Pharmaceuticals, Chemistry tutorial

Introduction:

Pharmaceuticals are the compounds prepared or manufactured for use as medicinal drugs. They are made either synthetically or biosynthetically. The main manufactured groups comprise antibiotics like penicillin, tetracycline, streptomycin, chloramphenicol and anti-fungal.  Antibiotics are the chemical substances which can slow down the growth of and even demolish harmful micro-organisms.

Antibiotics:

Antibiotics are the specific chemical substances derived from or produced via living organisms which are able of slowing down the life processes of other organisms. The first antibiotic was introduced in the year 1896 by Ernest Duchene and rediscovered via Alexander Fleming in the year 1928 from Penicillium notatum. There are over 10,000 different antibiotics known whereas around 200 are in commercial use. The Antibiotics are known to be the most prescribed drugs. Antibiotics are prepared on an industrial scale by using a variety of fungi and bacteria. Illustrations comprise penicillin, amoxicillin, ampicillin, streptomycin, chloramphenicol, tetracycline, cephalosporin, vancomycin and so on.

Production of Penicillin:

Penicillin was the primary naturally occurring antibiotic discovered. This can be obtained in a number of forms from Penicillium moulds. It is not a single compound however a group of closely associated compounds, all having the similar basic ring-like structure (a β-lactam) derived from the two amino acids (namely: valine and cysteine) through a tripeptide intermediate. The third amino acid of this tripeptide is substituted via an acyl group (R). Penicillin can be found in two distinct types: Natural and Semi-synthetic. Penicillin-G is the most strong of all penicillin derivatives. Antibiotics are prepared on an industrial scale by employing a variety of fungi and bacteria. Penicillin is prepared or manufactured by the fungus, Penicillium chrysogenum that needs lactose, other sugars and a source of nitrogen in the medium to grow well. Penicillin similar to all antibiotics is a secondary metabolite; therefore it is only produced in the stationary phase. It needs a batch fermenter and a fed batch procedure is generally employed to prolong the stationary period and therefore increase production. The industrial production of penicillin can be categorized into three stages which are:

  • Inoculum build up phase
  • Growth phase
  • Penicillin production phase

Media Formulation:

  • Lactose: 1%
  • Calcium Carbonate: 1%
  • Corn steep liquor: 8.5 %
  • Glucose: 1%
  • Phenyl acetic acid: 0.5 g
  • Sodium hydrogen phosphate: 0.4 %
  • Antifoaming agent: Vegetable oil

At the beginning of the fermentation procedure, a number of spores will be introduced to a small conical flask (250 to 500 ml) where it will be incubated for several days. The most desired parameter at this phase is explosive growth; therefore the medium in the flask will have high amounts of simply utilizable carbon and nitrogen sources like starch and corn steep liquor. At this phase, the spores start to revive and form vegetative cells. The conical flask is put on a shaker to enhance oxygen diffusion in the flask. Once the total conditions for growth have been established and there is a viable vegetative culture active within the flask, it will be transferred to a 1 or 2 litre bench top reactor. This reactor will be fitted to allow better observation of the culture as compare to when it was in the flask. The cells at this point are expected to be showing filamentous morphology. After a moment, the medium being added to the reactor changes. Carbon and nitrogen will now be added sparingly next to precursor molecules for penicillin fed-batch style. It is significant to note that the presence of penicillin in the reactor is itself inhibitory to penicillin production.

Therefore, it is significant to have an efficient process for the elimination of this product and to maintain the constant volume in the reactor. The penicillin then undergoes downstream processing. The penicillin product requires being very pure, as it is being employed as a therapeutic medical drug, therefore it is dissolved and then precipitated as a potassium salt to separate it from the other substances in the medium. This can then be refined and packaged for marketing and distribution.

Production of Acetylsalicylic acid (Aspirin):

Acetylsalicylic acid or aspirin is one of the popular pain-relieving drug (that is, analgesic) developed in the late 19th century as a household medicine for aches and pains. Aspirin tablets are manufactured in various shapes. Their size, weight, thickness and hardness might differ based on the amount of the dosage. The lower and upper surfaces of the tablets might be flat, round, convex or concave to different degrees. The tablets might as well encompass a line scored down the middle of the outer surface; therefore the tablets can be broken in half, if desired. The tablets might be engraved by a symbol or letters to recognize the manufacturer. 

