Fospropofol

Developing a PK-PD model for propofol in exhaled air and the BIS following fospropofol disodium in beagles

BACKGROUND

Fospropofol, a water-soluble prodrug of propofol, is metabolized into propofol by alkaline phosphatase after administration. This study aimed to develop a pharmacokinetic-pharmacodynamic (PK-PD) model that correlates the propofol concentration in exhaled air (Ce-pro-f) with its anesthetic effects, as measured by the bispectral index (BIS) in beagles.

METHODS

Beagles receiving a single intravenous infusion of fospropofol at varying doses were divided into three groups (n = 6): the DBL-fospro group (15 mg/kg), the DBM-fospro group (30 mg/kg), and the DBH-fospro group (60 mg/kg). Propofol levels were monitored using VUV-TOF MS from pre-administration to recovery. Correlations between Ce-pro-f and blood concentration (Cblood-pro), as well as between Ce-pro-f and the BIS were investigated. PK, PD, and PK-PD models describing the relationship between Ce and BIS were also analyzed.

RESULTS

Propofol concentration in exhaled air can be quantified using VUV-TOF MS at a mass-to-charge ratio of 177.6. After fospropofol injection, the peak Ce-pro-f was delayed compared to Cblood-pro. The PK model of Ce-pro-f can be described using a noncompartmental approach, corresponding to the linear PK characteristics. Additionally, Ce-pro-f showed a moderate to strong negative correlation with BIS values. In the PK-PD model, the PK component was well characterized by a two-compartment model incorporating a first-order delay to account for the time lag of Ce-pro-f relative to Cblood-pro. The PD component was well fitted by the inhibitory sigmoid Emax model, with an indirect connection model selected to explain the observed lag between BIS signals and Ce-pro-f peaks.

CONCLUSIONS

This study is the first to develop a PK-PD model for exhaled propofol in beagles after fospropofol disodium administration. The PK profile was described by a two-compartment model with a first-order delay, and the PD profile was modeled using an inhibitory sigmoid Emax model with an indirect connection model to capture the lag between BIS and exhaled propofol peaks.

Prodrug Strategy to Address Impaired Oral Absorption of a Weakly Basic TYK2 Inhibitor Caused by a Gastric Acid-Reducing Agent

The pH-dependent solubility of the weakly basic TYK2 inhibitor 1 posed a risk to its advancement, given that drugs with such profiles have exhibited drug-drug interaction (DDI) with stomach acid-reducing agents in humans. In a rat model of pH dependence, preadministration of famotidine caused a 2.4-fold lower exposure of 1 when compared to control rats, implying that pH-dependent oral absorption can reduce the active drug's exposure and translate to subtherapeutic treatment. As part of risk mitigation, a prodrug strategy was explored by synthesizing solubility-enhancing prodrugs, resulting in the identification of lead prodrug 3c with acceptable stability and solubility profiles. In rats, the prodrug eliminated the significant difference in AUC and Cmax between pentagastrin and famotidine arms, thereby effectively mitigating the impaired drug absorption at the elevated pH relevant for absorption and DDI with famotidine. The prodrug also facilitated dose-proportional systemic exposure of 1 following dose escalation in rats and monkeys.

Efficacy and safety of fospropofol disodium sedation for same-day bidirectional endoscopy in elderly patients: protocol for a prospective, single-center, randomized, double-blind, non-inferiority trial

Introduction

Fospropofol disodium is a novel prodrug that has improved pharmacokinetic and pharmacodynamic properties when compared with propofol. This trial aims to compare the efficacy and safety of fospropofol versus propofol sedation for same-day bidirectional endoscopy in elderly patients.

