Modeling solute sorption into plastic tubing during organ perfusion and intravenous infusions

A comparison of the pharmacokinetic and pharmacodynamic properties of nitroglycerin according to the composition of the administration set: A preliminary study

BACKGROUND

There is a risk of drug sorption into an intravenous administration set composed of polyvinyl chloride (PVC), polyurethane (PU), or polyolefin (PO). This has implications on the dose of the active ingredient the patient receives, and thus therapeutic success. This study aimed to determine the plasma concentration of nitroglycerin and the effect of nitroglycerin on patients based on the composition of the administration set.

METHODS

Using a randomized, open-labeled, 3 × 3 crossover method, 9 volunteers were assigned to 3 groups. In period I, nitroglycerin (100 μg/mL) was infused via a PVC- (group A), PU- (group B), or PO-based (group C) administration set. In period II, PU- (group A), PO- (group B), and PVC-based (group C) administration sets were used, and in period III, PO- (group A), PVC- (group B), and PU-based (group C) administration sets were used. The rate of drug administration in all periods was 12 mL/hour for 30 minutes using an infusion pump. Blood samples were collected, and the plasma concentrations of nitroglycerin were analyzed using validated high-performance liquid chromatography coupled with tandem mass spectrometry. Blood pressure was determined using a sphygmomanometer applied to the other upper arm at an interval of 5 minutes.

RESULTS

We observed that the mean plasma concentration of nitroglycerin over time when administered using a PO-based tube was higher than that when using a PU- or PVC-based tube. When the percent change of the mean arterial pressure from baseline at each time point was compared among groups, there were statistically significant differences between PU and PO or PVC at most points during nitroglycerin infusion.

CONCLUSION

Our results showed higher nitroglycerin plasma concentration and lower arterial pressure when a PO-based administration set was used than when a PVC- or PU-based administration set was used. PO-based administration sets may be more appropriate for nitroglycerin administration compared to those composed of PVC or PU.

Evaluation of tacrolimus sorption to PVC- and non-PVC-based tubes in administration sets: Pump method vs. drip method

Tacrolimus sorption to tubes was evaluated using pump and drip methods For tubes, polyvinylchloride (PVC)- and non-PVC-based (polyurethane [PU] and polyolefin [PO]) tubes were used. First, inner surface properties of tubes were analyzed using field emission scanning electron microscopy and X-ray photoelectron spectroscopy. Tacrolimus was quantitatively analyzed using high-performance liquid chromatography with UV detection. For kinetic sorption analysis, diluted tacrolimus to 10μg/mL was passed through 1-m-long tubes at 10mL/h. Samples were collected at 1-4h. The inner surface of PO-based tubes was relatively smooth and soft compared with those of PVC- and PU-based tubes. Atomic compositions of tubes matched chemical formulas of polymers excluding low-level impurity in PVC-based tubes. Tacrolimus was successfully analyzed and linearly determined at 2.5-20μg/mL. From both methods, PVC- and PO-based tubes exhibited the highest and the lowest (<10%) sorption levels to tacrolimus, respectively. Tacrolimus was stably delivered using the pump method. Results suggested that the pump method can estimate tacrolimus sorption in administration set tubes and evaluate other sorptional drugs used at low concentrations. PO-based tubes also have promising potential as an alternative for administration set tubes.

Evaluation of Drug Sorption to PVC- and Non-PVC-based Tubes in Administration Sets Using a Pump

Administration sets are delivery tools for the direct application of drugs into the body and are composed of a spike, a drip chamber, tubes, Luer adapters (connectors), a needle cover for protection, and other accessories. Drug sorption to tubes of administration sets is a critical issue in terms of safety and efficacy. Although drug sorption is an important factor in the quality of an administration set, there are no standard evaluation methods for the regulation of drug sorption to the tubes. Here, we describe an evaluation protocol for drug sorption to tubes of administration sets. Tubes made of polyvinyl chloride (PVC)- and non-PVC-based polymeric materials were cut to 1 m in length. Diazepam and tacrolimus were used as model drugs. In the kinetic sorption study, we selected the drug concentration and flow rate based on the clinical usage of these drugs. After the dilution of each drug in a glass bottle, the diluted drug solution was delivered through tubes of administration sets using a pump. Samples were collected in amber vials at appropriate time points and the drugs were analyzed using high-performance liquid chromatography. Drug concentrations and sorption levels to tubes of the administration sets were calculated. Acceptable criteria to ensure the quality of administration sets are recommended.

Sorption of unoprostone isopropyl to packaging materials

This study investigated the stability of an ophthalmic solution formulation of unoprostone isopropyl (UI), a prostaglandin like compound, in two types of packaging materials, polypropylene (PP) and low-density polyethylene (LDPE). We determined the concentration of UI and its degradation products as a function of time and found that the rate of disappearance of drug was faster for the formulation stored in LDPE bottles than that stored in PP bottles. Further studies indicated that the inferior stability observed with the LDPE packaging was primarily due to the sorption of UI to the packaging material and to a lesser degree, chemical degradation. The sorption was temperature dependent, lowering the temperature reduced the sorption, thus improving the shelf-life of the product.

