Drug absorption from the small intestine in immediate postoperative patients

Influence of general anaesthesia on the intravenous acetaminophen pharmacokinetics in Beagle dogs

OBJECTIVE

To determine if general anaesthesia influences the intravenous (IV) pharmacokinetics (PK) of acetaminophen in dogs.

STUDY DESIGN

Prospective, crossover, randomized experimental study.

ANIMALS

A group of nine healthy Beagle dogs.

METHODS

Acetaminophen PK were determined in conscious and anaesthetized dogs on two separate occasions. Blood samples were collected before, and at 5, 10, 15, 30, 45, 60 and 90 minutes and 2, 3, 4, 6, 8, 12 and 24 hours after 20 mg kg^-1 IV acetaminophen administration. Haematocrit, total proteins, albumin, alanine aminotransferase, aspartate aminotransferase, urea and creatinine were determined at baseline and 24 hours after acetaminophen. The anaesthetized group underwent general anaesthesia (90 minutes) for dental cleaning. After the administration of dexmedetomidine (3 μg kg^-1) intramuscularly, anaesthesia was induced with propofol (2-3 mg kg^-1) IV, followed by acetaminophen administration. Anaesthesia was maintained with isoflurane in 50% oxygen (Fe'Iso 1.3-1.5%). Dogs were mechanically ventilated. Plasma concentrations were analysed with high-performance liquid chromatography. PK analysis was undertaken using compartmental modelling. A Wilcoxon test was used to compare PK data between groups, and clinical laboratory values between groups, and before versus 24 hours after acetaminophen administration. Data are presented as median and range (p < 0.05).

RESULTS

A two-compartmental model best described time-concentration profiles of acetaminophen. No significant differences were found for volume of distribution values 1.41 (0.94-3.65) and 1.72 (0.89-2.60) L kg^-1, clearance values 1.52 (0.71-2.30) and 1.60 (0.91-1.78) L kg^-1 hour^-1 or terminal elimination half-life values 2.45 (1.45-8.71) and 3.57 (1.96-6.35) hours between conscious and anaesthetized dogs, respectively. Clinical laboratory variables were within normal range. No adverse effects were recorded.

CONCLUSIONS AND CLINICAL RELEVANCE

IV acetaminophen PK in healthy Beagle dogs were unaffected by general anaesthesia under the study conditions. Further studies are necessary to evaluate the PK in different clinical contexts.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Absorption of ibuprofen orodispersible tablets in early postoperative phase - a pharmacokinetic study

OBJECTIVE

Patient-controlled oral analgesia has gained popularity in postoperative pain management. Anesthesia and surgery delay gastrointestinal tract function and this may therefore decrease bioavailability of drugs taken by mouth. To hasten absorption, an orodispersible ibuprofen tablet has been developed. In this study, we evaluated the pharmacokinetics and feasibility of orodispersible ibuprofen tablets in spine surgery patients.

METHODS

The study design was a prospective clinical trial where each patient served as her/his own control. Fifteen patients aged 19-75 years were given two orodispersible ibuprofen 200 mg tablets the day before surgery and two more tablets immediately after surgery. Blood samples for ibuprofen concentrations were taken at intervals for 6 hours following pre- and postsurgical administration of ibuprofen.

RESULTS

The mean preoperative area under time-concentration curve for ibuprofen (AUC_0-360) was 4806 (SD 1104) min·mg/L, and after surgery it was 2141 (583) min·mg/L (mean difference 2664, 95% CI for difference 2003 to 3325, p < .001). The mean of the maximum preoperative plasma concentration of ibuprofen was three times higher, 26.7 (7.7) mg/L, than the postoperative value of 8.6 (2.1) mg/L (mean diff. 18.1, 95% CI 13.9 to 22.4, p < .001). Times to maximum concentration were similar pre- and postoperatively at 155 (58) minutes and 169 (113) minutes (p = .67). No serious or unexpected adverse events were recorded.

