Tablets colouring

No change of the tablet colour during 3 months at 30 °C and 70% relative humidity. 

R. cajfra Sonder. From this S. African species Koepfli isolated three alkaloids (A) forming hair-like needles, m.p. 294-5°, (B) crystalline, but uncharacterised and rauwolfine, C20H26O3N2 2-5H2O, which forms buff-coloured tablets, decomposes at 235-8° (vac.), and dissolves in sodium hydroxide, though not in sodium carbonate solution. Rauwolfine chloride, C20H25O2N2CI. H2O, forms faintly pink plates, m.p. 297-300° or 300-3° (dry, dec.), + 29° (H2O) or + 45° (EtOH). 

Baugh and co-workers exposed solutions of phenylbutazone to the light of a projector lamp in the presence of typical dyes used to colour sugar-coated tablets. Erythrosine sodium photosensitized decomposition of the drug via, it was suggested, singlet oxygen [134]. 

OO A chemist adds a few drops of deep violet-red iodine solution to a vitamin C tablet. The iodine solution quickly becomes colourless. Then the chemist adds a solution that contains chlorine, CI2. The chemist observes that the violet-red colour of the iodine reappears. Explain the chemist s observations, in terms of redox reactions. 

The need for placebos generally from the first human study onwards t)q)ically involves manufacture of dummy capsules or tablets, and if oral solutions or suspensions are to be used, these must be matched as closely as possible for taste, colour and appearance. 

In addition to these regulatory issues there are some homemade limitations to common quality documentation (e.g. normally, pharmaceutical companies prefer to market tablets in polyethylene bottles in the United States, in contrast to blister packs for the European market and different trade names, colours or pack sizes are also unavoidable in certain cases). The consequence of these differences is the fact that a common Module 3 (Quality) and therefore a common Quality Summary in Module 2 cannot be compiled. 

If you have done some clinical work you may have noticed that digoxin tablets come in two dose sizes - 0.25 mg (usually white), and 0.0625 mg (or 62.5 microgram - often blue in colour). One brand name is Lanoxin PG . Did you know that the PG stands for paediatric-geriatric which recognizes the immature kidneys of the infant and the failing kidneys of the elderly and the need to give smaller doses at both ends of life to avoid digoxin toxicity ... 

Ion pair titration using a coloured indicator complex is used in pharmacopoeial assays of dicyclamine elixir, procyclidine tablets, sodium dodecyl sulphate and cetrimide emulsifying ointment. 

Colourants obviously have the potential to interfere in analysis beeause they are efficient absorbers of UV/visible radiation. In tablets and capsules, colours tend to be organometallic dyes or metal oxides which are not appreciably soluble in any of the solvents used for extraction and can be filtered off with other insoluble matrix constituents. When capsules are analysed the coloured outer shell is removed before the contents of the capsule is extracted. 

Ion pair extraction provides a standard method for estimating ionic surfactants either colorometrically or titrimetrically. For example a cationic surfactant such as cetrimide can be estimated by pairing it with a lipophilic anionic dye such as bromocresol purple. The ion pairing creates a coloured lipophilic ion pair, which can be extracted into an organic solvent such as chloroform and a quantitative measurement of the colour extracted can be made spectrophotometrically. This type of assay is described in the BP for Clonidine Injection and Benzhexol Tablets. 

After 2 weeks at room temperature no change of the colour of the tablets was observed but the long term compatibility between aminophylline and lactose should be controlled. 

A colourant pigment should be added to obtain a homogeneous appearance of the tablets. 

Start with formulation No. 1 by means of the manual sugar coating procedure during some hours. After changing to formulation No. 2 continue with the same procedure until homogeneous coloured sugar coated tablets are obtained. 

Trimethyl tellurium bromide, (CH3)3TeBr, is obtained from the /3-base and hvdrobromic acid. It forms large, transparent, colourless tablets, slowly decomposing between 250° and 280° C., readily soluble in cold water but almost insoluble in organic solvents. The neutral solution in water contains bromine ions, and gives no precipitate or coloration with colourless hydriodic acid. It unites with ferric chloride. giving a complex which crystallises as salmon-coloured needles and forms a complex salt with stannic bromide. 

AG Fogg, AA Barros, JO Cabral. Differential-pulse adsorptive stripping voltametry of food and cosmetic synthetic colouring matters and their determination and partial identification in tablet coating and cosmetics. Analyst 111 831—835, 1986. 

An additional benefit of SORS is the suppression of surface-generated fluorescence which has an identical spatial (but not temporal) distribution to the Raman signal of the surface layer. This feature is particularly beneficial in situations where intense surface-layer fluorescence masks the underlying Raman signal examples include melanin-induced fluorescence in biological tissue in vivo and intensely coloured capsules or coated tablets in pharmaceutical applications. 

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