Propofol in a Medium- and Long-Chain Triglyceride Emulsion: Pharmacological Characteristics and Potential Beneficial Effects

Increasing the aqueous solubility of the anesthetic propofol through wormlike micelle formation

Propofol, a phenol derivative, is commonly employed as an intravenous anesthetic during clinical procedures, formulated as an oil/water emulsion due to its poor solubility in water. The stability limitations associated with emulsions have prompted research efforts towards developing aqueous formulations of propofol. In this work, we investigate the solubility enhancement of propofol in anionic and cationic surfactants. Our findings reveal that the solubility of propofol can increase significantly, up to 100-fold, depending on the nature of the micellar aggregate, as observed for alkylammonium halogenates CnTAB (for n = 12, 14 and 16), contrasting with the lower solubility with SDS. Interestingly, C14TAB and C16TAB demonstrate significantly higher solubility than C12TAB. This was attributed to the formation of wormlike micelles, in which the propofol molecules are positioned between the cationic heads of the surfactant molecules, changing the micellar curvature and the morphology of the aggregate. Therefore, the aromatic molecules in the micellar environment can be partitioned into the micellar cores and their palisades. Regarding C12TAB, the alkyl chain is too short to form wormlike micelles, thus, concentrating propofol molecules mainly into the micellar core, and consequently, leading to their aggregation. Solubility diagrams of propofol were constructed in conjunction with different surfactants. The systems exhibiting viscoelastic behavior, indicative of wormlike micelle formation, were further investigated using rheology. Additionally, the fluorescent properties of propofol enabled the examination of the anesthetic molecule within diverse micellar environments.

Pain Intensity at Injection Site during Esophagogastroduodenoscopy Using Long- and Medium-Chain versus Long-Chain Triglyceride Propofol: A Randomized Controlled Double-Blind Study

Background/Aims

The intensities of injection pain resulting from the use of long- and medium-chain triglyceride (LCT/MCT) propofol and conventional LCT propofol during esophagogastroduodenoscopy (EGD) have yet to be compared. We aimed to determine the pain intensity caused by different formulations of propofol and to evaluate the formulation that would be preferred by patients as a sedative agent during their next procedure.

Methods

This study was a single-center, randomized, controlled, and double-blind trial. Pain intensity was estimated 30 seconds after propofol injection by an examiner who was blinded to the group assignment using a numeric (0-10) pain rating scale (NPRS). After 1 week, the patients were asked whether they could recall the pain and were willing to receive the same agent for their next EGD.

Results

One hundred twenty-nine patients were randomly assigned to LCT/MCT or LCT group. Although there was no significant difference in pain incidence between the LCT/MCT and LCT groups (52.9% vs 65.6%, p=0.156), the pain intensity was significantly lower in the LCT/MCT group (NPRS median [interquartile range]; 1 (0-2) vs 2 (0-5), p=0.005). After 1 week, fewer patients in the LCT/MCT group recalled the pain (19.1% vs 63.9%, p<0.001) and more patients in the LCT/MCT group were more willing to use the same agent for their next procedure (86.8% vs 72.1%, p=0.048) than in the LCT group.

Conclusions

LCT/MCT propofol significantly reduced injection pain intensity compared to LCT propofol during EGD and preferred by patients as a sedative agent during their next EGD.

Nanostructured Lipid Carrier of Propofol: a Promising Alternative to Marketed Soybean Oil-Based Nanoemulsion

Nanostructured lipid carrier (NLC) of propofol was formulated using hot emulsification-probe sonication method for improvising its parenteral delivery by reducing pain on injection and risk of microbial contamination. The formulated NLC was optimized using central composite design and evaluated for particle size, zeta potential, morphology, free propofol concentration, hemocompatibility, stability, pain on injection, in vivo anesthetic activity, pharmacokinetics, and antimicrobial effectiveness in comparison to the marketed formulation. Optimized NLCs exhibited globule size, less than 200 nm, and zeta potential - 24.1 mV, indicating its stability. TEM images confirmed the spherical shape and nanosize (200 nm) of optimized NLCs. Free propofol concentration was also found to be 40% lesser than marketed formulation. Optimized NLC was found to be non-hemolytic. Rat paw-lick study showed that propofol NLC was significantly less painful compared to the marketed formulation. Anesthetic potential and pharmacokinetics of optimized NLCs were found to be similar to that of the marketed formulation. NLC was found stable in long-term storage under room temperature. Antimicrobial effectiveness study showed that propofol NLC suppressed microbial growth to a greater extent as compared to the marketed formulation. Hence, the developed propofol NLCs appeared to be clinically useful as a potential carrier for propofol delivery.

