When a baker prepares chocolate chip cookies, the main component of the cookies arguably are the chocolate chips. But, many other ingredients are needed to create the cookies – butter, eggs, flour, sugar, etc.
In tablets and capsules, there’s a similar trend. There is an active ingredient, similar to chocolate chips found in chocolate chip cookies. The active ingredient refers to the part of the tablet or capsule that elicits pharmacologic activity. But, it would be impossible to form a pill without other ingredients also incorporated. These other inactive ingredients make it possible to form a pill and make it chemically stable. Inactive ingredients in medications are called excipients.
Pharmacists are commonly asked about excipients contained within various medications. Patients taking a medication may be curious about its excipients.
Excipients may vary from manufacturer to manufacturer for a certain medication. For example, the generic medication amlodipine besylate is produced by various generic manufacturers: Apotex, Cipla, Hebei Changshan, Lupin, Mylan, Strides Pharma, Watson Labs, etc. All of these manufacturers have the same chemical component of amlodipine besylate contained as the active ingredient in their tablets, but each manufacturer may have slightly different excipients within their tablets otherwise. Albeit being much more regulated for uniformity, this is similar to how different chocolate chip cookies can have slightly different recipes.
As excipients can vary from medicine to medicine and from manufacturer to manufacturer, some individuals are curious about excipients themselves. Some individuals may have an allergy or dietary restrictions related to certain excipients found in one medication, but not another. Some individuals may think that a certain manufacturer of a medication is more effective than another manufacturer even though the FDA views them to be equivalent products. Other individuals who analyze ingredients in various products may simply be curious about the role each excipient plays within the tablet or capsule.
Listed below are common excipient categories, examples of ingredients within each category, and what they are used for. Various ingredients can serve multiple roles, and that is reflected in the list below.
This discussion focuses specifically on tablets and capsules. Other excipients can be present for oral liquids, IV medications, creams, ointments, and gels. This list is not all inclusive.
Binders
Binders can also be referred to as adhesives or granulating agents. Binders help all of the ingredients within a tablet, both active and inactive, stick together to form a viable pill and help it to remain stable over time. Binders also allow the active ingredient(s) within a medicine to release once ingested. This can be done with or without a disintegrant (discussed below).
Examples:
- Gum acacia
- Hydroxypropyl methylcellulose (HPMC)
- Polyethylene glycol (PEG)
- Povidone
- Starch paste
- Sucrose syrup, liquid glucose (caution in diabetes)
Coating
Coating layers, be it sugar-coating or film-coating, on the exterior portion of tablets and capsules prevent tablet/capsule degradation due to a number of possible environmental factors. These factors are most commonly light, oxygen, and moisture. Coatings can also be used to mask unpleasant tastes.
Coatings can also be used to alter the timing of release, or medication activation, in the body. For example, if a physician wanted a medication to wait until arriving in the duodenum (small intestine) to begin working, an enteric-coated tablet could make this possible. An enteric-coated tablet primarily protects the core of the medicine against stomach acid. Without an enteric coating, a medication taken orally may begin to activate in the stomach.
FAST FACT: if a medication has a suffix of “DR” or “EC”, it has an enteric coating. For example: aspirin EC, naproxen EC, omeprazole DR.
Examples:
- Cellulose acetate phthalate
- Gelatin (commonly pig-derived; should be avoided in anybody who wishes to avoid pork)
- Gluten (should be used in caution for patients with celiac disease)
- Gum acacia
- Hydroxypropyl methylcellulose (HPMC)
- Polyethylene glycol (PEG)
- Povidone
- Shellac
- Sucrose (caution in diabetes)
- Talc
- Titanium dioxide
Diluents & Fillers
Diluents and fillers add size and volume to tablets and capsules to make them viable dosage forms. By themselves, active ingredients in many medications would be far too small to administer and dispense as a single component. By adding diluents and fillers, medications became possible to physically hold and work with.