Methods and analysis

This is a prospective, single-center, double-blind, randomized, propofol-controlled, non-inferiority trial. A total of 256 patients aged 65 years or older, who are scheduled for same-day bidirectional endoscopy under sedation, will be randomly allocated, in a 1:1 ratio, to either fospropofol group or propofol group (n = 128 in each group). All patients will receive analgesic pre-treatment with sufentanil 5 μg. Two minutes later, an initial bolus dose of fospropofol 6.5 mg/kg or 1.5 mg/kg propofol and supplemental doses of fospropofol 1.6 mg/kg or 0.5 mg/kg propofol will be titrated as needed to achieve target sedation levels during the procedures. The primary outcome is the success rate of same-day bidirectional endoscopy. Secondary outcomes include the time to successful induction of sedation, duration, time to being fully alert, time to patient discharge, endoscopist satisfaction, patient satisfaction, and the top-up frequency and dosage of sedative medications. The safety endpoints consist of adverse events concerning cough reflex, gag reflexes, body movement, muscular tremor, and pain on injection. Sedation-related AEs, including episodes of desaturation, severe desaturation (SpO2 < 90%), hypotension, severe hypotension (decrease in MBP ≥30% of baseline), and bradycardia, will also be recorded. Data will be analyzed on an intention-to-treat basis.

Discussion

We hypothesize that the efficacy and safety of fospropofol sedation for elderly patients undergoing same-visit bidirectional endoscopy will not be inferior to that of propofol. Our findings will potentially provide a new sedation regimen for same-visit bidirectional endoscopy in elderly patients.

Clinical Trial Registration

clinicaltrials.gov, identifier NCT02875639.

Advances in Analgosedation and Periprocedural Care for Gastrointestinal Endoscopy

The number and complexity of endoscopic gastrointestinal diagnostic and therapeutic procedures is globally increasing. Procedural analgosedation during gastrointestinal endoscopic procedures has become the gold standard of gastrointestinal endoscopies. Patient satisfaction and safety are important for the quality of the technique. Currently there are no uniform sedation guidelines and protocols for specific gastrointestinal endoscopic procedures, and there are several challenges surrounding the choice of an appropriate analgosedation technique. These include categories of patients, choice of drug, appropriate monitoring, and medical staff providing the service. The ideal analgosedation technique should enable the satisfaction of the patient, their maximum safety and, at the same time, cost-effectiveness. Although propofol is the gold standard and the most used general anesthetic for endoscopies, its use is not without risks such as pain at the injection site, respiratory depression, and hypotension. New studies are looking for alternatives to propofol, and drugs like remimazolam and ciprofol are in the focus of researchers' interest. New monitoring techniques are also associated with them. The optimal technique of analgosedation should provide good analgesia and sedation, fast recovery, comfort for the endoscopist, patients' safety, and will have financial benefits. The future will show whether these new drugs have succeeded in these goals.

Structural Modification in Anesthetic Drug Development for Prodrugs and Soft Drugs

Among the advancements in drug structural modifications, the increased focus on drug metabolic and pharmacokinetic properties in the anesthetic drug design process has led to significant developments. Drug metabolism also plays a key role in optimizing the pharmacokinetics, pharmacodynamics, and safety of drug molecules. Thus, in the field of anesthesiology, the applications of pharmacokinetic strategies are discussed in the context of sedatives, analgesics, and muscle relaxants. In this review, we summarize two approaches for structural optimization to develop anesthetic drugs, by designing prodrugs and soft drugs. Drugs that both failed and succeeded during the developmental stage are highlighted to illustrate how drug metabolism and pharmacokinetic optimization strategies may help improve their physical and chemical properties.

What's New in Intravenous Anaesthesia? New Hypnotics, New Models and New Applications

New anaesthetic drugs and new methods to administer anaesthetic drugs are continually becoming available, and the development of new PK-PD models furthers the possibilities of using arget controlled infusion (TCI) for anaesthesia. Additionally, new applications of existing anaesthetic drugs are being investigated. This review describes the current situation of anaesthetic drug development and methods of administration, and what can be expected in the near future.

Safety and efficacy of remimazolam in high risk colonoscopy: A randomized trial

BACKGROUND

Procedural sedation of ASA III/IV patients has increased risk. Remimazolam (an ultra-short-acting benzodiazepine) has proven safe and efficient for outpatient colonoscopy sedation.

