This article was taken from the September 2011 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
Each month Wired's chemist Dr John Emsley deconstructs an everyday product. He is author of 110 research papers and ten books, including his most recent:A Healthy, Wealthy, Sustainable World (Royal Society of Chemistry).
INGREDIENTS
•Anhydrous dibasic calcium phosphate
•Sildenafil citrate
•Microcrystalline cellulose
•Croscarmellose sodium
•Magnesium stearate
•Lactose
•Triacetin
•Hypromellose
•Titanium dioxide
•FD&C Blue aluminium lake
ANHYDROUS DIBASIC CALCIUM PHOSPHATE
E341 is there to bulk out the tablet. This salt is used as an acidity regulator in baking powders and added to the flour for making noodles.
SILDENAFIL CITRATE
The release of nitric oxide molecules causes penile erection.
Sildenafil controls the enzyme that restricts blood flow to the penis, causing the same effect.
MICROCRYSTALLINE CELLULOSE
A form of cellulose extracted from wood pulp, this acts as an excipient, meaning it is not an active ingredient but it is there to help the tablet disintegrate in the stomach.
CCROSCARMELLOSE SODIUM
This is another form of cellulose, but its chains are cross-linked and this too is an excipient, in this case causing the tablet to swell when it becomes moist.
MAGNESIUM STEARATE
Mg(C18H35O2)2 is added to the mixture of ingredients as a lubricant so that when these are stamped into tablets they don't stick tto the machinery.
LACTOSE
Also known as C12H22O11, lactose is another tablet-bulking agent. It consists of two simple sugars, glucose and galactose, bonded together.
HYPROMELLOSE
E464 is a very sticky liquid which finds use in tile adhesive.
Here it acts partly as a glue and partly as a controlled release agent for the sildenafil so that its effects last longer.
TRIACETIN
This prevents the tablet from drying out and becoming powdery.
It was once used to treat fungal skin infections, and is used in cigarette filters to keep the fibres soft.
TITANIUM DIOXIDE
TiO2 is a bright white pigment found in paints and in the confectioner's icing used on wedding cakes. Here it dilutes the blue dye used to colour the tablet to create a paler shade.
FD&C BLUE ALUMINIUM LAKE
This consists of dye molecules bonded to a metal atom, the object being to make the dye insoluble so it will pass through the gut without being absorbed.
This article was originally published by WIRED UK
