The pharmacokinetics of a high intravenous dose of paracetamol after caesarean delivery: the effect of gestational age

Intravenous acetaminophen for postoperative pain control after open abdominal and thoracic surgery in pediatric patients: a systematic review and meta-analysis

Pediatric opioid exposure increases short- and long-term adverse events (AE). The addition of intravenous acetaminophen (IVA) to pediatric pain regimes to may reduce opioids but is not well studied postoperatively. Our objective was to quantify the impact of IVA on postoperative pain, opioid use, and AEs in pediatric patients after major abdominal and thoracic surgery. Medline, Embase, CINAHL, Web of Science, and Cochrane Library were searched systematically for randomized controlled trials (RCTs) comparing IVA to other modalities. Five RCTs enrolling 443 patients with an average age of 2.12 years (± 2.81) were included. Trials comparing IVA with opioids to opioids alone were meta-analyzed. Low to very low-quality evidence demonstrated equivalent pain scores between the groups (-0.23, 95% CI -0.88 to 0.40, p 0.47) and a reduction in opioid consumption (-1.95 morphine equivalents/kg/48 h, 95% CI -3.95 to 0.05, p 0.06) and minor AEs (relative risk 0.39, 95% CI 0.11 to 1.43, p 0.15). We conclude that the addition of IVA to opioid-based regimes in pediatric patients may reduce opioid use and minor AEs without increasing postoperative pain. Given the certainty of evidence, further research featuring patient-important outcomes and prolonged follow-up is necessary to confirm these findings.

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.

Single-dose systemic acetaminophen to prevent postoperative pain: a meta-analysis of randomized controlled trials

OBJECTIVES

The effect of a single-dose systemic acetaminophen to treat postoperative pain has been previously quantified, but the effect of systemic acetaminophen to prevent postoperative pain is currently not well defined. The preventive analgesic effect of acetaminophen has yet to be quantified in a meta-analysis. The objective of the current investigation was to evaluate the effect of a single preventive dose of systemic acetaminophen on postoperative pain outcomes.

MATERIALS AND METHODS

A wide search was performed to identify randomized controlled trials that evaluated the effects of a single dose of systemic acetaminophen on pain outcomes in a large variety of surgical procedures. Meta-analysis was performed using a random-effect model.

RESULTS

Eleven randomized clinical trials evaluating 740 patients were included in the analysis. The weighted mean difference (95% confidence interval [CI]) of the combined effects favored acetaminophen over control for early pain at rest (≤4 h, -1.1 (-2.0 to -0.2)) and early pain at movement (24 h, -1.9 (-2.8 to -1.0)) Postoperative opioid consumption was decreased in the systemic acetaminophen group compared with control. Weighted mean difference (95% CI) of -9.7 (-13.0 to -6.4) mg morphine intravenous equivalents systemic acetaminophen also reduced postoperative nausea and vomiting compared with control, odds ratio (95% CI) of 0.25 (0.13 to 0.47), numbers needed to treat (95% CI)=3.3 (2.3 to 5.9).

DISCUSSION

Systemic acetaminophen, when used as a single-dose preventive regimen, is an effective intervention to reduce postoperative pain. It also reduces postoperative nausea and/or vomiting. Doses >1 g were not associated with greater reduction in pain outcomes.