Penicillin solution preparation

Penicillin (MM = 356 g/md), an antibiotic often used to treat bacterial infections, is a weak acid. ItsfQis 1.7 X 10-3. Calculate [H+] in solutions prepared by adding enough water to the following to make 725 ml.. 

It is necessary to study stability in solution in the solvent used to prepare sample solutions for injection in order to establish that the sample solution composition, especially the analyte concentration, does not change in the time elapsed between the preparation of the solution and its analysis by HPLC. This is a problem for only a few types of compound (e.g. penicillins in aqueous solution) when the sample solution is analysed immediately after the preparation of the sample solution to be injected. The determination of stability in solution is more of an issue when sample solutions are prepared and then analysed during the course of a long autosampler run. While the acceptance criteria for stabUity in solution may be expressed in rather bland terms by making a statement such as, e.g. the analyte was sufficiently stable in solution in the solvent used for preparing sample solutions for reliable analysis to be carried out , in practice it has to be shown that within the limits of experimental error, the result of the sample solution analysis by the HPLC method is the same for injections at the time for which stability is being validated as for injections immediately subsequent to the sample solution preparation. While this may be done by a subjective assessment of results with confidence limits, strictly speaking a statistical method known as the Student s t-test should be used. 

Penicillenic acids are readily formed in aqueous solutions of penicillins by an intramolecular rearrangement, as described in Sect. C.I.l.a, and they are present in small amounts in almost all penicillin preparations (e.g., Meulenhoff 1965 Seitzinger 1973 Brandt et al. 1974). The rate of formation of penicillenic acid increases strongly with decreasing pH of the penicillin solutions and it shows a high dependence on the inductive effect of the side chain structure of the penicillins (Schwartz and Wu 1966). The compounds are highly reactive with proteins and... 

This exercise can also be done on Whatman LKCigF, 20 X 20-cm preadsorbent plates (Whatman TLC Technical Series, Volume 3). The six individual penicillins are prepared as 1-mg/ml solutions in methanol, and 5 pi of each sample is applied to separate origins on the plate. The mobile phase is methanol-H20-1% NaHC03 (45 55 0.8), and the plate is developed for a distance of 10 cm from the origin in a glass tank that has been preequiUbrated with the mobile phase for 10 min. Time of development is about 70 min. The spots are detected with iodine vapor and the approximate Rf values of the separated penicillins are as follow cloxacillin, 0.18 oxacillin, 0.22 penicillin G, 0.34 methicillin, 0.41 ampicillin, 0.66 and 6-aminopenicillinic acid, 0.82. 

Standard Solution. Prepare daily a standard penicillin working solution in physiological saline or distilled water so that it has a concentration of 10 units... 

Preparations such as lozenges containing sugars as diluents yield erroneous avssays by the standard method. To overcome this, add either an equivalent amount of glucose to the standard penicillin solution or 0 5 per cent of glucose to the assay plate medium. 

The salt was prepared by dissolving the free acid form of the penicillin in the equivalent amount of aqueous sodium bicarbonate and freeze drying the resulting solution. The hydrated salt so obtained was shown by alkalimetric assay to be 94% pure and to contain 6% water. 

Oxidation of phenyl hexyl sulphide with sodium metaperiodate gave also only a trace amount of the corresponding sulphoxide72. On the other hand, Hall and coworkers73 prepared benzylpenicillin and phenoxymethyl penicillin sulphoxides from the corresponding benzyl esters by oxidation with sodium metaperiodate in dioxane solution with a phosphate buffer. A general procedure for the synthesis of penicillin sulphoxides was reported later by Essery and coworkers74 which consists in the direct oxidation of penicillins or their salts with sodium metaperiodate in aqueous solution at pH 6.5-7.0. 1-Butadienyl phenyl sulphoxide 4475 and a-phosphoryl sulphoxides 4576 were also prepared by the same procedure. 

Penicillin was discovered before the war, but could only be prepared in highly dilute, impure, and unstable solutions. Up to 1943, when chemical engineers first became involved with the project, industrial manufacturers used a batch purification process that destroyed or inactivated about two-thirds of the penicillin produced. Within 7 months of their involvement, chemical engineers at an oil company (Shell Development Company) had applied their... 

As mentioned earlier in this chapter, penicillins are very unstable in aqueous solution by virtue of hydrolysis of the p-lactam ring. A successful method of stabilizing penicillins in liquid dosage forms is to prepare their insoluble salts and formulate them in suspensions. The reduced solubility of the drug in a suspension decreases the amount of drug available for hydrolysis. An example of improved stability of a... 

In contrast, parenteral suspensions have relatively low solids contents, usually between 0.5 and 5%, with the exception of insoluble forms of penicillin in which concentrations of the antibiotic may exceed 30%. These sterile preparations are designed for intramuscular, intradermal, intralesional, intraarticular, or subcutaneous injection. Syringeability is an important factor to be taken into consideration with injectable dosage forms. The viscosity of a parenteral suspension should be sufficiently low to facilitate injection. Common suspending vehicles include preserved isotonic saline solution or a parenterally acceptable vegetable oil. Ophthalmic and optic suspensions that are instilled into the eye/ear must also be prepared in a sterile manner. The vehicles are essentially isotonic and aqueous in composition. The reader should refer to Chapter 12 for further discussion on parenteral products. 