Examples:
- Bentonite
- Calcium salts
- Cellulose products (various)
- Corn starches, rice staches, wheat starches, etc (wheat-based starches should be avoided in individuals with celiac disease)
- Gelatin (commonly pig-derived; should be avoided in anybody who wishes to avoid pork)
- Lactose (should be used in caution in patients that are lactose intolerant)
- Mannitol (should be used in caution in patients with intracranial hypertension)
- Sorbitol (should be used in caution in patients with irritable bowel syndrome)
Disintegrants
After a tablet or capsule is swallowed, the body begins to digest the medication to allow it to exert its intended effect while concurrently breaking it down to excrete it out of the body. Disintegrants are ingredients within medications that help to control this release rate as a medication works its way and dissolves through the gastrointestinal tract.
Some medications work by becoming active in a certain part of the body, and disintegrants help to control the release rate. This is a similar phenomenon to enteric-coated tablets and capsules, discussed above. For example, if a medication has an intended pharmacologic effect on a person’s large intestine, then the disintegrant would be one of the factors that would help to allow the medication to optimally become active within the large intestine specifically.
Examples:
- AC-Di-Sol
- Alginic acid
- Amberlite
- Cellulose products (various)
- Compressible sugar
- Corn starches, rice starches, wheat starches (wheat-based starches should be avoided in individuals with celiac disease)
- Explotab
- Gelatin (commonly pig-derived; should be avoided in anybody who wishes to avoid pork)
- Polacrilin potassium
Flavoring, Sweetening, and Coloring Agents
Medicines that dissolve in the mouth typically contain flavoring agents and/or sweetening agents. Occasionally, other oral medications may also incorporate these agents to improve palatability if the medicine has a poor taste. Additionally, medications may contain coloring agents for aesthetic purposes.
Coloring Agent Examples:
- Caramel
- D&C Red No. 3
- Ferric oxide
- Magnesium carbonate
- Yellow No.6
Flavoring/Sweetener Examples:
- Aspartame (sugar-free)
- Dextrose
- Glycerin
- Lactose (should be used in caution for patients that are lactose intolerant)
- Maltitol
- Mannitol
- Monk fruit extract
- Phenylalanine (should be used in caution in patients with phenylketonuria)
- Saccharin (sugar-free)
- Sorbitol (should be used in caution for patients with irritable bowel syndrome)
- Stevia
- Sucrose (caution in diabetes)
- Xylitol (should not be ingested by dogs)
Lubricants
Lubricants are primarily used for the tablet and capsule creation process. Lubricants help keep ingredients from sticking to each other and to equipment during the manufacturing process.
Examples:
- Calcium
- Glycerin
- Magnesium stearate
- Mineral oil
- Polyethylene glycol (PEG)
- Talc
Example – Metformin 500 mg tablets: see below.
Metformin 500 mg tablets (Ascend Laboratories, LLC). Corresponding NDC codes: 67877-0561-01, 67877-0561-05, 67877-0561-10, 67877-0562-01. This is a medication commonly used to control blood sugar levels in individuals with type 2 diabetes mellitus.
The active ingredient contained in this medication is metformin hydrochloride. The tablets also contain the following inactive ingredients:
- Blackberry – flavoring agent
- Corn starch – binder, filler
- Hydroxypropyl methylcellulose 2910 – binder
- Magnesium stearate – lubricant
- Maltodextrin – filler
- Polyethylene glycol – binder/lubricant
- Povidone K30 – granulating agent
- Povidone K90 – granulating agent
- Triacetin – humectant/plasticizer
References:
- Drugs@FDA: FDA-Approved Drugs. United States Food & Drug Administration. Accessed 10 May 2020.
- Tablet Binders. LFA Machines Oxford LTD. Accessed 10 May 2020.
- Understanding Tablet Coating Process. LFA Machines Oxford LTD. Accessed 11 May 2020.
- Diluent Excipients. American Pharmaceutical Review. Accessed 11 May 2020.
- An Overview of Disintegrants. LFA Machines Oxford LTD. Accessed 11 May 2020.
- Pharmaceutical Flavoring Agents. Spectrum Chemical Manufacturing Corp. Accessed 11 May 2020.
- Pharmaceutical Sweetening Agents. Spectrum Chemical Manufacturing Corp. Accessed 11 May 2020.
- Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices. United States Food & Drug Administration. Accessed 11 May 2020.
- Lubricants for Solid Oral Dosage Forms. BASF SE. Accessed 11 May 2020.
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