Compounding is the act of preparing, mixing, assembling, packaging, and/or labeling a drug or device as the result of a practitioner’s prescription drug order

Historical Pharmaceutical Preparations

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Historical Pharmaceutical Preparations

Bougies

Bougies are solid preparations that are designed to be inserted into the urethra, nose or ear in order to exert a local or systemic effect in a similar manner to the modern suppository.

The urethral bougie was generally formulated in glycerinated gelatin and was designed to be pencil shaped, with a point at one end. Generally a glycogelatin 2 g bougie was approximately 7 cm in length, whereas, a 4 g version was 14 cm long. If a bougie was compounded using Theobroma Oil as a base, then its weight was approximately half that of an equivalentsized bougie formulated in a gelatin base. The gelatin versions were better than those moulded in oil as they were more flexible, which aided insertion into the urethra. If a firmer consistency of the bougie was required then acacia mucilage could be substituted for either glycerin or water in the formulation.

Henry Wellcome devised a version of the urethral bougie with an elongated bulb near the tip that reputedly reduced the likelihood of involuntary expulsion on insertion.

The mould for the urethral bougie had to be warmed before pouring the mass in order to facilitate complete filling. Finished bougies were then often rolled in lycopodium powder after removal from the mould in order to stop them sticking to surfaces. Glycogelatin bougies had to be protected from excessively dry or moist air by storing in a tightly closed container in a cool place in order to maintain their integrity.

Nasal bougies were similar to urethral bougies but shorter, approximately 2.5 cm in length, and weighed approximately 1.5 g. They were usually prepared using a glyco-gelatin base as this was more suitable for the medicaments that were to be incorporated into the product.

Cachets (capulae amylaceae, oblata)

Cachets were developed from the early practice of masking the taste of unpleasant bitter or nauseating drug powders by encapsulating the offending substance in bread and jam. Developments from this practice involved the production of thin wafer sheets from flour and water which could be dried and stored. In order to administer a powder the dry wafer was floated on water. When it had softened, a tablespoon was passed underneath the wafer and it was lifted out. The powder was then placed into the spoon-shaped depression and the corners of the wafer folded over to enclose it. Water was then poured onto the spoon and the packet swallowed.

In its most well-developed form a cachet comprised two lenticular or spoon-shaped flanged discs made from rice paper. The drug substance was placed within the saucer-shaped depression in one half of the cachet and was sealed in by placing the second half on top. A cachet could be sealed by moistening the flanges, usually by quickly passing them over a piece of wet felt, and then sticking them together (wettype seal). Sophisticated sets of apparatus were devised for the filling and sealing of larger numbers of cachets.

These included pourers to avoid powder contaminating the flange of the cachet and specialised holding and sealing devices.

Collodions

These are liquid preparations, intended for external use, containing highly volatile solvents (usually a base solution of pyroxylin (soluble gun-cotton) in a mixture of ether and alcohol) that evaporate to leave either a mechanical or a therapeutic film. Collodions had to be applied to the skin using a soft brush. Although almost obsolete, Flexible Collodian BP and Salicylic Acid.

Decoctions (decocta)

A decoction differs from an infusion in that one or more crude drug bases, either whole or suitably prepared, were boiled with water for a specified time, usually 10 minutes or until a given volume was obtained. The preparation was then strained and, if necessary after cooling, made up to volume with more distilled water, which was passed through the original filter to ensure that as much extract as possible had been removed from the marc. This process left an aqueous preparation similar to ‘clear soup’. If decoction was followed by evaporation, then a solid or semi-solid extract was produced.

Where a number of ingredients were to be included in the decoction then they were added at different times during the process. Hard ligneous drugs were added first, with the addition of aromatics and volatile oils near the end of the process in order to minimise loss of active principles.

The object of a decoction was to produce an aqueous solution containing soluble active drug principles that were not degraded by heat. Clearly few drugs were suited to preparation in this manner.

Extracts (extracta)

Extracts are produced by the action of various solvents (aqueous, alcoholic, ethereal, acetic or ammoniated), using a variety of processes (expression, maceration, decoction, percolation), which may be followed by evaporation with or without vacuum assistance to produce liquid, semi-solid or solid products. Where the juices of fresh plants were obtained by expression and evaporation, the resultant extracts were frequently termed succi spissati (inspissated juices).

Extracts were intended to contain the active principles of crude drugs while minimising the amount of inert matter present. In general, extracts contained a higher proportion of active drug principles than equivalent infusions, decoctions or tinctures. The most common extracts encountered were either solid or liquid extracts.

Solid extracts varied in consistency depending on their degree of concentration. They were termed either soft extracts, with a consistency between that of a pill mass and a paste, or dry extracts. Soft extracts were semi-sticky masses formed by concentration from a liquid extract. They have fallen from current use because it was difficult to standardise the degree of ‘softness’ and therefore their consistency with any degree of accuracy. In addition, soft extracts often hardened on storage, producing a tough mass that was difficult to handle. This also means that the strength of a soft extract could vary significantly depending on preparation and storage.

