis in dental pain demonstrated a strong correlation between more rapid reduction of pain intensity over 0-60 min and better pain relief over 0-6h. Rapid initial reduction of pain intensity was also linked with reduced need for remedication. Fast-acting formulations of ibuprofen demonstrated more rapid absorption, faster initial pain reduction, good overall analgesia in more patients at the same dose, and probably longer-lasting analgesia, but with no higher rate of patients reporting adverse events. Achieving a better analgesic effect with fast-acting nonsteroidal anti-inflammatory drug formulations has important implications for safety. Formulation chemistry is of potential importance for analgesics.

Efficacy and safety of low dose subcutaneous diclofenac in the management of acute pain: a randomized double-blind trial

OBJECTIVE

Diclofenac is an effective and well-tolerated nonsteroidal anti-inflammatory drug (NSAID) frequently used in the treatment of acute pain. Marketed formulations for parenteral administration usually contain 75 mg/3 mL of diclofenac sodium, which provide limited dosing flexibility, and are usually given intramuscularly.

METHODS

We present a randomized, double-blind, active comparator- and placebo-controlled, parallel-group phase III multicenter study, investigating efficacy and tolerability of a new 1 mL-volume formulation of diclofenac sodium (25, 50 or 75 mg) containing hydroxypropyl-β-cyclodextrin (HPβCD) as a solubility enhancer. This low-volume formulation allows subcutaneous (SC), in addition to intramuscular (IM) administration. Patients developing moderate-to-severe pain (≥ 50 mm on Visual Analogue Scale) after third molar extraction under local anesthesia were randomized to one of the 4 SC injections: 25 mg diclofenac HPβCD (n = 77), 50 mg diclofenac HPβCD (n = 76), 75 mg diclofenac HPβCD (n = 78), or placebo (n = 75).

RESULTS

Mean pain intensity difference at 1.5 hours postdose (primary endpoint) was higher in all diclofenac-treated groups than placebo group. The adjusted means (95% CI) were 36.5 (31.7 to 41.2) in diclofenac 25 mg group, 37.3 (32.6 to 42.1) in diclofenac 50 mg group, 37.7 (33.0 to 42.4) in diclofenac 75 mg group, and 12.3 (7.44 to 17.1) in placebo group. Both 25 and 50 mg doses of diclofenac produced significantly greater pain relief than placebo (P < 0.001 in both comparisons).

CONCLUSION

Single SC doses of diclofenac HPβCD of 25 and 50 mg are effective and well tolerated for relieving pain compared with placebo.

Translational PK-PD modeling in pain

The current gap between animal research and clinical development of analgesic drugs presents a challenge for the application of translational PK-PD modeling and simulation. First, animal pain models lack predictive and construct validity to accurately reflect human pain etiologies and, secondly, clinical pain is a multidimensional sensory experience that can't always be captured by objective and robust measures. These challenges complicate the use of translational PK-PD modeling to project PK-PD data generated in preclinical species to a plausible range of clinical doses. To date only a few drug targets identified in animal studies have shown to be successful in the clinic. PK-PD modeling of biomarkers collected during the early phase of clinical development can bridge animal and clinical pain research. For drugs with novel mechanism of actions understanding of the target pharmacology is essential in order to increase the success of clinical development. There is a specific interest in the application of human pain models that can mimic different aspects of acute/chronic pain symptoms and serves as link between animal and clinical pain research. In early clinical development the main objective of PK-PD modeling is to characterize the relationship between target site binding and downstream biomarkers that have a potential link to the clinical endpoint (e.g. readouts from the human pain models) so as to facilitate the selection of doses for proof of concept studies. In patient studies, the role of PK-PD modeling and simulation is to characterize and confirm patient populations in terms of responder profiles with the aim to find the right dose for the right patient.