Injection bypasses

Vaccines (intramuscular injection bypasses intestinal barrier)... 

Since each of these and other factors may singly or in combination affect absorption, you can see why it is so difficult to specify a drug effect for a person under specific conditions at a given time. This discussion also reaffirms why intravenous injection is the most efficient way to get a drug to its sites of action. Intravenous injection bypasses many factors that may retard absorption because it puts the drug in direct contact with the blood—the vehicle of drug distribution. 

Keywords production decline, economic decline, infill drilling, bypassed oil, attic/cellar oil, production potential, coiled tubing, formation damage, cross-flow, side-track, enhanced oil recovery (EOR), steam injection, in-situ combustion, water alternating gas (WAG), debottlenecking, produced water treatment, well intervention, intermittent production, satellite development, host facility, extended reach development, extended reach drilling. 

Example of a single-channel manifold for use in flow injection analysis where R1 is a reagent reservoir P is the pump S is the sample I is the injector B is a bypass loop ... 

Two examples of dual-channel manifolds for use In flow Injection analysis where R1 and R2 are reagent reservoirs P Is the pump S Is the sample I Is the Injector B Is a bypass loop W Is waste C Is the mixing and reaction coll and D Is the detector. 

Quench Converter. The quench converter (Fig. 7a) was the basis for the initial ICl low pressure methanol flow sheet. A portion of the mixed synthesis and recycle gas bypasses the loop interchanger, which provides the quench fractions for the iatermediate catalyst beds. The remaining feed gas is heated to the inlet temperature of the first bed. Because the beds are adiabatic, the feed gas temperature increases as the exothermic synthesis reactions proceed. The injection of quench gas between the beds serves to cool the reacting mixture and add more reactants prior to entering the next catalyst bed. Quench converters typically contain three to six catalyst beds with a gas distributor in between each bed for injecting the quench gas. A variety of gas mixing and distribution devices are employed which characterize the proprietary converter designs. 

A pipeline that passes around an injection point, valve, control point, heater, steam trap, or other device in order that repairs or other work can be carried out on the bypassed item of equipment as and when required. 

The core - flood apparatus is illustrated in Figure 1. The system consists of two positive displacement pumps with their respective metering controls which are connected through 1/8 inch stainless steel tubing to a cross joint and subsequently to the inlet end of a coreholder 35 cm. long and 4 cm. in diameter. Online filters of 7 im size were used to filter the polymer and brine solutions. A bypass line was used to inject a slug of surfactant solution. Two Validyne pressure transducers with appropriate capacity diaphragms are connected to the system. One of these measured differential pressure between the two pressure taps located about one centimeter from either end of the coreholder, and the other recorded the total pressure drop across the core and was directly connected to the inlet line. A two - channel linear strip chart recorder provided a continuous trace of the pressures. An automatic fraction collector was used to collect the effluent fluids. 

The gas bypassing results obtained from tracer gas injection studies for a flat and a conical distributor plate are shown in Fig. 4. Theflow ratio, FR, is defined as the total gas flow supplied through the draft tube gas supply and the concentric solids feeder divided by the total gas flow supplied through the downcomer gas supply. The A and Y are the actual amounts of gas passing up the draft tube and the downcomer, respectively, determined from the tracer gas injection studies. If FR equals A Y. there is no gas bypassing. If FR is less than A Y. some of the flow supplied through the downcomer gas supply passes into the draft tube. If FR is larger than A/7, the reverse is true. 

Recovery — Recovery control (RC) solutions were prepared in 10/90 v/v ACN/water. Recovery evaluation (RE) samples were prepared in human plasma. Aliquot of RC solutions into assay plates followed sample preparation procedure steps 1 and 2. Instead of adding 50 pL of diluent, wells containing RC solutions were dried down under a steady stream of room temperature N2. The dried wells were then reconstituted with 250 pL of diluent. Reconstituted RC solutions were directly injected onto an HPLC analytical column, bypassing the extraction column. RE samples were aliquoted into an assay plate following normal sample preparation. RE samples were analyzed using the full extraction procedure (with extraction column). The analyte was tested at three concentration levels and the internal standard was tested at one. Mean extraction recovery for fenofibric acid varied from 93.2 to 111.1%, and mean extraction recovery for the Pestanal internal standard was 105.2%. 

The loop injector is a two-position valve that directs the flow of the mobile phase along one of two different paths. One path is a sample loop, which when filled with the sample causes the sample to be swept into the column by the flowing mobile phase. The other path bypasses this loop while continuing on to the column, leaving the loop vented to the atmosphere and able to be loaded with the sample free of a pressure differential. Figure 13.7 is a diagram of this injector, showing both the load and inject positions and the path of the mobile phase in both positions. 

Needleless injections are new devices to bypass this problem. Drugs in powder or liquid form can be injected into the subcutaneous layer in the following ways ... 

In the bypass position, the carrier solution flows through the bypass loop and across the ISFET. The sample is injected into the sampling valve and is introduced into the carrier solution. The bypass loop has a high hydrodynamic resistance and thus the solution proceeds to the detector. The reference electrode is always immersed only in the carrier solution and is electrically connected with the ISFET through the solutioa The apparatus is regularly calibrated by K, Ca and pH standard solutions. 

Drugs need not always be administered orally (i.e., by swallowing), but may also be given parenterally. This route usually refers to an injection, although enteral absorption is also bypassed when drugs are inhaled or applied to the skin. 

Testosterone (T.) derivatives for clinical use. T. esters for im. depot injection are T. propionate and T. heptanoate (or enanthate). These are given in oily solution by deep intramuscular injection. Upon diffusion of the ester from the depot, esterases quickly split off the acyl residue, to yield free T. With increasing lipophilicity, esters will tend to remain in the depot, and the duration of action therefore lengthens. A T. ester for oral use is the undecanoate. Owing to the fatty acid nature of undecanoic acid, this ester is absorbed into the lymph, enabling it to bypass the liver and enter, via the thoracic duct, the general circulation. 17-0 Methyltestosterone is effective by the oral route due to its increased metabolic stability, but because of the hepatotoxicity of Cl 7-alkylated androgens (cholestasis, tumors) its use should be avoided. Orally active mesterolone is 1 a-methyl-dihydrotestosterone. Trans-dermal delivery systems for T. are also available. 

---