Manufacture of highlighted intagliated articles

Process for manufacturing colored solid articles, e.g. pharmaceutical tablets, bearing at least one highlighted intagliation, which comprises (1) either (A) applying to said articles a film coating suspension comprising at least one defined optically anisotropic substance and at least one film coating agent, or (B) applying to said articles a suspension comprising at least one defined optically anisotropic substance but no film coating agent, and then (2) spraying the resulting articles with a solvent, and in which both of the steps (1) and (2) are carried out in a conventional film coating apparatus.

This invention relates to an improved process for manufacturing intagliated 
articles in which the intagliations are highlighted. 
In our European patent application No. 82300586.3 (Publication No. 60023 
Al) there is described and claimed inter alia a process (hereinafter 
referred to generally as Process A) for the manufacture of coloured solid 
articles, for example medicinal tablets, bearing at least one highlighted 
intagliation, which comprises applying to coloured (i.e. non-white) 
intagliated articles a film coating suspension comprising at least one 
optically anisotropic substance having a minimum refractive index not 
greater than 2.00 and at least one film coating agent, the process being 
carried out in a conventional film coating apparatus in such a way that a 
rubbing action takes place between the articles being coated. 
In United Kingdom patent application No. 8216816, there is described inter 
alia a process (hereinafter referred to generally as Process B) for the 
manufacture of coloured solid articles, for example medicinal tablets, 
bearing at least one highlighted intagliation, which comprises applying to 
coloured intagliated articles a suspension comprising at least one 
optically anisotropic substance having a minimum refractive index not 
greater than 2.00, but no film coating agent, in a suitable liquid, the 
process being carried out in a conventional film coating apparatus in such 
a way that a rubbing action takes place between the articles being coated. 
It is to be understood that in this specification the expression 
"intagliated article" means a solid article, for example a tablet, which 
has at least one figure, mark or notation, or any combination thereof, cut 
into or formed in the surface of the article by a compression punching, 
incision or engraving procedure, or by any other procedure which produces 
a like effect. Furthermore, in this specification the expression 
"optically anisotropic substance" means a substance which exhibits 
different refractive indices in different directions. 
In the highlighted products of the abovementioned Processes A and B there 
is a distinct contrast between the intagliation(s) and the remainder of 
the article. However, we have found that on occasions the said products 
have a slightly dusty appearance which tends to reduce the contrast 
between the intagliation(s) and the remainder of the article. This is 
somewhat more prevalent when the highlighting process is carried out on a 
fairly large scale in a relatively large coating machine, for example a 60 
inch Accela-Cota (obtainable from Manesty Machines PLC, Speke, Liverpool 
24, England). We have now made the surprising discovery, and herein lies 
the basis of this invention, that highlighted products of superior 
appearance, in which there is better contrast between the intagliation(s) 
and the remainder of the article, are obtained if a spray procedure is 
employed after the highlighting step. 
According to the invention there is provided a process for the manufacture 
of coloured solid articles bearing at least one highlighted intagliation, 
which comprises: 
(1) either (A) applying to coloured intagliated articles, which themselves 
may be uncoated or film coated, a film coating suspension comprising at 
least one optically anisotropic substance having a minimum refractive 
index not greater than 2.00 and at least one film coating agent, the 
application being carried out in a conventional film coating apparatus in 
such a way that a rubbing action takes place between the articles being 
coated; 
or (B) applying to coloured intagliated articles, which themselves may be 
uncoated or film coated, a suspension comprising at least one optically 
anisotropic substance having a minimum refractive index not greater than 
2.00, but no film coating agent, and the application being carried out in 
a conventional film coating apparatus in such a way that a rubbing action 
takes place between the articles being coated; 
and characterised in that: 
(2) the resulting coloured solid articles bearing at least one highlighted 
intagliation are sprayed with a solvent in a conventional film coating 
apparatus in such a way that a rubbing action takes place between the said 
articles. 
The process of this invention is capable of wide application. Thus, for 
example, it can be used in the pharmaceutical or veterinary field, for 
example in the manufacture of pharmaceutical or veterinary unit dosage 
forms, for example pharmaceutical tablets or veterinary tablets (also 
known as boluses), bearing at least one highlighted intagliation, or in 
the sugar confectionery field, for example in the manufacture of 
highlighted pieces of sugar confectionery, for example sweets or candy, 
having approximately the same dimensions as a pharmaceutical tablet. 