CONCLUSIONS

While orodispersible ibuprofen tablets were feasible, ibuprofen absorption decreased immediately after surgery compared to the day before surgery. Thus, further studies are needed to establish the adequate initial postoperative dose.

Sufentanil sublingual formulation for the treatment of acute, moderate to severe postoperative pain in adult patients

INTRODUCTION

Sufentanil is a highly selective µ-opioid agonist commonly used by intravenous and intrathecal routes for acute pain. Sublingual sufentanil formulation for patient controlled analgesia (PCA) uses an innovative administration device that suspends a 15 µg nanotablet with a fixed lockout interval. The system is a non-invasive, less burdensome method of opioid delivery compared to intravenous and intrathecal routes. Sublingual nanotablet PCA transmucosal bioavailability is 59% and the meaningful analgesic onset time is 60 minutes. Areas covered: This paper focuses on the effectiveness, safety and feasibility of sufentanil PCA sublingual formulation for the management of postoperative pain. The paper is based on PubMed searches and the European Medicine Agency assessment report. Expert commentary: Under-treatment of acute pain is a substantial clinical problem. The initial experiences with the sublingual delivery system are encouraging. Sufentanil sublingual nanotablets intended for PCA device use are approved in Europe, and approval is pending in the United States.

Laparoscopic surgery: a narrative review of pharmacotherapy in pain management

Laparoscopic surgery is widespread, and an increasing number of surgeries are performed laparoscopically. Early pain after laparoscopy can be similar or even more severe than that after open surgery. Thus, proactive pain management should be provided. Pain after laparoscopic surgery is derived from multiple origins; therefore, a single agent is seldom sufficient. Pain is most effectively controlled by a multimodal, preventive analgesia approach, such as combining opioids with non-opioid analgesics and local anaesthetics. Wound and port site local anaesthetic injections decrease abdominal wall pain by 1-1.5 units on a 0-10 pain scale. Inflammatory pain and shoulder pain can be controlled by NSAIDs or corticosteroids. In some patient groups, adjuvant drugs, ketamine and α2-adrenergic agonists can be helpful, but evidence on gabapentinoids is conflicting. In the present review, the types of pain that need to be taken into account while planning pain management protocols and the wide range of analgesic options that have been assessed in laparoscopic surgery are critically assessed. Recommendations to the clinician will be made regarding how to manage acute pain and how to prevent persistent postoperative pain. It is important to identify patients at the highest risk for severe and prolonged post-operative pain, and to have a proactive strategy in place for these individuals.

Postoperative pain management in children and infants: an update

Many factors contribute to suboptimal pain management in children. Current evidence suggests that severe pain in children has significant long-lasting effects, even more so than in adults. In particular, recent evidence suggests a lack of optimal postoperative pain management in children, especially following ambulatory surgery. This review provides simple guidelines for the management of postoperative pain in children. It discusses the long-term effects of severe pain and how to evaluate pain in both healthy and neurologically impaired children, including neonates. Currently available treatment options are discussed with reference to the efficacy and side effects of opioid and non-opioid and regional analgesic techniques. The impact of preoperative anxiety on postoperative pain, and the efficacy of some nonpharmacological techniques such as hypnosis or distraction, are also discussed. Finally, basic organizational strategies are described, aiming to promote safer and more efficient postoperative pain management in children.

Postoperative plasma paracetamol levels following oral or intravenous paracetamol administration: a double-blind randomised controlled trial

