Active Ingredient in a Medication Function

An active ingredient is the component of a medication that's responsible for its effects. In addition to providing a therapeutic benefit, an active ingredient can also cause adverse or unintended effects that could cause mild discomfort, or worse.

When medication is prescribed for you, the beneficial effects should outweigh the adverse effects. Furthermore, adverse effects should be tolerable. If the active ingredients in any medication cause substantial or intolerable side effects for you, then the drug is usually discontinued.

According to the FDA, an active ingredient is any component that provides a pharmacological activity or other direct effects in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body of man or animals.

Active ingredients are also known as therapeutically active ingredients or pharmaceutically active ingredients. In addition to active ingredients, most medications also contain inactive ingredients, such as colors, binders, and preservatives.

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Example of Active Ingredient: Sertraline Hydrochloride

The active ingredient in Zoloft (sertraline), a prescription medication used to treat depression, is sertraline hydrochloride. Sertraline hydrochloride is slightly soluble in water. Sertraline inhibits the uptake and deactivation of the body's naturally produced serotonin, a mood regulator, in the brain. Sertraline has little effect on other neurotransmitters, such as dopamine and norepinephrine.

Adverse effects of sertraline can include the following:

  • Dizziness
  • Skin rash
  • Nervousness
  • Insomnia
  • Nausea
  • Diarrhea
  • Constipation
  • Upset stomach
  • Headache
  • Stomach pain
  • Changes in appetite
  • Sexual dysfunction
  • Dry mouth
  • Weight loss

Zoloft is a selective serotonin reuptake inhibitor (SSRI) used to treat major depressive disorder (MDD), obsessive-compulsive disorder, panic disorder, PTSD, premenstrual dysmorphic disorder, and social anxiety disorder.

Sometimes, if you take more than one medication, the active ingredients of two or more of the medications that you take can interact in dangerous ways.

For example, when Zoloft is taken with the monoamine oxidase inhibitors (MAOIs), another type of antidepressant, serious drug interactions can occur. Serotonin syndrome, characterized by muscle rigidity, myoclonus, hyperthermia, changes in vital signs, irritability, extreme agitation, delirium, and coma can occur.

Other Examples of Active Ingredients

The active ingredient in Prilosec (omeprazole), an over-the-counter medication used to treat gastroesophageal reflux disease (GERD), gastric ulcers, or heartburn, is omeprazole magnesium. The most common side effects of Prilosec include stomach pain, gas, nausea, vomiting, diarrhea, and headache.

The active ingredient in BJ's Allergy Medicine, an over-the-counter medication used to treat nasal allergies and hay fever, is diphenhydramine HCL, which is also sold under the brand name Benadryl. Some of the common side effects include drowsiness, dizziness, constipation, stomach upset, blurred vision, dry mouth/nose/throat.

If you have any questions about your medications, your pharmacist can help you learn how to use your prescription and over-the-counter medicines safely and effectively.

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  1. US Food and Drug Administration. Drugs@FDA glossary of terms. November 4, 2017

Additional Reading
  • Burstein A, Talmi A, Stafford B, Kelsay K. Child & Adolescent Psychiatric Disorders & Psychosocial Aspects of Pediatrics. In: Hay WW, Jr., Levin MJ, Deterding RR, Abzug MJ. eds. CURRENT Diagnosis & Treatment: Pediatrics, 22e. New York, NY: McGraw-Hill; 2013. 
  • Satterfield JM, Feldman MD. Anxiety. In: Feldman MD, Christensen JF, Satterfield JM. eds. Behavioral Medicine: A Guide for Clinical Practice, 4e. New York, NY: McGraw-Hill; 2014.
  • Selected Sources