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Dry extracts replaced soft extracts as the solid extract of choice as these could be standardised, they varied less in strength and were generally easier to handle. Storage was less likely to cause significant problems, although granular dried extracts were preferred to those that were powders, as powdered varieties were more likely to absorb moisture from the air and become a solid block.

Liquid extracts are still commonly used in extemporaneous compounding, the main example being Liquid Liquorice Extract BP. Liquid extracts are usually prepared by the ‘reserve percolate process’

Eye discs (lamellae)

Lamellae were small discs of a glyco-gelatin base that were intended to be placed onto the cornea of the eye, where they would be allowed to dissolve in the lachrymal secretions. The active ingredient, which was often an alkaloid, would be released for a local effect.

Solid extracts varied in consistency depending on their degree of concentration. They were termed either soft extracts, with a consistency between that of a pill mass and a paste, or dry extracts. Soft extracts were semi-sticky masses formed by concentration from a liquid extract. They have fallen from current use because it was difficult to standardise the degree of ‘softness’ and therefore their consistency with any degree of accuracy. In addition, soft extracts often hardened on storage, producing a tough mass that was difficult to handle. This also means that the strength of a soft extract could vary significantly depending on preparation and storage.

Galenicals

Most of the active constituents of traditional extemporaneously prepared products originated from plant or animal sources. Although it was likely that the therapeutic effects of these preparations could be attributed to one active ingredient, isolation of discrete active constituents was either technologically impossible or prohibitively expensive. In addition, it was commonly believed by early practitioners that under certain circumstances, extraneous constituents present in impure forms of medicines could exert beneficial actions on the therapeutic ingredients. This is why various galenicals, which evolved before the ability to separate active ingredients accurately, became commonplace in pharmaceutical compounding.

Today, ‘galenicals’ is a term that is applied loosely, and often incorrectly, to name any type of preparation (elixirs, solutions, waters, etc.) irrespective of whether it is an extract of a crude drug or a solution of chemicals. Historically, however, true galenicals were pharmaceutical preparations obtained by macerating or percolating crude drugs with alcohol of an appropriate strength or some other solvent (menstruum), which was carefully selected to remove as completely as possible only the desired active components, leaving the inert and other undesirable constituents of the plant in the solid phase (marc).

The ancient Greek physician Galen (Claudius Galenus of Pergamum, AD 131–201) was the first to devise solutions of the active constituents of plants, hence the term galenicals. Since that time, pharmacists have tried to improve upon Galen’s techniques and prepare galenicals that are stable, free from inert material and therapeutically efficacious as well as concentrated, for ease of handling. Examples of true galenicals include decoctions, extracts, infusions, tinctures, vinegars and oxymels. Aromatic waters, although not true galenicals, will also be outlined in the following sections.

Glycerins (glycerita or glycerites)

These were produced by dissolving or incorporating substances in glycerin (or glycerin solutions). The principal use of glycerins was to provide a simple and rapid method of producing an aqueous solution of a drug that was not otherwise readily soluble. Many of the glycerins were made in a concentrated form that could be easily diluted with water or alcohol without precipitation

Infusions (infusa)

Infusions are dilute solutions containing the watersoluble extracts of vegetable drugs. They were prepared by macerating drugs in water for short periods of time, varying from 15 minutes to 2 hours. The volume of the product depends on the quantity of menstruum retained by the marc, which should not be pressed. The degree of comminution of the drug, the temperature used for the preparation of the infusion and the length of maceration chosen depended upon the nature of the drug and the constituents to be extracted.

Infusions were usually prepared in earthenware vessels (latterly glass was used). The drug was added to the vessel usually suspended in some way or enclosed in muslin (like a modern teabag) so as to be just below the surface of the water. If the drug sank to the bottom of the vessel the mixture would need occasional stirring. If hot water was added to prepare the infusion it would be weighed into a previously tared and warmed vessel to prevent cracking of the measure. Often a layer of cloth was wrapped around the infusion container in order to reduce heat loss and hence aid the extraction process. When the specified infusion time had elapsed, the product was strained and the marc removed as quickly as possible so as to allow the preparation to cool before use. The supernatant formed the infusion, which was generally unstable and needed to be Freshly Prepared.

Mucilages (mucilagines)

Mucilages are thick, viscous, adhesive aqueous solutions or extractions of gums. There are two official mucilages: Mucilage of Acacia BP (BP 1953, page 854) and Mucilage of Tragacanth BPC (BPC 1949, page 924) that are used as thickening agents in medicines for internal use. Mucilages were traditionally used as suspending agents for insoluble substances in mixtures. They have also been used to thicken the continuous phase of an oil-in-water emulsion system. A mucilage of starch has been used for its emollient effects on the skin and other mucilages have been used as water-miscible bases for dermatological preparations and as lubricating agents for catheters and some surgical instruments.

Since mucilages are prone to decomposition they should not be made in quantities greater than required.

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