In day-case surgery paracetamol is commonly given orally preoperatively, or intravenously intraoperatively. In this double-blind randomised controlled trial we investigated which of these methods of administration achieved therapeutic plasma levels most effectively in the early postoperative period. Thirty patients undergoing day case arthroscopy of the knee were randomised to receive either 1.0 g oral paracetamol 30 to 60 minutes preoperatively (20 patients) or 1.0 g intravenous paracetamol intraoperatively (10 patients). Plasma paracetamol levels were measured 30 minutes after arrival in the recovery room. Secondary outcomes included postoperative pain scores, rescue analgesia requirements and duration of stay in the recovery room. All patients receiving the intravenous preparation had plasma levels above the analgesic level compared to less than half (7/20) in the oral group. Mean plasma paracetamol levels were 88.6 µmol/l for the intravenous group and 53.2 µmol/l for the oral group (P=0.0005). There were trends towards reduced rescue analgesia and duration of stay in the recovery room for the intravenous group although not reaching statistical significance. There was no difference in pain scores between groups. Intraoperative administration of 1.0 g of intravenous paracetamol more reliably achieved effective paracetamol levels in the early postoperative period compared to an equal dose given orally preoperatively. Only a minority of patients receiving the 1.0 g oral dose preoperatively had plasma levels in the therapeutic analgesic range.

Combinatorial effect of non-steroidal anti-inflammatory drugs and NF-κB inhibitors in ovarian cancer therapy

Several epidemiological studies have correlated the use of non-steroidal anti-inflammatory drugs (NSAID) with reduced risk of ovarian cancer, the most lethal gynecological cancer, diagnosed usually in late stages of the disease. We have previously established that the pro-apoptotic cytokine melanoma differentiation associated gene-7/Interleukin-24 (mda-7/IL-24) is a crucial mediator of NSAID-induced apoptosis in prostate, breast, renal and stomach cancer cells. In this report we evaluated various structurally different NSAIDs for their efficacies to induce apoptosis and mda-7/IL-24 expression in ovarian cancer cells. While several NSAIDs induced apoptosis, Sulindac Sulfide and Diclofenac most potently induced apoptosis and reduced tumor growth. A combination of these agents results in a synergistic effect. Furthermore, mda-7/IL-24 induction by NSAIDs is essential for programmed cell death, since inhibition of mda-7/IL-24 by small interfering RNA abrogates apoptosis. mda-7/IL-24 activation leads to upregulation of growth arrest and DNA damage inducible (GADD) 45 α and γ and JNK activation. The NF-κB family of transcription factors has been implicated in ovarian cancer development. We previously established NF-κB/IκB signaling as an essential step for cell survival in cancer cells and hypothesized that targeting NF-κB could potentiate NSAID-mediated apoptosis induction in ovarian cancer cells. Indeed, combining NSAID treatment with NF-κB inhibitors led to enhanced apoptosis induction. Our results indicate that inhibition of NF-κB in combination with activation of mda-7/IL-24 expression may lead to a new combinatorial therapy for ovarian cancer.

Competitive inhibition of organic anion transporting polypeptide 1c1-mediated thyroxine transport by the fenamate class of nonsteroidal antiinflammatory drugs

Organic anion transporting polypeptide (Oatp) 1c1 is a high-affinity T(4) transporter with narrow substrate specificity expressed at the blood-brain barrier. A transport model using cells overexpressing Oatp1c1 was created to identify novel Oatp1c1 substrates and inhibitors. Rat Oatp1c1 was cloned and stably expressed in human embryonic kidney 293 cells. Oatp1c1-transfected human embryonic kidney 293 cells transported (125)I-labeled T(4) in a time-dependent manner that was completely abolished in the presence of excess unlabeled T(4). Next, various compounds, including inhibitors of thyroid hormone uptake, were screened for inhibitory effects on Oatp1c1-mediated T(4) uptake. Phenytoin (64%), indocyanine green (17%), fenamic acid (68%), diclofenac (51%), and meclofenamic acid (33%) all reduced T(4) uptake by Oatp1c1 when assayed at concentrations of 10 microM. Dose-response assays for the fenamic acids, iopanoic acid, indocyanine green, and phenytoin revealed IC(50) values for Oatp1c1 T(4) uptake below or near the blood plasma levels after therapeutic doses. Further kinetic assays and reciprocal plot analyses demonstrated that the fenamic acid diclofenac inhibited in a competitive manner. Finally, microvessels were isolated from adult rat brain and assessed for T(4) uptake. Ten micromolar of fenamate concentrations inhibited T(4) microvessel uptake with a similar hierarchical inhibition profile [fenamic acid (43%), diclofenac (78%), and meclofenamic acid (85%)], as observed for Oatp1c1 transfected cells. Oatp1c1 is expressed luminally and abluminally in the blood-brain barrier endothelial cell, and exhibits bidirectional transport capabilities. Together, these data suggest that Oatp1c1 transports fenamates into, and perhaps across, brain barrier cells.