Process A can be summarised as follows: 
(1) the articles used as the starting material are coloured intagliated 
articles of the appropriate dimensions, for example coloured intagliated 
pharmaceutical tablets; 
(2) there is applied to the coloured intagliated articles a film coating 
suspension (hereinafter "the highlighting coating suspension") comprising 
at least one optically anisotropic substance having a minimum refractive 
index not greater than 2.00, and at least one film coating agent; 
(3) the highlighting coating suspension is applied to the coloured 
intagliated articles in conventional manner in a conventional film coating 
apparatus in such a way that a rubbing action takes place between the 
articles being coated. 
The coloured intagliated articles used as the starting material in Process 
A may be uncoated or they may be film coated. In the latter case the film 
coat may comprise any known film coating agent, for example a cellulose 
ether, for example hydroxypropyl methylcellulose or ethylcellulose, or 
cellulose acetate, shellac or an acrylic resin, or a mixture thereof. It 
may also contain one or more known film coating adjuvants, for example a 
plasticiser, for example glycerol, and/or a surface active agent and/or a 
wax. The film coat is applied in conventional manner in a conventional 
film coating apparatus, using either an organic solvent-based process, for 
example a process involving a mixture of methylene dichloride and 
methanol, or an aqueous process. The film coating apparatus may, for 
example, be a coating pan, or a coating drum, for example a side-vented 
perforated drum coating machine, or a so-called Wurster coating apparatus 
(a fluidized-bed coating apparatus). 
The colour which characterises the said coloured intagliated articles used 
in Process A may be present throughout the articles or it may be applied 
to the surface thereof. Thus, for example, a colouring agent may be 
applied in the form of a colouring film coating solution or suspension to 
the surface of white articles. Any colouring agent which is approved for 
the purpose in question, for example pharmaceutical purposes, may be used, 
for example iron oxide (red, yellow or black), carmine, a natural dye, for 
example turmeric or betacarotene, a water-soluble dye, for example 
tartrazine, or an aluminium lake of a water-soluble dye, optionally in 
admixture with at least one opaque white pigment, for example titanium 
dioxide. 
The optically anisotropic substance is used in the form of a powder. As 
suitable optically anisotropic substances there may be mentioned, for 
example, white optically anisotropic substances, for example known 
transparent white pigments (also known as "extender" or "inert" white 
pigments), for example aluminium hydroxide, china clay (kaolin), talc, 
calcium carbonate or barium carbonate. Other suitable optically 
anisotropic substances are magnesium carbonate (light or heavy form), cane 
sugar (sucrose), lactose or tartaric acid. Alternatively, in the case of a 
medicinal tablet or a bolus the medicinal or veterinary agent present 
therein may also be used as the optically anisotropic substance. That is, 
the medicinal or veterinary agent may be used in a dual role: as both the 
active agent in the tablet or bolus and as the optically anisotropic 
substance. 
Suitable film coating agents for use in the highlighting coating suspension 
are mentioned above. 
As aforesaid, the optically anisotropic substance has a minimum refractive 
index not greater than 2.00. The choice of this substance depends upon the 
film coating agent applied therewith, in that an optically anisotropic 
substance should be used which has a minimum refractive index which is the 
same as or similar to the refractive index of the film coating agent. It 
is an advantage to use an optically anisotropic substance which has a 
maximum refractive index which is as different as possible from its 
minimum refractive index, as this affords the best visual results. Details 
on typical materials which can be used are as follows: 
______________________________________ 
Film coating agents Refractive index 
______________________________________ 
Methylcellulose 1.50 
Ethylcellulose 1.47 
Hydroxyethylcellulose 
1.51 
Hydroxypropylcellulose 
1.56 
Hydroxypropyl methylcellulose 
1.49 
Sodium carboxymethylcellulose 
1.52 
Cellulose acetate 1.48 
Shellac 1.52 
Acrylic resin 1.48 
______________________________________ 
Optically anisotropic 
Refractive indices 
substances Minimum Maximum 
______________________________________ 
Aluminium hydroxide 
1.50 1.56 
Kaolin 1.56 1.57 
Talc 1.54 1.59 
Calcium carbonate 1.51 1.65 
Calcium sulphate 1.57 1.61 
Barium carbonate 1.53 1.68 
Magnesium carbonate 
1.51 1.70 
Cane sugar 1.54 1.57 
.alpha.-Lactose 1.52 1.57 
Tartaric acid 1.50 1.61 
______________________________________ 
The amount of optically anisotropic substance that is applied depends upon 
the degree of colour contrast required, the refractive indices of the 
substance, and its particle size. Thus, for example, in the case where the 
film coating agent is hydroxypropyl methylcellulose and the intagliated 
tablets used as starting material carry a film coat which is coloured with 
red or black iron oxide, the amounts of optically anisotropic substance 
which are used (expressed as % w/w of tablet weight) vary between 0.1 and 
1.0%. In the case of corresponding tablets which carry a film coat 
coloured in more pastel shades, the said amounts vary between 0.5 and 
5.0%. Approximately three times as much heavy magnesium carbonate, 
compared to light magnesium carbonate, is required to achieve the same 
effect. 