METHODS

A double-blind, randomized, multi-center, parallel group trial was performed, comparing remimazolam to placebo with an additional open-label arm for midazolam in procedural sedation of 79 ASA III/IV patients undergoing colonoscopy. This was the third of 3 Phase III trials for remimazolam in the procedural sedation program. The primary end point was the safety of remimazolam.

RESULTS

Of 79 patients randomized at 3 US sites, 77 underwent sedation and colonoscopy (31 received remimazolam, 16 placebo and 30 midazolam). Incidence and frequency of treatment emergent adverse events (TEAEs) were comparable in all three treatment arms, and independent of ASA status. One TEAE leading to discontinuation and one serious TEAE were reported; both in the open label midazolam arm. The efficacy endpoint was achieved for remimazolam, placebo, and midazolam in 87.1%, 0%, and 13.3% of patients (p<0.00001 for remimazolam versus placebo and versus midazolam, respectively).

CONCLUSIONS

Remimazolam is safe and efficient in procedural sedation of high risk ASA patients undergoing colonoscopy, showing a safety profile comparable to that in low risk ASA.

Phosphine Oxides from a Medicinal Chemist's Perspective: Physicochemical and in Vitro Parameters Relevant for Drug Discovery

Phosphine oxides and related phosphorus-containing functional groups such as phosphonates and phosphinates are established structural motifs that are still underrepresented in today's drug discovery projects, and only few examples can be found among approved drugs. In this account, the physicochemical and in vitro properties of phosphine oxides and related phosphorus-containing functional groups are reported and compared to more commonly used structural motifs in drug discovery. Furthermore, the impact on the physicochemical properties of a real drug scaffold is exemplified by a series of phosphorus-containing analogs of imatinib. We demonstrate that phosphine oxides are highly polar functional groups leading to high solubility and metabolic stability but occasionally at the cost of reduced permeability. We conclude that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist's toolbox.

The preclinical pharmacological study on HX0969W, a novel water-soluble pro-drug of propofol, in rats

Background

Propofol is the most widely used intravenous sedative-hypnotic anesthetic in clinical practice. However, many serious side effects have been related to its lipid emulsion formulation. The pro-drug design approach was used to develop the water-soluble propofol, which could effectively resolve the limitations associated with the lipid emulsion formulation. Thus, the new water-soluble pro-drug of propofol, HX0969W, was designed and synthesized. The objective of this study was to conduct preclinical pharmacological studies on this novel water-soluble pro-drug of propofol.

Methods

The assessment of the loss of the righting reflex (LoRR) was used for the pharmacodynamic study, and liquid chromatography-tandem mass spectrometry and high-performance liquid chromatography- fluorescence were used for the pharmacokinetic study.

Results

The potency of HX0969W (ED₅₀ [95% CI], 46.49 [43.89–49.29] mg/kg) was similar to that of fospropofol disodium (43.66 [43.57–43.75] mg/kg), but was lower than that of propofol (4.82 [4.8–14.82] mg/kg). Administered with a dose of 2-fold ED₅₀, propofol required a shorter time to cause LoRR than that of HX0969W and fospropofol. However, the LoRR duration was significantly longer in response to the administration of HX0969W and fospropofol disodium than that caused by propofol. In the pharmacokinetic study, the C_max of fospropofol was higher than that of HX0969W. HX0969W had a shorter mean residual time and a rapid clearance rate than that of fospropofol disodium. There was no significant difference between the T_max of the propofol whether it was released by HX0969W or fospropofol disodium; the C_max of propofol released by HX0969W was similar to that of propofol, which was higher than the propofol released by fospropofol disodium.

