Pharmaceutics
From Pharmpedia
Pharmaceutics is the subject that deals with the technology of preparation of medicines. This technology utilises scientific principles, specially a number of physico chemical principles and consists of a high degree of "art". A drug,solid or liquid cannot be given as it is, i.e, in its pure state because of many reasons such as
1.The taste is usually not palatable
2.Pure powders do not "flow" well, so cannot be prepared into formulations
3.Formulation into tablets or capsules or some other formulation ensures drug content uniformity, easy packing, easy transport, storage and administration.
4.Pure drug may have to be protected from environment or stabilised.
So a medicine is a formulation of a drug and the "making" or manufacture of such a formulation is dealt with in the subject called pharmaceutics.
The technology called pharmaceutics has its roots in the mortar and pestle of the apothecary of the 1900-1950 period. In that period the doctors ordered (gave prescriptions) to apothecarys or pharmacists to prepare medicines and gave directions for it. The pharmacists were adept in the technology of making medicines which was also known as compounding.
Gradually several changes took place in the field of medicines; the volume of medicines to be made increased enormously, the usage methods and routes of administration increased, the importance of aseptic procedures was understood with the progress in microbiology, the storage time increased from a few days to a few years and the role of the doctor also changed from that of a family physician to a professional practitioner. So as they say "old order changeth, yielding place to new" and the art of compounding receded into history yielding place to the science of formulation development and the technology of drug manufacture.
Pharmaceutics mainly deals with the manufacture of medicines. The designing of an appropriate dosage form for a drug, carrying
out preformulation studies, stability studies, scale up studies, starting production batches and
carrying out production as per validated, quality assured, standard operating procedures-all comes into the purview of
pharmaceutics. This is the main angle, the main river. There are many streams that join this big river and are only extensions of
the river. The physical chemistry involved in the manufacture of
medicines, the old type and the new type of dosage forms, the traditional and the modern rules of dispensing, incompatibilities
which are also called as pharmaceutical drug interactions, the unit operations involved in the manufacture of drugs, the
body-dosage form interaction studied as biopharmaceutics-are all different angles of pharmaceutics.
Pharmaceutics is the heart of any pharmacy course. In this respect, there is a very big difference (that is easily perceived) between the western countries and countries like India. In India B.pharm and M.Pharm are centered on pharmaceutics and they train students as candidates for the pharmaceutical industry. In the west, the colleges are focussed on pharmacy practise and train students to enter into the pharmacy profession. Since pharmaceutics is the technology of making medicines and since this really is the most important aspect or the "end use" of pharmacy this subject is usually given number one position by the students and very high credits by the teachers.
Pharmaceutics, also called as pharmaceutical technology is a major discipline and comprises of many branches. The subjects taught under this specialisation in B.Pharm are : physical pharmacy, manufacturing pharmacy, dispensing pharmacy, pharmaceutical engineering, and Biopharmaceutics and pharmacokinetics.
Contents |
Physical pharmacy
Physical pharmacy is the subject that deals with the physico chemical principles involved in drug manufacture. Students learn here the basics of Atomic and molecular structure, physical properties of matter (dielectric constant, refractive index, optical rotation), states of matter and phase Equilibria, solutions of electrolytes and solutions of Non-Electrolytes, the laws of Thermodynamics, Ionic equilibria, Surface tension and Viscosity, Buffer solutions and Isotonicity and Electromoty force, measurement of pH etc. All these are usually covered in paperI of physical pharmacy. In paper II more advanced and applied chapters such as Interfacial tension, surfactants, theoretical aspects of formation of suspensions and emulsions, complexation, adsorption, reaction kinetics,rheology etc. are dealt with. Physical pharmacy is a very interesting and lively subject. Theory has a lot of depth,requiring the usage of our grey cells to understand the principles and practicals are very very interesting and demanding-they demand good skills and patience.What the subject does is-it helps you to design an effective safe and stable formulation.For example "isotonicity" chapter will tell you that injecting a hypotonic or hypertonic solution into a patient's blood can cause either the swelling or the crushing of red blood cells and can cause dangerous results-so isotonicity calculations help in designing an intravenous solution for a medicine. Physical Pharmacy by Alfred Martin,Physical Pharmacy by C.V.S.Subrahmanyam,Physical Chemistry by Bahl and Thuli are some very good text books for this subject.In addition Remingtons pharmaceutical sciences gives a good idea of all the concepts and perusing physical chemistry books will be of immense use.
Manufacturing pharmacy or Industrial Pharmacy
Manufacturing pharmacy or Industrial Pharmacy deals with the methods of preparation of medicines. This is also usually taught in two stages. In stage I,that is paper I, the traditional methods of manufacture such as maceration, infusion, decoction, percolation and traditional dosage forms such as tinctures, Aromatic waters, syrups, mucilages spirits, elixirs, magmas are taught. In stage II of manufacturing pharmacy the modern formulations such as tablets, capsules, parenterals, suppositories and semislids-their design, formulation considerations and manufacturing considerations are dealt with. Modern machinery used in manufacture of medicines is also introduced here. The theory and practise of Industrial pharmacy by Lachman and Lieberman, pharmaceutics by Aulton, pharmaceutics by Ansel, Remington's pharmaceutical sciences are good books that deal with the subject in a very exhaustive manner. Manufacturing pharmacy or Industrial pharmacy is the king among all pharmaceutics subjects, it is the heart of pharmaceutical technology.