Acetaminophen Overdose with Altered Acetaminophen Pharmacokinetics and Hepatotoxicity Associated with Premature Cessation of Intravenous N-Acetylcysteine Therapy

Objective

To report a case of erratic absorption, double peak serum concentrations, and hepatotoxicity following premature cessation of intravenous N-acetylcysteine (NAC) treatment in the setting of a massive acetaminophen overdose.

Case Summary:

A 78-year-old man reportedly ingested approximately 96 immediate-release acetaminophen 500-mg tablets (48 g) over a one-hour period in an apparent suicide attempt. The acetaminophen concentration at 2.25 hours was 264 μg/mL. Intravenous NAC was initiated 5 hours postingestion. At 6.25 hours postingestion, the acetaminophen concentration was 281 μg/mL. Following administration of intravenous NAC for 21 hours, therapy was discontinued despite a residual acetaminophen concentration of 116 μg/mL. The patient experienced hepatotoxicity, coagulopathy, and renal injury. Pharmacokinetic analysis revealed significantly prolonged acetaminophen absorption and a second peak acetaminophen concentration of 228 μg/mL approximately 48 hours post ingestion. Direct in-hospital monitoring of the patient made a second ingestion unlikely.

Discussion:

Acetaminophen overdose is usually effectively managed with NAC. Patients with massive ingestions may have altered absorption kinetics due to acetaminophen's solubility being exceeded, physiologically or chemically altered gastrointestinal emptying or motility, or other factors. These patients may benefit from gastrointestinal decontamination and prolonged NAC therapy.

Conclusions:

In patients with massive acetaminophen ingestion, erratic absorption may occur, and toxic serum concentrations may persist beyond a standard 21–hour course of intravenous NAC therapy. Acetaminophen concentrations and aminotransferase levels should be evaluated at the completion of the intravenous NAC infusion to ensure complete elimination of acetaminophen and absence of hepatotoxicity and to exclude the need lor prolonged treatment.

Does coronary artery bypass surgery affect metoprolol bioavailability

BACKGROUND

beta-blockers are commonly administered in patients with coronary artery bypass surgery (CABG). Despite this therapy, however, the incidence of postoperative atrial fibrillation (AF) is high (9-19%), and it is unknown why the beta-blockers do not reduce the incidence of AF more efficiently. In this pharmacokinetics study, in which the patients acted as their own controls, we have evaluated the bioavailability of perioperative metoprolol tablets in CABG surgery patients.

METHODS

Twelve male patients, aged 45-64 years, scheduled for CABG surgery were administered an initial 50 mg metoprolol tartrate tablet orally on the morning of the preoperative day and thereafter at 12-h intervals. Regular blood samples were collected up to 12 h after the first administration of the drug on the preoperative day as well on the first and third postoperative days. The plasma concentration for metoprolol was analyzed (limit of quantification = 0.001 mg/L) using liquid chromatography-tandem mass spectrometry.

RESULTS

The bioavailability of the metoprolol was significantly less on the first postoperative day, with AUC(0-12) values ranging from 0.7 to 17.1 (median: 7.2) mg min/L, than on the preoperative day, with AUC(0-12) values of 5.1-26.7 (12.6) mg min/L; however, it returned to the preoperative values on the third postoperative day, with AUC(0-12) values of 3.5-25.2 (15.2) mg min/L. Similar changes were observed in C(max) values: preoperative C(max) ranged between 0.026 and 0.123 (0.060) mg/L, on the first postoperative day, the C(max) ranged between 0.003 and 0.093 (0.025) mg/L, and on the third postoperative day, the C(max) ranged between 0.009 and 0.136 (0.061) mg/L. There was no correlation between the pharmacokinetic parameters and patient characteristics, but both the preoperative C(max) and C(60) correlated significantly with the postoperative C(max) (Pearson correlation coefficient: 0.61-0.72). One patient with one of the lowest rates and extent of metoprolol absorption developed AF.