Metabolic Profiles of Propofol and Fospropofol: Clinical and Forensic Interpretative Aspects

Propofol is an intravenous short-acting anesthetic widely used to induce and maintain general anesthesia and to provide procedural sedation. The potential for propofol dependency and abuse has been recognized, and several cases of accidental overdose and suicide have emerged, mostly among the health professionals. Different studies have demonstrated an unpredictable interindividual variability of propofol pharmacokinetics and pharmacodynamics with forensic and clinical adverse relevant outcomes (e.g., pronounced respiratory and cardiac depression), namely, due to polymorphisms in the UDP-glucuronosyltransferase and cytochrome P450 isoforms and drugs administered concurrently. In this work the pharmacokinetics of propofol and fospropofol with particular focus on metabolic pathways is fully reviewed. It is concluded that knowing the metabolism of propofol may lead to the development of new clues to help further toxicological and clinical interpretations and to reduce serious adverse reactions such as respiratory failure, metabolic acidosis, rhabdomyolysis, cardiac bradyarrhythmias, hypotension and myocardial failure, anaphylaxis, hypertriglyceridemia, renal failure, hepatomegaly, hepatic steatosis, acute pancreatitis, abuse, and death. Particularly, further studies aiming to characterize polymorphic enzymes involved in the metabolic pathway, the development of additional routine forensic toxicological analysis, and the relatively new field of ‘‘omics” technology, namely, metabolomics, can offer more in explaining the unpredictable interindividual variability.

Recent advances in intravenous anesthesia and anesthetics

Anesthesiology, as a field, has made promising advances in the discovery of novel, safe, effective, and efficient methods to deliver care. This review explores refinement in the technology of soft drug development, unique anesthetic delivery systems, and recent drug and device failures.

Dexmedetomidine plus sufentanil for pediatric flexible bronchoscopy: A retrospective clinical trial

Several studies have reported the use of dexmedetomidine (DEX) plus opioids for flexible bronchoscopy in both adults and children. To determine whether DEX plus sufentanil (SF) is safe for children, 142 children undergoing flexible bronchoscopy were assigned to one of three groups, each of which received the same SF loading dose and similar DEX and SF maintenance doses, but different loading doses of DEX: DS1 (DEX 0.5 μg·kg^–1), DS2 (DEX 1.0 μg·kg^–1), and DS3 (DEX 1.5 μg·kg^–1). The Ramsay sedation scale was maintained at 3 in all groups. Results showed that anesthesia onset time was shorter, and the perioperative hemodynamic profile was more stable, in the DS3 group. The number of intraoperative movements was also lowest in the DS3 group. The time to first dose of rescue midazolam and lidocaine was significantly longer, but the total corresponding accumulated doses were lower in the DS3 group. Although the time to recovery prior to discharge from the post anesthesia care unit was longer, the overall incidence of tachycardia was lower in the DS3 group, and it received the highest bronchoscopist satisfaction score among the three groups. We therefore conclude that high-dose DEX plus SF can be safely and efficaciously used in children undergoing flexible bronchoscopy.

Pharmacologic Considerations for Pediatric Sedation and Anesthesia Outside the Operating Room: A Review for Anesthesia and Non-Anesthesia Providers

Understanding the pharmacologic options for pediatric sedation outside the operating room will allow practitioners to formulate an ideal anesthetic plan, allaying anxiety and achieving optimal immobilization while ensuring rapid and efficient recovery. The authors identified relevant medical literature by searching PubMed, MEDLINE, Embase, Scopus, Web of Science, and Google Scholar databases for English language publications covering a period from 1984 to 2017. Search terms included pediatric anesthesia, pediatric sedation, non-operating room sedation, sedation safety, and pharmacology. As a narrative review of common sedation/anesthesia options, the authors elected to focus on studies, reviews, and case reports that show clinical relevance to modern day sedation/anesthesia practice. A variety of pharmacologic agents are available for sedation/anesthesia in pediatrics, including midazolam, fentanyl, ketamine, dexmedetomidine, etomidate, and propofol. Dosing ranges reported are a combination of what is discussed in the reviewed literature and text books along with personal recommendations based on our own practice. Several reports reveal that ketofol (a combination of ketamine and propofol) is quite popular for short, painful procedures. Fospropofol is a newer-generation propofol that may confer advantages over regular propofol. Remimazolam combines the pharmacologic effects of remifentanil and midazolam. A variety of etomidate derivatives such as methoxycarbonyl-etomidate, carboetomidate, methoxycarbonyl-carboetomidate, and cyclopropyl-methoxycarbonyl metomidate are in development stages. The use of nitrous oxide as a mild sedative, analgesic, and amnestic agent is gaining popularity, especially in the ambulatory setting. Utilizing a dedicated and experienced team to provide sedation enhances safety. Furthermore, limiting sedation plans to single-agent pharmacy appears to be safer than using multi-agent plans.