The highlighting coating suspension used in Process A may optionally 
contain one or more film coating adjuvants which are conventional in the 
film coating art, for example plasticisers, for example glycerol, 
propylene glycol, polyethylene glycol, diethyl phthalate, glyceryl 
monostearate or castor oil, and surface active agents, for example 
polyoxyethylene sorbitan monooleate [`Tween` (Trade Mark) 80], and waxes, 
for example beeswax or carnauba wax. In addition, the said mixture may 
optionally contain at least one colouring agent, for example one or more 
of the specific colouring agents mentioned above. The net effect of this 
is that the colours in question [i.e. the colour of the main body of the 
article and the colour of the intagliation, on the one hand, and the 
colour of the highlighting coat, on the other] interact in a subtractive 
manner (see Encyclopaedia Britannica, Micropaedia, Volume III, 1974, 22). 
Numerous colour combinations are thus possible, the intagliation normally 
being seen as a pale version of the coloured highlighting coat. If the 
colour of the main body of the article and that of the highlighting coat 
are so-called complementary colours (see above reference), the main body 
of the article is seen as black and the intagliation is seen as a pastel 
colour (i.e. a pale version of the colour of the highlighting coat). 
The highlighting coating suspension used in Process A may be an organic 
solvent-based suspension, for example where the solvent is a mixture of 
methylene dichloride and methanol, or it may be an aqueous suspension. 
When all of the ingredients are watersoluble, they should be applied in an 
organic solvent-based suspension. 
The above outline of Process A applies mutatis mutandis to Process B except 
that in the latter case there is applied to the coloured intagliated 
articles a suspension containing at least one optically anisotropic 
substance having a minimum refractive index not greater than 2.00, but no 
film coating agent, in a suitable liquid. In the case where the coloured 
intagliated articles used as starting material have no film coating agent 
on their surface, or where they have a relatively water-soluble film 
coating agent, for example hydroxypropyl methylcellulose, on their 
surface, a suitable liquid is, for example, water or a mixture of a 
polyhalogenated (1-4C)alkane and a (1-4C)alkanol, for example a mixture of 
methylene dichloride and methanol. In the case where the said coloured 
intagliated articles have a relatively water-insoluble film coating agent, 
for example ethylcellulose, on their surface, a suitable liquid is an 
organic solvent, for example a polyhalogenated (1-4C)alkane, for example 
methylene dichloride, or a dialkyl ketone of not more than 6 carbon atoms, 
for example acetone. In the case where the liquid is water, at least one 
surface active agent, for example polyoxyethylene sorbitan monooleate 
[`Tween` (Trade Mark) 80], may optionally be present. In the case where 
the liquid is water or a mixture of a polyhalogenated (1-4C)alkane and a 
(1-4C)alkanol, at least one humectant, for example glycerol, propylene 
glycol or a low molecular weight polyethylene glycol, for example 
polyethylene glycol 300, may optionally be present. In the case where the 
liquid is an organic solvent, there may optionally be present a 
plasticiser which is appropriate for the film coating agent in question, 
for example a di-(1-4C)alkyl phthalate, for example diethyl phthalate. 
In a preferred embodiment of Process B the application of the 
above-mentioned suspension, containing at least one optically anisotropic 
substance having a minimum refractive index not greater than 2.00, is 
followed by the application in conventional manner of at least one film 
coating solution or suspension comprising at least one film coating agent, 
optionally at least one film coating adjuvant, and optionally at least one 
colouring agent. 