CONCLUSION

This study indicates that the bioavailability of metoprolol is markedly reduced when administered in tablet form during the early phase after CABG.

A novel pathway involving melanoma differentiation associated gene-7/interleukin-24 mediates nonsteroidal anti-inflammatory drug-induced apoptosis and growth arrest of cancer cells

Numerous studies show that nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in chemoprevention or treatment of cancer. Nevertheless, the mechanisms underlying these antineoplastic effects remain poorly understood. Here, we report that induction of the cancer-specific proapoptotic cytokine melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24) by several NSAIDs is an essential step for induction of apoptosis and G(2)-M growth arrest in cancer cells in vitro and inhibition of tumor growth in vivo. We also show that MDA-7/IL-24-dependent up-regulation of growth arrest and DNA damage inducible 45 alpha (GADD45alpha) and GADD45gamma gene expression is sufficient for cancer cell apoptosis via c-Jun NH(2)-terminal kinase (JNK) activation and growth arrest induction through inhibition of Cdc2-cyclin B checkpoint kinase. Knockdown of GADD45alpha and GADD45gamma transcription by small interfering RNA abrogates apoptosis and growth arrest induction by the NSAID treatment, blocks JNK activation, and restores Cdc2-cyclin B kinase activity. Our results establish MDA-7/IL-24 and GADD45alpha and GADD45gamma as critical mediators of apoptosis and growth arrest in response to NSAIDs in cancer cells.

The effect of anesthetic technique on early postoperative gastric emptying: comparison of propofol-remifentanil and opioid-free sevoflurane anesthesia

PURPOSE

A postoperative decrease in the gastric emptying (GE) rate may delay the early start of oral feeding and alter the bioavailability of orally administered drugs. The aim of this study was to compare the effect on early gastric emptying between two anesthetic techniques.

METHODS

Fifty patients (age, 19-69 years) undergoing day-case laparoscopic cholecystectomy were randomly assigned to received either total intravenous anesthesia with propofol/remifentanil/rocuronium (TIVA; n = 25) or inhalational opioid-free anesthesia with sevoflurane/rocuronium (mask induction; GAS; n = 25). Postoperative gastric emptying was evaluated by the acetaminophen method. After arrival in the recovery unit, acetaminophen (paracetamol) 1.5 g was given through a nasogastric tube, and blood samples were drawn during a 2-h period. The area under the serum-acetaminophen concentration curve from 0-60 min (AUC60), the maximal concentration (Cmax), and the time to reach C-max (Tmax) were calculated.

RESULTS

Twelve patients were excluded due to surgical complications (e.g., conversion to open surgery) and difficulty in drawing blood samples (TIVA, n = 7; GAS, n = 5). Gastric emptying parameters were (mean +/- SD): TIVA, AUC60, 2458 +/- 2775 min.micromol.l(-1); Cmax, 71 +/- 61 micromol.l(-1); and Tmax, 81 +/- 37 min; and GAS, AUC60, 2059 +/- 2633 min.micromol.l(-1); Cmax, 53 +/- 53 micromol.l(-1); and Tmax, 83 +/- 41 min. There were no significant differences between groups.

CONCLUSION

There was no major difference in early postoperative gastric emptying between inhalation anesthesia with sevoflurane versus total intravenous anesthesia with propofol-remifentanil. Both groups showed a pattern of delayed gastric emptying, and the variability in gastric emptying was high. Perioperative factors other than anesthetic technique may have more influence on gastric emptying.