The safety and efficacy of dexmedetomidine-remifentanil in children undergoing flexible bronchoscopy: A retrospective dose-finding trial

Flexible bronchoscopy is more and more used for diagnosis and management of various pulmonary diseases in pediatrics. As poor coordination of children, the procedure is usually performed under general anesthesia with spontaneous or controlled ventilation to increase children and bronchoscopists' safety and comfort. Previous studies have reported that dexmedetomidine (DEX) could be safely and effectively used for flexible bronchoscopy in both adulate and children. However, there is no trial to evaluate the dose-finding of safety and efficacy of dexmedetomidine-remifentanil (DEX-RF) in children undergoing flexible bronchoscopy.The objective of this study is to evaluate the dose-finding of safety and efficacy of DEX-RF in children undergoing flexible bronchoscopy.One hundred thirty-five children undergoing flexible bronchoscopy with DEX-RF were divided into 3 groups: Group DR1 (n = 47, DEX infusion at 0.5 μg·kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; RF infusion at 0.5 μg kg for 2 minutes, then adjusted to 0.05-0.2 μg kg min), Group DR2 (n = 43, DEX infusion at 1 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; RF infusion at 1 μg kg for 2 minutes, then adjusted to 0.05-0.2 μg kg min), Group DR3 (n = 45, DEX infusion at 1.5 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; RF infusion at 1 μg kg for 2 minutes, then adjusted to 0.05-0.2 μg kg min). Ramsay sedation scale of the 3 groups was maintained 3. Anesthesia onset time, total number of intraoperative children movements, hemodynamics (heart rate, arterial pressure, pulse oxygen saturation (SpO2), respiratory rate), total cumulative dose of dexmedetomidine and remifentanil, the amount of midazolam and lidocaine, time to first dose of rescue midazolam and lidocaine, postoperative recovery time, adverse events, bronchoscopist satisfaction score were recorded.Anesthesia onset time was significantly shorter in DR3 group (14.23 ± 5.45 vs 14.45 ± 5.12 vs 11.13 ± 4.51 minutes, respectively, of DR1, DR2, DR3, P = 0.003). Additionally, the perioperative hemodynamic profile was more stable in group DR3 than that in the other 2 groups. Total number of children movements during flexible bronchoscopy was higher in DR1 group than the other 2 groups (46.81% 22/47 vs 34.88% 15/43 vs 17.78% 8/45, respectively, of DR1, DR2, DR3, P = 0.012). Total doses of rescue midazolam and lidocaine were significantly higher in DR1 and DR2 groups than that of DR3 group (P = 0.000). The time to first dose of rescue midazolam and lidocaine was significantly longer in DR3 group than DR1 and DR2 groups (P = 0.000). Total cumulative dose of dexmedetomidine was more in DR2 and DR3 groups (P = 0.000), while the amount of remifentanil was more in DR1 and DR2 groups (P = 0.000). The time to recovery for discharge from the PACU was significantly shorter in DR1 group compared with the other 2 groups (P = 0.000). Results from bronchoscopist satisfaction score showed significantly higher in DR2 and DR3 groups than that of DR1 group (P = 0.025). There were significant differences among the 3 groups in terms of the overall incidence of hypertension, tachycardia, hypoxemia, and cough (P < 0.05).Though it required longer recovery time, high dose of DEX-RF, which provided better stable hemodynamic profiles and bronchoscopist satisfaction score, less amount of rescue scheme, and children movements, could be safely and efficacy used in children undergoing flexible bronchoscopy.