The solvent used in the spray step (i.e. step 2) which characterises this 
invention depends upon the water-solubility of any film coating agent on 
the outer surface of the highlighted articles. If the film coating agent 
is relatively water-soluble, for example hydroxypropyl methylcellulose, or 
where there is no film coating agent on said outer surface, a suitable 
solvent is, for example: 
(a) water; 
(b) a mixture of water and a (1-4C)alkanol, for example methanol or 
ethanol; 
(c) a mixture of a polyhalogenated (1-4C)alkane, for example methylene 
dichloride, and a (1-4C)alkanol, for example methanol; or 
(d) a mixture of solvent (c) and a dialkyl ketone of not more than 6 carbon 
atoms, for example acetone. 
The said solvent (a), (b), (c) or (d) may optionally contain at least one 
humectant, for example glycerol, propylene glycol or a low molecular 
weight polyethylene glycol, for example a polyethylene glycol having a 
molecular weight in the range 190 to 600, for example polyethylene glycol 
300. It is surprising that, when a humectant is used, the highlighted 
products are not sticky or tacky at the end of the process. 
In the case where the film coating agent on said outer surface is 
relatively insoluble in water, for example ethylcellulose, shellac or an 
acrylic resin, a suitable solvent is, for example: 
(e) a polyhalogenated (1-4C)alkane, for example methylene dichloride; 
(f) a dialkyl ketone of not more than 6 carbon atoms, for example acetone; 
(g) a mixture of solvents (e) and (f); or 
(h) a mixture of solvent (g) and a (1-4C)alkanol, for example methanol. 
The said solvent (e), (f), (g) or (h) may optionally contain at least one 
plasticiser which is known in the art to be a suitable plasticiser for the 
film coating agent in question, for example a di-(1-4C)alkyl phthalate, 
for example diethyl phthalate or di-n-butyl phthalate, or an ester of 
glycerol with an alkanoic acid, for example glyceryl triacetate or 
glyceryl monostearate, or a vegetable oil, for example castor oil. 
The spray step which characterises this invention is carried out under the 
conventional film coating conditions which are appropriate for the solvent 
in question and the film coating apparatus in question. 
It is to be understood that, if desired, as a final step the highlighted 
products of this invention may be polished in conventional mannner using 
at least one wax, for example beeswax or carnauba wax, so as to impart an 
attractive appearance thereto. 
The invention is illustrated but not limited by the following Examples:

EXAMPLE 1 
A mixture of tablets, consisting of 10 kg. of white intagliated 10 mg. 
propranolol hydrochloride tablets (average weight 95 mg.) and 350 kg. of 
white intagliated placebo tablets (average weight 95 mg.), was treated as 
follows: 
(a) Colour coating step 
A clear coating solution was made up, which consisted of the following: 
______________________________________ 
hydroxypropyl methylcellulose 
8.4 kg. 
[`Pharmacoat` (Trade Mark) 606, 
Shin-Etsu Chemical Company Ltd., 
Tokyo, Japan] 
glycerol 1.68 kg. 
deionized water 63 l. 
______________________________________ 
9 liters of this clear coating solution were set aside for use in the 
highlighting step (see below). The following were added to the remainder 
of the clear coating solution: 
______________________________________ 
pink pigment dispersion 5.4 kg. 
[`Opaspray` (Trade Mark) M-1-1399B, 
Colorcon PLC, Orpington, Kent, England] 
deionized water to 108 l. 
______________________________________ 
There was thus obtained a colour coating solution. 
The above-mentioned mixture of tablets was film coated with the colour 
coating solution in a side-vented perforated drum coating machine (60 inch 
Accela-Cota) under the following conditions: 
______________________________________ 
inlet air temperature 
70-75.degree. C. 
outlet air temperature 
51-54.degree. C. 
process airflow 4100 ft..sup.3 min..sup.-1 
chamber vacuum -0.4" w.g. 
spray rate 660-700 ml. min.sup.-1 
atomizing air pressure 
70-73 psi 
drum speed 4 r.p.m. for 
first hour, 
4.5 r.p.m. for 
final 1.5 hours 
______________________________________ 
There was thus obtained a mixture of pink, film coated, intagliated 
tablets. 
(b) Highlighting step 
A highlighting coating suspension was prepared as follows: 
Powdered light magnesium carbonate (1.296 kg.) was thoroughly dispersed in 
deionised water (9 l.). To the suspension were added the above-mentioned 9 
l. of the clear coating solution [see section (a)], the resulting 
suspension was made up to 42 l. with deionised water, and then thoroughly 
mixed until homogeneous. 
