What are inactive ingredients?
Generally less than 10% of a medicine is the active ingredient and the remainder are the inactive ingredients.
(All processed food has inactive ingredients. These are called additives.)
Why are inactive ingredients used in medicines?
Inactive ingredients are used to take the active ingredient to a site in the body where it will be most effective.
Specialised inactive ingredients such as film coatings, binders, disintegrants and solubilisers are used for tablets and capsules to control how, where, and when the medicine is released in the body to achieve maximum benefit. Long acting and slow realease tablets and capsules have simplified the daily routine of taking a number of medicines at fequent intervals.
The active ingredient in tablets and capsules is usually very small (5 to 20 mg) and must be bulked up to a size that is easy for patients to handle.
Commonly used filling agents include Lactose and Cellulose powder.
Other inactive ingredients such as anti-oxidants, preservatives and acidity regulators prevent medicines deteriorating.
Inactive ingredients such as emulsifiers, wetting agents and thickeners are used to make creams, ointments and lotions. These generally contain less than 1% of active ingredient.
Other inactive ingredients such as lubricants and fillers are used to help with the making of tablets and capsules to ensure the ingredients flow smoothly through the machinery that manufactures them.
Transdermal (through the skin) medicines release the medicine from a patch applied to the skin. A good example is the nicotine patach used to help people stop smoking. They have a new range of inactive ingredients called transdermal agents such as adhesives and plastic films. They also have inactive ingredients called “solubilisers” that help carry the medicine through the skin into the blood stream.
Why are inactive ingredients often used for more than one purpose?
Flour is used in cooking for all sorts of purposes – lots of flour for baking and just a little for gravy. So it is with inactive ingredients, some are used for many different purposes as our category list shows. It all depends on how, where and why the inactive ingredient is used.
For example, an inactive ingredient may have emulsifying, thickening and suspending properties depending on how it is used and what medicine it is used for. The category descriptions we use are brief and general in nature and not intended to be detailed descriptions.
Who controls the quality of inactive ingredients?
The safety and approval of inactive ingredients is controlled by a number of governmental agencies such as the US Food and Drug Administration (FDA) Center for Drug Evaluation and Research.
The European Union legislation uses the prefix E on approved inactive ingredients, eg E460 for cellulose. If an inactive ingredient has no E number it does not mean it is not suitable for use.
Where do we obtain our information from?
Our medicine information mainly comes from the medicine manufacturers’ technical information sheets, which we get from the Ministry of Health through Medsafe.
In addition we maintain a library of current pharmaceutical reference books and CDs such as Martindale, Stockleys, APH, Handbook of Pharmaceutical Excipients, BNF. We also regularly access selected websites of government or not-for-profit organisations.