Gastrointestinal delivery of propofol from fospropofol: its bioavailability and activity in rodents and human volunteers

BACKGROUND

Propofol is a safe and widely used intravenous anesthetic agent, for which additional clinical uses including treatment of migraine, nausea, pain and anxiety have been proposed (Vasileiou et al. Eur J Pharmacol 605:1-8, 2009). However, propofol suffers from several disadvantages as a therapeutic outside anesthesia including its limited aqueous solubility and negligible oral bioavailability. The purpose of the studies described here was to evaluate, in both animals and human volunteers, whether fospropofol (a water soluble phosphate ester prodrug of propofol) would provide higher propofol bioavailability through non-intravenous routes.

METHODS

Fospropofol was administered via intravenous, oral and intraduodenal routes to rats. Pharmacokinetic and pharmacodynamic parameters were then evaluated. Based on the promising animal data we subsequently conducted an oral and intraduodenal pharmacokinetic/pharmacodynamic study in human volunteers.

RESULTS

In rats, bioavailability of propofol from fospropofol delivered orally was found to be appreciable, in the order of around 20-70%, depending on dose. Availability was especially marked following fospropofol administration via the intraduodenal route, where bioavailability approximated 100%. Fospropofol itself was not appreciably bioavailable when administered by any route except for intravenous. Pharmacologic effect following oral fospropofol was confirmed by observation of sedation and alleviation of thermal hyperalgesia in the rat chronic constrictive injury model of neuropathic pain. The human data also showed systemic availability of propofol from fospropofol administration via oral routes, a hereto novel finding. Assessment of sedation in human volunteers was correlated with pharmacokinetic measurements.

CONCLUSIONS

These data suggest potential utility of oral administration of fospropofol for various therapeutic indications previously considered for propofol.

Propofol alternatives in gastrointestinal endoscopy anesthesia

Although propofol has been the backbone for sedation in gastrointestinal endoscopy, both anesthesiologists and endoscopists are faced with situations where an alternative is needed. Recent national shortages forced many physicians to explore these options. A midazolam and fentanyl combination is the mainstay in this area. However, there are other options. The aim of this review is to explore these options. The future would be, invariably, to move away from propofol. The reason is not in any way related to the drawbacks of propofol as a sedative. The mandate that requires an anesthesia provider to administer propofol has been a setback in many countries. New sedative drugs like Remimazolam might fill this void in the future. In the meantime, it is important to keep an open eye to the existing alternatives.

The efficacy of intracoelomic fospropofol in red-eared sliders (Trachemys scripta elegans)

Intravenous anesthetic delivery in reptiles can be challenging. Current injectable techniques have varied induction/recovery times and anesthetic quality. This study hypothesized that intracoelomic administration of a new anesthetic, fospropofol, in turtles would result in dose-dependent anesthesia and respiratory depression. A two-part prospective trial using adult red-eared slider turtles (Trachemys scripta elegans) weighing 764 +/- 17 g was conducted to determine an effective anesthetic dose and to evaluate the anesthetic quality, duration, and respiratory effects of an efficacious dose. In part 1, six turtles were randomly administered 25-mg/ kg (low-dose [LD]) and 50-mg/kg (high-dose [HD]) fospropofol in a crossover design. Respiratory rate, immobility, and muscle relaxation scores were evaluated for 180 min. In part 2, eight turtles were administered HD fospropofol. Immobility and muscle relaxation (front and hind limb) scores and time to endotracheal intubation/extubation were evaluated until scores returned to baseline. In part 1, the LD group had significantly lower immobility and muscle relaxation scores versus the HD group over time (both P < 0.05); scores were significantly elevated from baseline for 20-120 min and 15-180 min, respectively (all P < 0.05). Although not significantly different between groups (P > 0.05), respiratory rate was significantly decreased from baseline from 10 to 120 min (all P < 0.05). In part 2, HD fospropofol decreased respiratory rate from 21.5 +/- 2.9 breaths/min to 0.1 +/- 0.1 breaths/min, similar to the results in part 1. Maximal reductions in mobility and front and hind limb motor tone occurred at 39.0 +/- 4.1, 30.8 +/- 3.6, and 24.0 +/- 3.6 min, respectively. Intubation in 7/8 turtles occurred at 45.7 +/- 5.4 min and extubation at 147.0 +/- 23.2 min. However, 2/8 turtles showed prolonged anesthetic effects, requiring resuscitative efforts for recovery. Due to the unpredictable quality and duration of anesthesia with intracoelomic fospropofol, it should be used with caution for general anesthesia in red-eared sliders at the doses and administration route investigated.

