Dispensing techniques (compounding and good practice)

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Dispensing techniques (compounding and good practice)




Study Points



image Practical aspects of dispensing


image The working environment and procedures


image Extemporaneous dispensing equipment and its correct use


image Manipulative techniques used in dispensing and compounding


image Ingredients and their selection


image Problem-solving in extemporaneous dispensing



Introduction


This chapter deals with some of the practical aspects of dispensing, concentrating on the small-scale manufacture of medicines from basic ingredients. This process is called compounding or extemporaneous dispensing. Additionally, good practice which applies to all aspects of dispensing will be considered.


Nowadays, most medicines are manufactured by the pharmaceutical industry under well-controlled conditions and packaged in suitable containers designed to maintain the stability of the product (e.g. sealed in an inert atmosphere). Extemporaneous dispensing, which cannot be as well-controlled, should only be used when a manufactured product is unavailable. Reasons for unavailability of products may include:



The pharmacist undertaking extemporaneous dispensing has a responsibility to maintain equipment in working order, to ensure that the formula and dose are safe and appropriate and that all materials are sourced from recognized pharmaceutical manufacturers. There are also requirements concerning calculations, maintaining good records and labelling. Any staff involved in the process should be adequately trained. These requirements should all be incorporated within standard operating procedures (SOPs, see Ch. 11).


In any dispensing process, the end-product will be used or taken by a person or an animal. Therefore, it is important that the medicine produced is of the highest achievable quality. This, in turn, means that the highest standards must be applied during the preparation process.



The working environment and procedures




Cleanliness and hygiene


The dispensing bench, the equipment, utensils and the container which is to hold the final product must all be clean. Lack of cleanliness can cause contamination of the preparation with other ingredients. For example, a spatula which has been used to remove an ingredient from one container will adulterate subsequent containers if not washed before being used again. Cleanliness will also minimize microbial contamination.


Dispensing staff should have a high standard of hygiene and hand-washing facilities should be readily available. A clean overall should be worn, hair tied back and, preferably, be covered with a disposable hat/cap and any skin lesions covered with a dressing. Disposable gloves should be worn during preparative work and discarded afterwards. Consideration should be given to the use of masks if volatile substances or fine powders are to be handled.




Equipment


Not only is the selection of the correct equipment for the job essential, but the equipment must be used in the correct way and maintained in good order.



Weighing equipment


Weighing equipment can be divided into non-automatic and automatic weighing equipment. Non-automatic weighing equipment requires an operator to place and/or remove the items from the balance pan. Such weighing equipment can be a mechanical beam balance, which has a pan on one end of the beam for weights and a pan on the other end of the beam for the material to be weighed (Fig. 30.1) or it can be an electronic top-pan balance, in which case the substance to be weighed is placed on the pan and an electronic display gives the weight. Automatic weighing equipment is designed to automatically fill a package to the required weight without the intervention of an operator. Such equipment is used in the pharmaceutical industry, and nowadays for extemporaneous dispensing. Whichever type of weighing equipment is used, it must be suitable for its intended use and be sufficiently accurate. In the UK, weighing equipment must be calibrated in metric units and must be marked with maximum and minimum weights that can be weighed.




General rules for the use and maintenance of weighing equipment


The following points are important to ensure accurate weighing:



image Balances must be placed on a level surface; most will incorporate a level indicator device to allow adjustment for a non-level surface


image Balances’ readings must indicate zero, before use. If zero is not indicated, then incorrect readings, and hence weights, may be obtained


image Strong draughts, caused by air conditioning or a breeze, can affect some balances and make a correct reading impossible. Therefore always site a balance in a draught-free area


image Always keep the balance pan clean and free from debris


image Regular checks with stamped weights should be made to ensure the balance is working correctly


image If possible keep a record of when, and by whom, the check was carried out, as well as the result


image Never weigh less than the declared minimum weight or more than the maximum weight declared on the balance


image Do not weigh ingredients on a piece of paper, as this introduces a potential inaccuracy. The exception is when weighing greasy or semi-solid materials, e.g. white soft paraffin, when a counterbalanced piece of paper should be used


image Always read the manufacturer’s instructions before using an electronic balance


image Use tweezers to handle weights, if used. Never handle weights, as this will affect their accuracy and risks contamination.

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Jun 24, 2016 | Posted by in PHARMACY | Comments Off on Dispensing techniques (compounding and good practice)

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