The above-mentioned mixture of pink, film coated, intagliated tablets was 
film coated with the highlighting coating suspension in the 60 inch 
Accela-Cota under the conditions described in section (a) except that the 
drum speed was 5 r.p.m. There was thus obtained a mixture of highlighted 
tablets. 
(c) Solvent spray step 
As soon as the highlighting step was completed, deionised water (20 l.) was 
sprayed on to the tablets under the same conditions as were used in the 
highlighting step. When all of the water had been applied, the drum was 
stopped and the tablets removed. There was thus obtained a mixture of 
highlighted tablets of excellent appearance. 
EXAMPLE 2 
(a) Highlighting step 
10 kg. of a mixture of coloured film coated intagliated placebo and 
medicinal tablets (weight range 95-640 mg.) were heated to 60.degree. C. 
in a side-vented perforated drum coating machine (24 inch Accela-Cota). 
One liter of a 3.3% w/v aqueous solution of hydroxypropyl methylcellulose 
[`Pharmacoat` (Trade Mark) 606], containing 0.65% w/v glycerol and light 
magnesium carbonate (30 g.) suspended therein, was applied continuously at 
50 ml. min..sup.-1 by means of a low pressure air-spray unit. The drum 
speed was kept at 16 r.p.m. and the temperature of the inlet air at 
60.degree. C. When all of the suspension had been applied, the drum was 
stopped and the tablets removed. There was thus obtained a mixture of 
coloured film coated tablets with intagliations highlighted in white. 
(b) Solvent spray step 
The mixture of highlighted tablets was heated to 60.degree. C. in a 
side-vented perforated drum coating machine (24 inch Accela-Cota), and a 
1% w/v aqueous solution of polyethylene glycol 300 (200 ml.) was applied 
continuously at 50 ml. min..sup.-1 by means of a low pressure air-spray 
unit. The drum speed was kept at 10 r.p.m. and the temperature of the 
inlet air at 60.degree. C. When all of the solution had been applied, the 
drum was stopped and the tablets removed. There was thus obtained a 
mixture of highlighted tablets of excellent appearance. 
EXAMPLE 3 
(a)(i) Highlighting step 
24,400 410 mg. pink film coated intagliated placebo tablets were heated to 
60.degree. C. in a side-vented perforated drum coating machine (24 inch 
Accela-Cota). One liter of a 3.3% w/v aqueous solution of hydroxypropyl 
methylcellulose [`Pharmacoat` (Trade Mark) 606], containing 0.65% w/v 
polyethylene glycol 300 and light magnesium carbonate (30 g.) suspended 
therein, was applied continuously at 50 ml. min..sup.-1 by means of a low 
pressure air-spray unit. The drum speed was kept at 16 r.p.m. and the 
temperature of the inlet drying air at 60.degree. C. When all of the 
suspension had been applied, the drum was stopped and the tablets removed. 
There were thus obtained pink film coated tablets with intagliations 
highlighted in white. 
(a)(ii) Highlighting step 
37,000 270 mg. brown film coated intagliated placebo tablets were heated to 
60.degree. C. in a side-vented perforated drum coating machine (24 inch 
Accela-Cota). One liter of a 3.3% w/v aqueous solution of hydroxypropyl 
methylcellulose [`Pharmacoat` (Trade Mark) 606], containing 0.65% w/v 
polyethylene glycol 300, 0.1% w/v tartrazine water-soluble dye (Food, 
Drugs and Cosmetics Yellow No. 5), and light magnesium carbonate (30 g.) 
suspended therein, was applied continuously at 50 ml. min..sup.-1 by means 
of a low presure air-spray unit. The drum speed was kept at 16 r.p.m. and 
the temperature of the inlet drying air at 60.degree. C. When all of the 
suspension had been applied, the drum was stopped and the tablets removed. 
There were thus obtained brown film coated tablets with intagliations 
highlighted in yellow. 
(b) Solvent spray step 
5 kg. of the pink highlighted tablets, obtained as described in (a) (i) 
above, and 5 kg. of the brown highlighted tablets, obtained as described 
in (a) (ii) above, were placed in a side-vented perforated drum coating 
machine (24 inch Accela-Cota) and heated to 60.degree. C. 1:1 v/v 
methanol/methylene dichloride (2 l.) was applied continuously at 300 ml. 
min..sup.-1 by means of a high pressure airless spray unit. The drum speed 
was kept at 15 r.p.m. and the inlet air temperature at 60.degree. C. When 
all of the solvent had been applied, the drum was stopped and the tablets 
removed. There were thus obtained highlighted tablets of excellent 
appearance. 