Development and evaluation of camptothecin loaded polymer stabilized nanoemulsion: Targeting potential in 4T1-breast tumour xenograft model

Targeted delivery of anticancer agents is poised to improve cancer therapy, for which polymers can serve as targeting ligands or nanocarriers for chemotherapeutic agents. In this study, we have developed and evaluated the efficacy of a camptothecin (CPT)-loaded polymer stabilized nanoemulsion (PSNE) for the passive targeted delivery to breast cancer. Based on the pseudo-ternary phase diagrams, PSNEs were developed using capmul MCM:poloxamer 407 (4:1), solutol HS 15:simulsol P23 (1:2) and water. CPT polymer mixture was developed by solvent evaporation technique. The PSNEs were characterized for droplet size distribution, plasma protein adsorption, drug release, in-vivo targeting potential, hemolytic potential, cytotoxicity, genotoxicity, in-vivo biodistribution and CPT lactone ring stability. The developed PSNEs showed uniform droplet distribution, extended drug release (76.59±6.12% at 24h), acceptable hemolytic potential, significant cytotoxicity (IC₅₀=176±4.3ng/mL) and genotoxicity against MCF-7 cancer cells but low DNA damage potential in human peripheral blood lymphocytes. The efficiency of PSNEs for the targeted delivery of CPT into the tumour regions was documented in 4T1-breast tumour xenografted BALB/c mice. In-vivo biodistribution study shows that 7105.84±568.46ng/g of CPT was passively targeted from PSNE to breast cancer tissue. About 80% of the lactone form was stable for 24h. Taken together, our study provides a promising strategy for developing PSNE-targeted drug delivery system for the breast cancer therapy.

Effect of Lipid Composition in Propofol Formulations: Decisive Component in Reducing the Free Propofol Content and Improving Pharmacodynamic Profiles

Current endeavor was aimed towards studying significance of lipid composition on free propofol concentration in aqueous phase and associated pain on injection. Three different nanoformulations, namely long-chain triglyceride (LCT)/medium-chain glyceride (MCG)-based nanoemulsion (ProNano), MCG-based self-nanoemulsifying formulation (PSNE), and lipid-free nanoformulation (PNS) were accessed for the same. In vitro and in vivo performances of developed formulations were compared with Diprivan®. ProNano showed minimum free propofol concentration (0.13%) and hence lower pain on injection (rat paw-lick test, 6 ± 2 s) compared to Diprivan®, PSNE, and PNS (0.21%, 0.23%, and 0.51% free propofol, respectively, and rat paw-lick test; 12 ± 3, 14 ± 2, and 22 ± 3 s, respectively). These results conjecture the role of MCG in effective encapsulation of propofol. Anesthetic action assessed by measuring duration of loss of righting reflex (LORR), which was found similar in case of ProNano and PSNE (14 ± 3 and 15 ± 3 min, respectively) compared to Diprivan® (13 ± 3 min). In case of lipid-free formulation, PNS, extended anesthetic action (21 ± 2 min) was observed which may be due to sustained release of propofol from nanosponges. Studies on effect of lipoproteins on propofol release highlighted significance of HDL (100% release with maximum concentration of about 1.2 μg/ml of HDL) from all three formulations.

Acute effects of general anesthesia with propofol, pentobarbital or isoflurane plus propofol on plasma metabolites and hormones in adult pigs