Efficacy comparison of the novel water-soluble propofol prodrug HX0969w and fospropofol in mice and rats

BACKGROUND

HX0969w is a novel water-soluble prodrug designed to release propofol and gamma-hydroxybutyrate (GHB) and has a sedative-hypnotic effect. This study was performed to compare the efficacy of HX0969w with fospropofol in mice and rats.

METHODS

We performed hydrolysis studies in the plasma from mice and rats. The half-maximal effective doses (ED50) and half-maximal lethal doses (LD50) of fospropofol and HX0969w were determined. A pharmacodynamics comparison of these two compounds was also performed. Time to loss of righting reflex, time to return of righting reflex, recovery time, and adverse effects were recorded.

RESULTS

The hydrolysis studies demonstrated that HX0969w released propofol as expected. HX0969w ED50 values in mice and rats were 133.03 and 53.79 mg kg(-1), respectively, and LD50 values were 607.11 and 283.79 mg kg(-1), respectively. The calculated therapeutic index (TI), safety index (SI), and certain safety factor (CSF) of HX0969w were 4.56, 3.33, and 2.92 for mice, and 5.28, 3.94, and 3.49 for rats, respectively. The pharmacodynamic comparison studies suggest that HX0969w has a longer onset time and shorter duration than fospropofol.

CONCLUSIONS

Similar to fospropofol, HX0969w is an effective, water-soluble prodrug that is capable of inducing a sedative-hypnotic effect in mice and rats. Unlike fospropofol, HX0969w releases GHB instead of formaldehyde. Further studies regarding the efficacy and safety of HX0969w are necessary.

Sedation in gastrointestinal endoscopy: current issues

Diagnostic and therapeutic endoscopy can successfully be performed by applying moderate (conscious) sedation. Moderate sedation, using midazolam and an opioid, is the standard method of sedation, although propofol is increasingly being used in many countries because the satisfaction of endoscopists with propofol sedation is greater compared with their satisfaction with conventional sedation. Moreover, the use of propofol is currently preferred for the endoscopic sedation of patients with advanced liver disease due to its short biologic half-life and, consequently, its low risk of inducing hepatic encephalopathy. In the future, propofol could become the preferred sedation agent, especially for routine colonoscopy. Midazolam is the benzodiazepine of choice because of its shorter duration of action and better pharmacokinetic profile compared with diazepam. Among opioids, pethidine and fentanyl are the most popular. A number of other substances have been tested in several clinical trials with promising results. Among them, newer opioids, such as remifentanil, enable a faster recovery. The controversy regarding the administration of sedation by an endoscopist or an experienced nurse, as well as the optimal staffing of endoscopy units, continues to be a matter of discussion. Safe sedation in special clinical circumstances, such as in the cases of obese, pregnant, and elderly individuals, as well as patients with chronic lung, renal or liver disease, requires modification of the dose of the drugs used for sedation. In the great majority of patients, sedation under the supervision of a properly trained endoscopist remains the standard practice worldwide. In this review, an overview of the current knowledge concerning sedation during digestive endoscopy will be provided based on the data in the current literature.

[Fospropofol: A new prodrug of propofol]

The development of new propofol formulations has advanced rapidly in the last ten years with the achievement of the marketing a new prodrug of propofol: fospropofol, pharmacologically different from the original compound. It is a water soluble compound that requires metabolism of the prodrug to propofol, which leads to a time delay between its administration and the appearance of its pharmacological effect. Its pharmacokinetic and pharmacodynamic characteristics are different to the original formula. Due to its formulation it does not cause pain on intravenous injection, does not lead to hyperlipidaemia or excess bacterial growth. Although it is currently unavailable in Spain, it has been approved by the FDA (American Food and Drug Administration) for sedation in controlled care in diagnostic and therapeutic procedures in adults. It must only be administered by personnel qualified to administer anaesthesia, and the patients must be monitored throughout the whole procedure.

