When Donna was first diagnosed with blood clots in her lungs 20 years ago, she took a common blood thinner for over 10 years with no problems. Then her doctor told her that she could stop taking it, so she did. Five years later, Donna was back in the Emergency Department with trouble breathing. This time, she again had blood clots, but in both her lungs.
She spent 2 days in the hospital, where her doctors restarted her previous blood thinner. She was discharged to home, where her breathing gradually improved, but she started feeling “itchy all over." After trying several over-the-counter allergy medications with little success, she saw her doctor, who prescribed other allergy medicines, which didn’t give her any relief.
Finally, although she had taken the same drug for years without any problems, her doctor changed her blood thinner medication.
And to everyone’s surprise, her itching stopped.
Did she develop an allergy to her old blood thinner medicine? Possibly, but other compounds besides a pill’s active ingredients can cause side effects or change how you absorb a particular medication.
These “inactive” ingredients are called excipients. They lurk in our tablets, capsules, and liquid medicines. Many generic drugs use different excipients than the original branded formulation.
Generic drugs are only required to include the same active ingredient. Generic medications often have different colors, coatings, sizes, and shapes, including other "inactive" compounds than the original, branded medicine. This can lead to differences in how the original medicine acts in your body compared to its generic counterparts.
Tablets and capsules must contain a specific amount of a drug’s active ingredient. This is often just a tiny amount of powder. To make it pill-sized and shaped, other compounds called excipients are added. These “extra ingredients” may help preserve it, color it, sweeten it, speed its dissolving under your tongue, or make it easier to manufacture.
Stabilizers or preservatives protect the final product from contamination by microbes or slow down the degradation of the active ingredient when exposed to oxygen and moisture.
Sodium bisulfite is a standard stabilizer that helps an active ingredient stay potent longer. Some commonly used preservatives include sodium benzoate, sorbic acid, and parabens like methylparaben, ethylparaben, propylparaben, and butylparaben.
With most medicines, combining the active ingredient, diluent, and dye or coloring agent doesn’t provide enough powder to fill out each dose and create tablets big enough to pick up, handle, and swallow. A filler agent like cornstarch, lactose, sucrose, dextrose, or talc is often added to the mixture, adding bulk. This helps create a tablet or capsule of a specific size.
A diluent is often added to help blend the active ingredients evenly throughout the mixture, giving the final tablets or caplets a more consistent color. It also helps ensure an equivalent dose in each piece when a tablet is cut or broken in half.
Although your pill mixture contains active ingredient, diluent, food coloring, and filler, you often need to add a binder and lubricant in order to make the pill easier to manufacture when using automated pill presses.
Dry, powdery snow is fun to ski in but worthless for a good snowball fight. Water helps snow stick together when compressed into a snowball. Similarly, a binder gives powdered medicine the “stickiness” it needs to form a tablet when pressed into a particular shape.
When making waffles, the batter is poured onto the bottom of a hot waffle iron, which is then closed to cook. When the cooking time is up, you open the iron and lift the steaming waffle off the hot griddle and onto a waiting plate.
It's aggravating when your awaited treat refuses to come loose, instead ripping itself apart. You end up peeling waffle off each side of your waffle iron. When a medicine tablet is pressed into its final shape, it also has to be able to LET GO and roll away, which is why a lubricant is often added to the medicated mixture, like oil is added to a waffle iron.
Another inactive ingredient is a wetting agent or “disintegrant”. It pulls water into a tablet more quickly, speeding up the process of dissolving it and releasing the active ingredient more rapidly and completely.
Chewable tablets are often sweetened and flavored, while preservatives are added to liquid medicines like ear drops, eye drops, and nose sprays to discourage the growth of microbes.
The active drug is not always to blame for problems. Generics often use different inactive ingredients, which can trigger side effects like allergic reactions.
Dr. Louise Achey, Doctor of Pharmacy, is a 43-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog, TheMedicationInsider.com.
Ó2023 Louise Achey
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