Why are prescription drugs mostly white in colour?

[cool_walking_]

Am I imagining it?
Is there something in common about the structure of substances that interact with human biology which means they tend to be white?
Do medication manufacturers just somehow artificially whiten them to meet consumer expectations?

Thanks for any input.

 

[Drakkith]

I'm guessing that the "filler" they put in pills is where most of the color is coming from and has little to do with the drug's color in most cases.

 

[DrStupid]

Is there something in common about the structure of substances that interact with human biology which means they tend to be white?

There actually are active ingredients which are not white (e.g. dithranol). I don't expect that the percentage of white drug substances significantly differs from the expectancy value for all organic compounds. But I don't have the data to check it.

Do medication manufacturers just somehow artificially whiten them to meet consumer expectations?

No, they artifically pigment them in order to prevent confusions between different drugs with similar shape. Tablets without colourants have the colour of filler or coating which are usually white (e.g. lactose).

 

[Vanadium 50]

There actually are active ingredients which are not white (e.g. dithranol).

Or calamine (an inorganic).

 

[Greg Bernhardt]

I wonder if there is an element of not wanting the pills to look like candy to children?

 

[Borek]

Some pills are blue.

 

[hilbert2]

Usually when an organic compound has a color other than white, it has a long conjugated chain (like in beta-carotene or similar) that makes it absorb visible light at some typical wavelength range.

 

[jim mcnamara]

The fillers and coatings answer is most of it. Vitamins and some other nutrients have color, but they are usually in such small abundance in a pill as to not add much color. (Except the horse pill sized supplements that contain everything remotely like a human micronutrient. ) Many pharmaceuticals are whitish anyway. We are assuming they are powders or crystals - for the example below.

Suppose you take, um, 20mg of spironolactone - a diuretic. It has density approximately equal to table sugar. So, get yourself a magnifying glass and some tweezers (forceps). Count out 10 grains of granulated sugar. Put them in a neat pile. Can you even see it from 2 meters away? If you dropped a pill that small would you ever find it? Try getting just a single one of those "nanopills" out of a bottle.

There are good reasons for fillers - you can see the most obvious ones already. Us. People who take the pills. Coatings and shapes identify pills to consumers of those pills. 'I have to take two pink ones, a blue one, and the white long skiny one'

Fillers and coatings can affect absorption of the drug, timing it to release slowly, or release in the intestine, or withstand stomach acid. Not mention help fumble fingered people with decent sized pills. All this from pills almost completely made of fillers and coatings.

Pills also have small mnemonics in/on the surface so Pharmacists can identify them. The formulaies they have come with nifty pill pictures. To decode the pill. Try that with a nanopill.

 

[hilbert2]

I think the OP is asking why the actual active ingredients in medications (like acetylsalicylic acid, bisoprolol, zuclopenthixol, etc...) are usually white solids. The reason is that the electronic energy levels of organic molecules usually have such spacings that they don't preferentially absorb visible light of some particular color.

 

[marjudo]

It can be only for commercial reason. Or because it's a neutral color. Maybe some people would not eat green grugs.

 

[Comeback City]

It can be only for commercial reason. Or because it's a neutral color. Maybe some people would not eat green grugs.

Interesting thought, but why would they specifically make them white by that logic?

 

[DrClaude]

It can be only for commercial reason.

Only?

Maybe some people would not eat green grugs.

But there are green pills.

 

[Borek]

How are you going to take the white one, when the choice is between blue and red?

 

[berkeman]

Some pills are blue.

I've never seen such a thing. Do you have a peer-reviewed reference for that?

 

[DrClaude]

I've never seen such a thing. Do you have a peer-reviewed reference for that?

I can show you a few commercials

 

[Comeback City]

How are you going to take the white one, when the choice is between blue and red?

Ah, the dreaded 2-party system has made its way into chemistry

 

[cool_walking_]

Hey everyone. Easily distracted OP here. hilbert2 gets me.

the electronic energy levels of organic molecules usually have such spacings that they don't preferentially absorb visible light of some particular color.

I'm only a layman physicist. How does this work? What spacings, and what is it about these spacings that makes light do it's colourful thing?

 

[HAYAO]

Hey everyone. Easily distracted OP here. hilbert2 gets me.

I'm only a layman physicist. How does this work? What spacings, and what is it about these spacings that makes light do it's colourful thing?

A photon has energy. For example, green light corresponds to each of the photon having energy of 2.3 eV. If an organic compound do not have any excited state energy level of this energy, then the compound will not absorb this light and the light just passes through.

Visible photon is somewhere around 1.8 eV to 3.1 eV.

 

[Borek]

To add to what HAYAO said: photon can get absorbed when its energy is that required to move an electron from one allowed energy level (orbital) to another (we call the lower energy state a basic one, and the higher energy level state the excited one).

Google for Bohr atom and Rydberg formula - while as of today we have much better ways of describing electrons and atoms/molecules (IOW: an older theory has been superseded by a new theory, nice example of how the science works) they still give a nice and rather easy to follow explanation of how the spectra works. Just remember to treat them more in terms of an analogy than in terms of the real thing.

 

[HAYAO]

To add to what HAYAO said: photon can get absorbed when its energy is that required to move an electron from one allowed energy level (orbital) to another (we call the lower energy state a basic one, and the higher energy level state the excited one).

I always call it the "ground state" though. I didn't know you can call it the "base state". But I guess talking about terminology is trivial.

 

[Borek]

I always call it the "ground state" though. I didn't know you can call it the "base state". But I guess talking about terminology is trivial.

Chances you are right and I just incorrectly translated from Polish.

 

[HAYAO]

Chances you are right and I just incorrectly translated from Polish.

I see. Now that you've mentioned it, translation from Japanese to English also leads to "basic state". Interesting.