Experimental setups for physiological research, in which acute operative interventions need to be performed, can require inclusion of general anesthesia (GA), which may interfere or confound with the effects of the experimental factors of interest on measured variables. It was recently shown that the most commonly used sedatives/anesthetics in pigs (e.g., ketamine, xylazine, azaperone) affect physiological responses and thus the primary metabolic readouts have the potential to be confounded. To extend the search for a physiologically-friendly anesthesia regime for such studies, we investigated effects of GA induced by propofol (Prop) or pentobarbital (Pent) or propofol plus isoflurane (Prop + Isof) on plasma concentrations of commonly measured metabolites and hormones. In 2 experimental runs, 6 female pigs fitted with jugular vein catheters were used. Fasted pigs received either no drug (CON) or anesthetized rotationally either with Prop, Pent or Prop + Isof on different days, separated with washout periods of sufficient length (2 to 3 d). Six-h profiles of glucose, lactate, non-esterified fatty acids (NEFA), triglycerides (TG), cholesterol, urea as well as hormones including glucagon, insulin and cortisol were determined. Concentrations of cholesterol, urea and glucagon remained unaffected by any of the treatments ( > 0.05). Pent tended to increase cortisol from 30 to 90 min after drug administration. Glucose and lactate concentrations were increased ( < 0.05) by Prop and Pent within the first hour of GA ( < 0.05). Propofol and Pent reduced NEFA concentrations, which were more pronounced during the last 2 h of the studied period. Triglyceride concentrations were increased by all 3 agents within the first 45 min with Prop containing treatments exerting a stronger effect than Pent. Our data suggest that GA with Prop and particularly with Pent adulterate plasma metabolite and hormone profiles of pigs acutely, and thus has the potential to confound the effects of experimental factors of interest. Although Prop + Isof anesthesia did not differ from the controls, providing a physiologically-friendly GA, both single and the isoflurane-combined treatment of Prop induced hypertriglyceridemia due to the lipid adjuvant of the Prop drugs. It is concluded that readouts obtained under GA may be influenced both by physiological adulterations as response to anesthesia as well as by artifacts due to accompanying ingredients of the drug formulations.

New medications and techniques in ambulatory anesthesia

Novel anesthetic and analgesic agents are currently under development or investigation to improve anesthetic delivery and patient care. The pharmacokinetic and analgesic profiles of these agents are especially tailored to meet the challenges of rapid recovery and opioid minimization associated with ambulatory anesthesia practice.

Get to the point in intensive care medicine--the sooner the better?

Timing of therapy plays a pivotal role in intensive care patients. Although being evident and self-explanatory, it has to be considered that the appropriateness of a specific therapeutic intervention is likewise important. In view of antibiotic therapy of critically ill patients, the available evidence supports the concept of hitting hard, early (as soon as possible and at least before the onset of shock) and appropriately. There is increasing evidence that a positive fluid balance is not only a cosmetic problem but is associated with increased morbidity. However, prospective studies are needed to elucidate whether a positive net fluid balance represents the cause or the effect of a specific disease. Since central venous pressure (CVP) is an unreliable marker of fluid responsiveness, its clinical use to guide fluid therapy is questionable. Dynamic hemodynamic parameters seem to be superior to CVP in predicting fluid responsiveness in hemodynamically unstable patients. Sedation is often used to facilitate mechanical ventilation. Since there is no best evidence-based sedation protocol, weaning strategies should take the risk of iatrogenic arterial hypotension secondary to high doses of vasodilatory sedative agents into account. In this regard, the concept of daily wake-up calls should be challenged, because higher cumulative doses of sedatives may be required. The right dose and timing for renal replacement therapy is still discussed controversially and remains a subjective decision of the attending physician. New renal biomarkers may perhaps be helpful to validate when (and how) renal replacement therapy should be performed best. Last but not least, all therapeutic interventions should take the individual co-morbidities and underlying pathophysiological conditions into account.

[Agents for sedation and analgesia in the intensive care unit]

Sedation-analgesia for critically ill patients is usually performed with the combination of a sedative agent and an opioid. Midazolam and propofol are the agents most commonly used for sedation in ICU. The quality of the sedation is quite comparable with both agents, but pharmacokinetic properties of propofol allow a more rapid weaning process from mechanical ventilation. However, implementation of algorithms to adjust drug dosages reduces ventilator days and limits the kinetic differences between propofol and midazolam. Among the adverse events associated with propofol, propofol infusion syndrome is a rare but lethal aspect of propofol therapy. Opioids are the mainstay of analgesic therapy. They interact synergistically with hypnotics. Sufentanil, fentanyl and morphine are the most frequently used opioids. Remifentanil is an ultrashort acting opiate that does not appear to accumulate with prolonged use. The advent of remifentanil has allowed the use of analgesia-based sedation.