Sorptive loss of volatile and gaseous anesthetics from in vitro drug application systems

In in vitro pharmacological experiments, determination of effective concentration values for various anesthetics depends on understanding the exact concentration of the drugs dissolved in physiological solutions. Actual anesthetic concentration may differ from expectations because of drug adsorption, absorption or other loss, especially in tubing. We tested the hypothesis that delivered concentrations of anesthetics decrease when solutions pass through laboratory tubing and investigated such loss by measuring the entering and exiting dissolved concentrations of two volatile (sevoflurane and isoflurane) and two gaseous (nitrous oxide and xenon) anesthetics. We tested solutions passed through tubes (1 m x 2 mm ID x 4 mm OD) made of five different materials (glass, Teflon, polyethylene (PE), polyvinyl chloride (PVC), and silicon rubber). Exiting concentrations of anesthetics were significantly reduced when they were passed through PVC (>33%) and silicon (>43%) tubes. There were no decreases in anesthetic concentrations with glass, Teflon, or PE tubes. When sevoflurane solution flowed through PVC and silicon tubes, it took 20 and 30 min, respectively, after start of flow until the anesthetic loss became negligible. These results indicate that frequently used PVC and silicon tubes, whereas flexible and easy to handle, have serious drawbacks when used in inhaled anesthetic pharmacology experiments.

Adsorption of xenobiotics to plastic tubing incorporated into dynamic in vitro systems used in pharmacological research--limits and progress

Commonly used materials incorporated into dynamic culture systems typically show the feature of adsorption of lipophilic xenobiotics. Yet, this phenomenon is strongly limiting the use of dynamic culture models and ex vivo organ perfusions in pharmacological and toxicological research. The aim of the study was to characterize different materials with respect to their capacity for drug adsorption and to find methods or materials to reduce the loss of substrate by adsorption in order to improve the use of dynamic in vitro systems. The adsorption of different xenobiotics (lidocaine, midazolam, lormetazepam, phenobarbital, testosterone, ethoxyresoroufine) to tubes used in dynamic in vitro systems (polyvinyl-chloride, silicone) were investigated and compared to a new material (silicone-caoutchouc-mixture). In addition, the role of protein deposition onto the tubing was studied and it was investigated whether it was possible to reach saturation of the inner tube surface by pre-loading it with the test compound. We found that silicone tubes provided the highest comfort with respect to handling and reusability, but they also demonstrated the highest capacity for substrate adsorption. Polyvinyl-chloride was the second best in handling but also demonstrated a high complexity in its adsorption behavior. The silicone-caoutchouc-mixture reached acceptable experimental results with respect to its handling and demonstrated a very low capacity for substrate adsorption.

Analysis of a diffusion dryer for the respiratory delivery of poorly water soluble drugs

PURPOSE

The purpose of this study was to analyze a diffusion dryer as a means to remove organic solvents from aerosol particles of poorly water soluble drugs.

METHODS

Aerosols of methanol, ethanol, and ethyl acetate were generated with an ultrasonic nebulizer, and inflow to outflow concentration ratio of vapor in a annular charcoal column was determined as a function of time by gas chromotography at two to four different airflow rates. In addition, the particle transmission efficiency was determined with an ethanol solution of the test compound, budesonide. The results were analyzed with equations originally developed for assessing the loss of drug from intravenous tubing along with independent measures of the adsorption isotherm of the vapors onto charcoal.

RESULTS

Aerosol production was relatively constant with time, and the transmission of solid particles through the column occurred with efficiency nearing 100%. The inlet to outlet vapor concentration ratio was adequately described by a model of three resistances in series composed of the inner tube, the screen mesh, and the charcoal bed.

CONCLUSIONS

The diffusion dryer was found to be satisfactory for the removal of methanol, ethanol, and ethyl acetate and the efficiency may be assessed from the adsorption isotherms on charcoal and the geometry of the dryer.

Short-term chronoamperometric screening of chlorpromazine-package interactions

A new electroanalytical method has been developed to measure and predict solute sorption interactions with solid surfaces. By maximizing surface-to-volume ratios, this method significantly reduces the study time of drug-package interactions and allows prediction of possible long-term effects. Chronoamperometry experiments were run in 40 microL drops of solution containing drug placed on a solid substrate disk of about 7 mm diameter in a sample cell designed to accommodate a miniaturized three-electrode setup. Logarithmic current signatures obtained by computing Delta(ln i)/Delta(ln t) were used to define the experimental conditions necessary to avoid the kinetic complications of chlorpromazine oxidation in the interpretation of the results of the chronoamperometric analysis. Results of sorption studies of chlorpromazine to glass, polypropylene, high density polyethylene, poly(ethylene terephthalate), ethylene vinyl acetate, and poly(vinyl chloride) are presented. The small volume sorption experiments demonstrated that chlorpromazine interacts most quickly with PVC and HDPE and least with glass and polypropylene. Long term stability tests confirmed these predictions, thereby indicating that the small volume method makes drug-package interaction studies feasible in early development. The generation and analysis of Delta(ln i)/Delta(ln t) signature curves extends the usefulness of the electroanalytical method to other systems by accurately identifying the appropriate time domains for steady state or Cottrell behavior.