Dispensing pharmacy
Dispensing pharmacy introduces to a student the old formulae used in medicine and the old principles. But what is undeniable is that the principles are valid even today, even in large scale manufactute, only their expression has changed. In Dispensing Pharmacy the compounding and dispensing in a systematic manner of various preparations like powders, mixtures, ointments and creams, emulsions and suppositories is taught. Under each class several sub classes will be there and several principles of preparation are to be understood. For example, powders are to be prepared after understanding the principles of content uniformity, geometric dilution, trituration and proper packing. In emulsion preparation a primary emulsion is first prepared and then made upto volume. Labelling of dispensed medicines is extremely specific and requires a lot of care. Incompatibilities is one big chapter in dispensing which deals with physical, chemical and therapeutic incompatibilities such as precipitation, change of colour and evolution of gases like carbon di oxide. Even if we are not dispensing any medicines today, all the principles involved in the manufacture as well as incompatibilities are very very relevant even today, if we uderstand them we can design our formulations better. Dispensing pharmacy by Cooper and Gunn is a very good book that clearly brings out all the principles involved in dispensing. Today's pharmaceutical care involving patient counselling among other things which is being taught as a part of pharmacy practise, we may say is an extrapolation of the principles used in dispensing such as warning about incompatibilities (drug interactions) and following general dispensing procedure (warning about side effects, explaining dosage regimen etc.).
Pharmaceutical Engineering
Pharmaceutical Engineering deals with unit operations such as drying, milling, mixing, filteration, crystallisation, evaporation and distillation which are all used mostly in the bulk drug manufacture but to a little extent in the formulation industry also. The student also learns in this subject some important engineering considerations such as fluid flow, heat transfer, mass transfer, refrigeration and humidity. The understanding of these concepts makes a pharmacy graduate very efficient in operations such as monitoring air handling units, distillation and evaporation units, heating and cooling viscous masses or semisolids etc. Over all a person who is strong in pharmaceutical engineering tackles affairs in the pharmaceutical industry much better than one whose knowledge is restricted to pharmacy operations.
The equations Q = UA( delta t)
where Q is the amount of heat transfered
U is the over all heat transfer coefficient
A is the area across which heat transfer is taking place and delta t is the temperature differential across which heat transfer is taking place.
This is a very important equation, the understanding of which helps us to achieve good heat transfer for a specific system having a particular area of heat transfer. U, the overal all heat transfer coefficient is dependent on the overall resistance to heat transfer offered by the unit and two surface coefficients. These three components can be managed and the U and through that the Q can be increased to a high degree by someone who has the proper understanding of heat transfer concepts . Physical pharmacy gives the foundation of physical principles over which Pharmaceutical Engineering builds the edifice of unit operations, heat transfer and mass transfer. Together they make a pharmacy graduate an excellent technologist. Chemical Engineering by Badger and Banchero, Theory and Practice of Industrial pharmacy by Lachman and Liberman, pharmaceutics by Aulton, Pharmaceutical Engineering by K.Samba Murthy, Pharmaceutical Engineering by C.V.S.Subrahmanyam and Pharmaceutics by Rawlins are all good books for this subject.
Biopharmaceutics and Pharmacokinetics
Biopharmaceutics and Pharmacokinetics is a subject of realtively recent origin. When one Cardiologist was making rounds of his wards he found that patients receiving the same dosage regimen of cardiac drugs were showing very different responses. When he further searched for causes he discovered that those who were simultaneously taking pain medication such as phenylbutazone were showing altered response to cardiac therapy. This type of incidents started the search into the causes of different responses to same treatment and the science of biopharamaceutics and pharmacokinetics took birth. Biopharmaceutics deals with several factors that effect theabsorption (A), distribution (D), metabolism (M) and elimination (E) of drugs, such as physico chemical properties of the drug, dosage form factors, biological factors etc.
Pharmacokinetics deals with the time course of action, or rate and extend of ADME of drugs. Understanding this subject helps in planning a proper dosage regimen and in designing drug delivery systems. Understanding drug interactions also helps in giving proper patient counselling. For eample no calcium containing additive should be used in formulating tetracycline-because tetracycline will complex with calcium and will become unavailable in the stomach. Biopharmaceutics and Pharmacokinetics books written by Gibaldi, Swarbrick, Notari and Clinical Pharmacokinetics by Parthasaradhi are very good books for this subject.
Author
This article is contributed by Smt. Prof. Jayanti Vijaya Ratna .
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