EXAMPLE 4 
The solvent spray step described in Example 3 was repeated except that the 
2 l. of 1:1 v/v methanol/methylene dichloride were replaced by 1 l. of a 
0.5% w/v solution of polyethylene glycol 300 in 1:1 v/v methanol/methylene 
dichloride. There were thus obtained highlighted tablets of excellent 
appearance. 
EXAMPLE 5 
(a) Colour coating step 
50,000 200 mg. white intagliated medicinal tablets were heated to 
60.degree. C. in a side-vented perforated drum coating machine (24 inch 
Accela-Cota). 2.6 liters of a 9% w/v aqueous solution of hydroxypropyl 
methylcellulose [`Pharmacoat` (Trade Mark) 606], containing 1.4% w/v 
glycerol and pink pigment dispersion [175 g., `Opaspray` (Trade Mark) 
pink, Colorcon PLC, Orpington, Kent, England], were applied continuously 
at 50 ml. min..sup.-1 by means of a low pressure air-spray unit. The drum 
speed was kept at 12 r.p.m. and the temperature of the inlet drying air at 
60.degree. C. When all of the suspension had been applied, the drum was 
stopped and the tablets removed. There were thus obtained pink film coated 
intagliated tablets. 
(b) Highlighting step 
The pink film coated intagliated tablets were heated to 60.degree. C. in a 
side-vented perforated drum coating machine (24 inch Accela-Cota). 2 
liters of a 1.5% w/v suspension of light magnesium carbonate in 1:1 v/v 
methanol/methylene dichloride were applied continuously at 300 ml. 
min..sup.-1 by means of a high pressure airless spray unit. The drum speed 
was kept at 15 r.p.m. and the temperature of the inlet air at 60.degree. 
C. When all of the suspension had been applied, the drum was stopped and 
the tablets removed. There were thus obtained pink tablets having 
intagliations highlighted in white. 
(c) Solvent spray step 
The pink highlighted tablets were heated to 60.degree. C. in a side-vented 
perforated drum coating machine (24 inch Accela-Cota). 1:1 v/v 
methanol/methylene dichloride (1 l. ) was applied continuously at 300 ml. 
min..sup.-1 by means of a high pressure airless spray unit. The drum speed 
was kept at 15 r.p.m. and the inlet air temperature at 60.degree. C. When 
all of the solvent had been applied, the drum was stopped and the tablets 
removed. There were thus obtained highlighted tablets of satisfactory 
appearance. 
EXAMPLE 6 
(a) Highlighting step 
10 kg. of a mixture of coloured film coated intagliated placebo and 
medicinal tablets (weight range 100-640 mg.) were heated to 60.degree. C. 
in a side-vented perforated drum coating machine (24 inch Accela-Cota). 
One liter of a 5% w/v aqueous solution of hydroxypropyl methylcellulose 
[`Pharmacoat` (Trade Mark) 606], containing 1% w/v polyethylene glycol 300 
and light magnesium carbonate (30 g.) suspended therein, was applied 
continuously at 50 ml. min..sup.-1 by means of a low pressure air-spray 
unit. The drum speed was kept at 16 r.p.m. and the temperature of the 
inlet air at 60.degree. C. When all of the suspension had been applied, 
the drum was stopped and the tablets removed. There was thus obtained a 
mixture of coloured film coated tablets with intagliations highlighted in 
white. 
(b) Solvent spray step 
Approximately 400 coloured film coated tablets with intagliations 
highlighted in white, obtained as described in (a) above, were added to 
approximately 52,000 190 mg. white placebo tablets. The mixture of tablets 
was heated at 60.degree. C. in a side-vented perforated drum coating 
machine (24 inch Accela-Cota), and 500 ml. of a mixture of methanol and 
water (60:40 v/v) was applied continuously at 50 ml. min..sup.-1 using a 
low pressure air-spray unit. The drum speed was kept at 16 r.p.m. and the 
inlet air temperature at 60.degree. C. When all of the solvent had been 
applied, the drum was stopped and the tablets removed. There were thus 
obtained highlighted tablets of satisfactory appearance. 
EXAMPLE 7 
The highlighting step and solvent-spray step described in Example 6 were 
repeated, except that in the latter step the 500 ml. of 60:40 v/v 
methanol/water were replaced by 1 l. of 70:30 v/v methanol/acetone. There 
were thus obtained highlighted tablets of satisfactory appearance.