Inhibitors of human immunodeficiency virus type 1 (HIV-1) attachment 6. Preclinical and human pharmacokinetic profiling of BMS-663749, a phosphonooxymethyl prodrug of the HIV-1 attachment inhibitor 2-(4-benzoyl-1-piperazinyl)-1-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)-2-oxoethanone (BMS-488043)

BMS-663749, a phosphonooxymethyl prodrug 4 of the HIV-1 attachment inhibitor 2-(4-benzoyl-1-piperazinyl)-1-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)-2-oxoethanone (BMS-488043) (2) was prepared and profiled in a variety of preclinical in vitro and in vivo models designed to assess its ability to deliver parent drug following oral administration. The data showed that prodrug 4 had excellent potential to significantly reduce dissolution rate-limited absorption following oral dosing in humans. Clinical studies in normal healthy subjects confirmed the potential of 4, revealing that the prodrug significantly increased both the AUC and C(max) of 2 compared to a solid capsule formulation containing the parent drug upon dose escalation. These data provided guidance for further efforts to obtain an effective HIV-1 attachment inhibitor.

Sedation and analgesia in the mechanically ventilated patient

Sedation and analgesia are important components of care for the mechanically ventilated patient in the intensive care unit (ICU). An understanding of commonly used medications is essential to formulate a sedation plan for individual patients. The specific physiological changes that a critically ill patient undergoes can have direct effects on the pharmacology of drugs, potentially leading to interpatient differences in response. Objective assessments of pain, sedation, and agitation have been validated for use in the ICU for assessment and titration of medications. An evidence-based strategy for administering these drugs can lead to improvements in short- and long-term outcomes for patients. In this article, we review advances in the field of ICU sedation to provide an up-to-date perspective on management of the mechanically ventilated ICU patient.

Determination of HX0969w in Rabbit Whole Blood by Liquid Chromatography—Tandem Mass Spectrometry and its Application in a Pharmacokinetic Study

HX0969w is a novel carboxylate ester prodrug of propofol. After intravenous administration of HX0969w, the compound is rapidly hydrolyzed to its active metabolite propofol. A liquid chromatography–tandem mass spectrometry method with electrospray ionization has been developed for determination of HX0969w in rabbit whole blood. Protein precipitation with methanol was used for sample preparation and 7-hydroxycoumarin served as internal standard. The standard curve ranged from 50.1 ng mL−1. to 15,030 ng mL−1. The lower limit of quantification for HX0969w was 50.1 ng mL−1. The intra- and inter-day accuracies were within ±10% and precisions were below 5.52%. The method was successfully applied to samples from a rabbit pharmacokinetic study.

Perspectives on the role of fospropofol in the monitored anesthesia care setting

Monitored anesthesia care (MAC) is a safe, effective, and appropriate form of anesthesia for many minor surgical procedures. The proliferation of outpatient procedures has heightened interest in MAC sedation agents. Among the most commonly used MAC sedation agents today are benzodiazepines, including midazolam, and propofol. Recently approved in the United States is fospropofol, a prodrug of propofol which hydrolyzes in the body by alkaline phosphatase to liberate propofol. Propofol liberated from fospropofol has unique pharmacological properties, but recently retracted pharmacokinetic (PK) and pharmacodynamic (PD) evaluations make it difficult to formulate clear conclusions with respect to fospropofol's PK/PD properties. In safety and efficacy clinical studies, fospropofol demonstrated dose-dependent sedation with good rates of success at doses of 6.5 mg/kg along with good levels of patient and physician acceptance. Fospropofol has been associated with less pain at injection site than propofol. The most commonly reported side effects with fospropofol are paresthesia and pruritus. Fospropofol is a promising new sedation agent that appears to be well suited for MAC sedation, but further studies are needed to better understand its PK/PD properties as well its appropriate clinical role in outpatient procedures.