The synthesis of aspirin is categorized as an esterification reaction, where the alcohol group from the salicylic acid reacts by an acid derivative (that is, acetic anhydride), resulting methyl acetyl ester and acetic acid as the by-product. Small amounts of sulphuric acid are often employed as a catalyst.  The main reactor for the procedure is a glass-lined 1500 gallon tank fitted by a water-cooled reflux condenser, thermometers having automatic temperature registers and an efficient agitator. The reactor is charged by mother liquor. The mother liquor is made by dissolving 1532 kilograms of acetic anhydride in 1200 kilograms of toluene. The toluene is a solvent that doesn't participate in the reaction and therefore can be recovered later and reused. 1382 kilograms of salicylic acid is added to the mother liquor in the reactor. The reaction mixture is heated to between 88 and 92 degrees Celsius. It is kept at this temperature for 20 hours. Subsequently, the reaction mixture is transferred to aluminum cooling tanks and is allowed to cool for 3 to 4 days. By the end of cooling the mixture has reached room temperature, around 15 to 25 degrees Celsius. 

At this point, the acetylsalicylic acid has precipitated as big regular crystals. The mother liquor is now taken out via filtration or centrifuging to separate out as much liquid as possible. The filtrate will be a solution of around 180 to 270 kilograms of un-precipitated acetylsalicylic acid, 510 kilograms of acetic anhydride, 600 kilograms of acetic acid and 1200 kilograms of toluene. The acetic acid is achieved as a by-product of the acetylation step of the process. Next, ketene gas is passed via the recycled filtrate at a temperature of 15 to 25 degrees Celsius. The gas is introduced to a well agitated reactor by using a diffusion plate or sparger. This carries on till there is a weight increase of 420.5 kilograms of ketene is noticed. At this point, the mother liquor includes 180 to 270 kilograms of unprecipitated acetylsalicylic acid and 1532 kilograms of acetic anhydride in 1200 kilograms of toluene. The mother liquor is recycled and 1382 kilograms of salicylic acid is added to carry on the reaction cycle. The acetylsalicylic acid that was extracted after the initial reaction is washed with distilled water until all the acetic acid is eliminated. It is then pressed or centrifuged as dry as possible and then dried more via a current of warm air at 60 to 70 degrees Celsius. The result of pure acetylsalicylic acid is between 1780 to 1795 kilograms per batch for this reaction procedure. Documentation on each and every batch is kept all through the manufacturing procedure and finished tablets undergo some tests before they are bottled and packaged for the distribution. 

Production of Tetracycline:

Tetracyclines are the antibiotics that are produced via the pharmaceutical industry. Pfizer were the original producers of the first tetracyclines and are the major choice whenever the proprietary band is prescribed. 

The production of antibiotics is stated to be a batch procedure, as contamination would be more likely in a continuous process. However a continuous procedure is quicker, the wastage caused via contamination signifies it is not a cost efficient procedure. Fermentation is employed to let the chosen microorganisms to multiply and produce the antibiotic on a big scale. The chosen organism that produces the antibiotic is isolated and a starter culture is formed to increase the number of available organisms. Subsequently, the medium is transferred to fermentation tanks where the microorganisms are allowed to grow and multiply, therefore large amounts of the antibiotic are formed. After a number of days a maximum level of antibiotic will have been produced via the microorganisms and separation of the products can start. Various different purification processes can be employed example: organic chemicals, leaving a purified powder. This entire process takes a few days meaning huge quantities can be manufactured each and every year worth millions of pounds to the producers.

Various formulations are then produced like tablets, capsules, intravenous drips. The kind of formulation will influence how much the drug will cost the customer. For illustration, tablets are the cheapest as they are the simplest to produce and they are joined by cheap materials and chemicals in formulation. On the other hand, an intravenous preparation will be more costly as a solvent is employed to dissolve the drug. In the production method of tetracycline, the main cost of the materials is in the production of the fermentation culture. It includes necessary ingredients that the microorganisms require for growth and reproduction. Most significantly, there will be a carbon source (that is, molasses or sugars). Nitrogen is as well necessary mostly in metabolic pathways that occur in the organism. The other elements like phosphorus, iron and copper are as well essential. These are added as salts. As well, to prevent foaming throughout fermentation, anti-foaming agents like octadecanol are used.

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