Two basic methods are used to prepare parenteral suspensions (a) sterile vehicle and powder are combined aseptically, or (b) sterile solutions are combined and the crystals formed in situ. Examples of these procedures may be illustrated using Penicillin G Procaine Injectable Suspension USP and Sterile Testosterone Injectable Suspension USP. 

Tor [7] developed a new method for the preparation of thin, uniform, self-mounted enzyme membrane, directly coating the surface of glass pH electrodes. The enzyme was dissolved in a solution containing synthetic prepolymers. The electrode was dipped in the solution, dried, and drained carefully. The backbone polymer was then cross-linked under controlled conditions to generate a thin enzyme membrane. The method was demonstrated and characterized by the determination of acetylcholine by an acetylcholine esterase electrode, urea by a urease electrode, and penicillin G by a penicillinase electrode. Linear response in a wide range of substrate concentrations and high storage and operational stability were recorded for all the enzymes tested. 

A pharmacist prepared a solution containing 10 million units of potassium penicillin per 20 mL. How many units of potassium penicillin will a 0.50-mL solution contain ... 

The activity of penicillin G was originally defined in units. Crystalline sodium penicillin G contains approximately 1600 units per mg (1 unit = 0.6 meg 1 million units of penicillin = 0.6 g). Semisynthetic penicillins are prescribed by weight rather than units. The minimum inhibitory concentration (MIC) of any penicillin (or other antimicrobial) is usually given in mcg/mL. Most penicillins are dispensed as the sodium or potassium salt of the free acid. Potassium penicillin G contains about 1.7 mEq of K+ per million units of penicillin (2.8 mEq/g). Nafcillin contains Na +, 2.8 mEq/g. Procaine salts and benzathine salts of penicillin G provide repository forms for intramuscular injection. In dry crystalline form, penicillin salts are stable for years at 4°C. Solutions lose their activity rapidly (eg, 24 hours at 20°C) and must be prepared fresh for administration. 

Penicillins have several properties that are characteristic of /i-lactam antibiotics. They are obtained in relatively pure form as off-white, tan, or yellow freeze-dried or spray-dried solids that are usually amorphous. Alternatively they are sometimes obtained as crystalline solids, often as hydrates. Penicillins do not usually have sharp melting points, but decompose upon heating to elevated temperatures. Most natural members have a free carboxyl group and commercial preparations are generally either supplied as salts, most frequently as sodium salts, or in zwitterionic form as hydrates, e.g.. amoxicillin trihydrate. The acid strength of the carboxyl group in aqueous solution varies from pAT = 2.73 for oxacillin to p= 3.06 for carbenicillin. 

Multi-immunoaffinity chromatography columns were prepared by the coupling of monoclonal antibodies against AMP to activated sepharose. Both sensitivity and specificity were tested for the most commonly used penicillins (AMP, AMO, PenG, OXA, CLO, DICL). Recoveries ranging from 67% to 100% were obtained from phosphate buffer solutions, and it was assumed... 

Procaine salts and benzathine salts of penicillin G provide repository forms for intramuscular injection. In dry crystalline form, penicillin salts are stable for long periods (eg, for years at 4 °C). Solutions lose their activity rapidly (eg, 24 hours at 20 °C) and must be prepared fresh for administration. 

Penicillin can be purified by extraction. The distribution coefficient for penicillin G between isopropyl ether and an aqueous phosphate medium is 0.34 (lower solubility in ether). The corresponding ratio for penicillin F is 0.68. A preparation of penicillin G has penicillin F as a 10.0% impurity, (a) If an aqueous phosphate solution of this mixture is extracted with an equal volume of isopropyl ether, what will be the % recovery of the initial G in the residual aqueous-phase product after one extraction What will be the % impurity of this product (b) Calculate the same two quantities for the product remaining in the aqueous phase after a second extraction with an equal volume of ether. 

The enzyme mixture of 20 ml containing immobilized recombinant penicillin G amidase as the enzyme, 10% hydroxyethyl ester of 4-hydroxy-D-phenylglycine, 4% cefprozil (amine source), and 8% enzyme (immobilized recombinant penicillin G amidase, equivalent to 32 IU/ml of enzyme) was made up without buffer. The above prepared ester solution (6.9 ml) was mixed with water (2 ml) and adjusted to pH 7.5 with 10 N NH4OH. Then the amine source (0.8 g) was added to it and the pH adjusted to 7.5 with 1 N NH4OH and the volume to 18.4 ml. Then the mixture was cooled to 5-15°C and solid enzyme (1.6 g 640 IU) was added to it. The pH was not maintained at 7.5 and fell about 0.6 units during the reaction. The reaction mixture was analyzed by HPLC on a C18 Reverse Phase column. The mobile phase was 10% acetonitrile/0.3% H3P04. The isomers of cefprozil appeared at 2.9 minutes (cis) and at 5.1 minutes (trans). The final product was obtained with a maximum yield of 92-96%. The whole experiment was completed in 25-50 min. 

---