Active pharmaceutical ingredient

What is an API or Active Pharmaceutical Ingredient?

An active pharmaceutical ingredient popularly known as API is the biologically active drug product component. API is a raw material and, also known as bulk drugs.

As we know, pharmaceutical products, like a tablet or capsule, are usually composed of several ingredients. So, API is the primary ingredient. Other ingredients are commonly known as “excipients.” Excipients are generally defined as any ingredient in medicine other than the active ingredient.

Pharmaceutical formulation is a mixture of APIs and excipients. 

So, let us say, Ascoril cough syrup is a formulation, which contains terbutaline sulfate as an API and other ingredients, e.g., sorbitol as an excipient.

Active pharmaceutical ingredient: Examples 

WHO defines “active pharmaceutical ingredient (API) as 

  • A substance intended to furnish pharmacological activity.
  • Or A substance to have a direct effect on the diagnosis, mitigation, treatment, cure, or prevention of disease.
  • or A substance to have direct effect in correcting restoring, or modifying physiological functions in human beings.” 

Examples of API:

  • Vildagliptin and sitagliptin- anti-diabetic agents.
  • Tacrolimus, Sirolimus- Immunosuppressants.
  • Atorvastatin, Rosuvastatin- Cardiology.

Commonly used excipients:

The excipient is an inactive constituent. It is a substance without therapeutic properties or power. Excipients are used to guarantee the physicochemical and organoleptic properties, the stability of pharmaceutical products. Commonly used excipients are: 

  • Preservatives– Methylparaben and propylparaben.
  • Sweeteners– helps to improve the taste, e.g., Liquid Glucose, Sucrose, Saccharin Sodium, Sorbitol, Ammonium glycyrrhizate.
  • Thickeners- helps to prepare thick viscous syrups, e.g., Xanthan gum, Acacia, Propylene glycol.
  • Flavors– helps masking of a bitter taste, e.g., Menthol, Caramel, Raspberry flavor, Peppermint oil, Blackcurrant flavor, and Strawberry flavor.
  • Coloring agents– helps to prolong the shelf life of the medicine. e.g., benzoic acid derivatives, such as sodium benzoate.
  • Buffers– maintain an optimal pH and solubility of active ingredients and other excipients. e.g., citric acid.

Types of Active Pharmaceutical Ingredient/s

The nature of the APIs could be chemical synthetic drugs or natural chemical drugs.

Chemical synthetic drugs

Chemical synthetic drugs are further divided into inorganic synthetic drugs and organic synthetic drugs.


  • inorganic synthetic drugs: Aluminum hydroxide and magnesium trisilicate.
  • Organic synthetic drugs like- Aspirin, chloramphenicol, caffeine.

Natural chemical drugs

As the name suggests, natural chemical drugs are mainly derived from nature, which can be divided into biochemical drugs and phytochemical drugs.

  • Biochemical drugs: are the drugs obtained through biological processing—antibiotics like Amoxycillin, cloxacillin. 
  • Phytochemicals are active pharmaceutical ingredients that exist naturally in plants. Example- Paclitaxel (an anticancer drug).

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