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Understanding APIs, Intermediates, and Finished Dosage Forms: A Guide for Pharma Professionals


In the intricate landscape of pharmaceutical development and manufacturing, a fundamental understanding of Active Pharmaceutical Ingredients (APIs), intermediates, and finished dosage forms is paramount for professionals in the field.

Each stage is crucial in ensuring efficacy, safety, and regulatory compliance, from the inception of a drug’s synthesis to its final formulation.

This guide aims to provide pharmaceutical professionals with a comprehensive overview of APIs, intermediates, and finished dosage forms, delving into their intricacies, and regulatory considerations within the pharmaceutical industry.

Active Pharmaceutical Ingredients (APIs)

APIs constitute the central ingredient of any drug formulation, providing pharmacological activity or other direct effects in disease treatment, prevention, or diagnosis. They are manufactured through chemical synthesis, fermentation, recombinant DNA technology, or isolation from natural sources.

Processes of API Manufacture

API Process Development and Production involves several processing stages, such as reaction, crystallisation, separation, purification, filter cake washing, solvent swapping, and solvent exchange.

API Process Development Stage: Following drug discovery and early formulation, scientists determine how to convert the Active Pharmaceutical Ingredient (API) into an appropriate dose form for pilot production. Methods devised during this stage are later scaled up for commercial manufacturing pending successful clinical studies.

Selection of Pharmaceutical Manufacturing Machinery: The choice of machinery for blending, extrusion, drying, milling, and micronization is critical. This selection significantly influences the final drug product’s physical characteristics and quality features.

Powder Processing and Particle Size Distribution (PSD): Powder processing involves milling, which reduces particle size for optimal processability, bioavailability, reactivity, and safety. Achieving the suitable particle size distribution (PSD) ensures drug efficacy and delivery to targeted body sites.

API Manufacturers

API production is a complex process involving chemical synthesis or biochemical methods. According to the FDA, Indian and Chinese companies dominate the API manufacturing sector. Pharmaceutical companies usually adhere to their country’s safety standards when manufacturing the final product.

Regulatory Compliance and Safety

The safety and efficacy of drug products hinge on the quality of their active ingredients, ensured through optimised processes.

Poor API process development and production, along with contaminated active ingredients, are linked to adverse health effects, including fatalities. Thus, regulatory procedures for approving active ingredients are being strengthened globally.

This regulation bolsters the pharmaceutical supply chain, enhancing medication quality and safety. APIs undergo independent pre-qualification processes, ensuring adherence to WHO Good Manufacturing Practices (GMP) and streamlining FPP pre-qualification.

API Intermediates

Pharmaceutical intermediates are chemical compounds synthesised and used to produce active pharmaceutical ingredients (APIs). They are formed at various stages in API synthesis and facilitate API synthesis by serving as building blocks or precursor molecules. They undergo chemical modifications to create the desired API.

Role of Intermediates in API Synthesis

Intermediates play a vital role in API synthesis by enabling controlled modifications for desired chemical properties. They represent various stages in the synthesis pathway toward the API, contributing significantly to the efficiency, scalability, and quality of the synthesis process. Well-designed intermediates can simplify complex routes, enhance yield, and reduce costs.

For example, a common intermediate in API synthesis is [benzene], which can be modified to produce a wide range of APIs. This versatility is one of the reasons why intermediates are so important in API synthesis.

Examples of Pharmaceutical Intermediates

  • Key Intermediates: Central to API synthesis, these intermediates undergo multiple transformations to form the desired API structure.
  • Protecting Group Intermediates: Involving temporary modifications of functional groups in the API molecule, protecting groups prevents undesired reactions.
  • Salt Formation Intermediates: APIs are sometimes produced as salts to enhance stability and solubility.
  • Chiral Intermediates: Introduce handedness into APIs, enabling the production of specific forms.

Regulatory Consideration:

Pharmaceutical intermediates are subject to GMP guidelines for quality control, compelling manufacturers to establish appropriate systems and processes. To ensure safety and quality, they must identify and control synthesis-related impurities as regulatory authorities require.

Process validation is necessary to maintain consistent quality in manufacturing, with manufacturers obliged to demonstrate process capability to meet specified standards. Additionally, comprehensive documentation is vital for traceability and regulatory assessment, ensuring integrity and compliance throughout the pharmaceutical intermediate manufacturing process.

Finished Dosage Forms (FDFs) 

A finished dosage form (FDF) represents the consumable, finalised drug product. It encompasses tablets, pills, liquid solutions, and other forms of FDFs. All FDFs contain an API along with other inactive components.

Different types of FDF

There are various types of finished dosage forms, each with unique properties and applications:

  1. Tablets: Tablets are solid dosage forms containing API and excipients. They come in multiple shapes, sizes, and colours, and can be designed for immediate release, extended release, or enteric coating.
  2. Capsules: Capsules are solid dosage forms encapsulating API and excipients in gelatin shells. They come in two main varieties: hard capsules (powder, granules, or pellets) and soft capsules (liquid or semi-solid fill).
  3. Liquids: Liquid dosage includes solutions, suspensions, and syrups. These are commonly used for paediatric and geriatric patients and individuals who have difficulty swallowing solid dosage forms.
  4. Ointments: Ointments are semi-solid dosage forms often used for topical application. They are typically a combination of an API and a base and are used for dermatological, respiratory, and ophthalmic purposes.
  5. Inhalants: Inhalants are intended to be inhaled into the lungs. They can be metered-dose inhalers, dry powder inhalers, or nebulized solutions and are often used for respiratory conditions such as asthma and Chronic Obstructive Pulmonary Disease (COPD).

Regulatory Oversight

The FDA mandates manufacturers to demonstrate the efficacy of medications through laboratory settings and clinical trials involving actual patients. Stricter criteria and inspections have been implemented to regulate medications produced outside the home countries of pharmaceutical corporations.


Understanding APIs, intermediates, and finished dosage forms is pivotal for pharmaceutical professionals. The production of APIs encompasses rigorous processes, impacting the efficacy and safety of drug products from development to manufacturing.

Regulatory compliance ensures quality and safety, with intermediates playing a vital role in API synthesis. Diverse finished dosage forms cater to various patient needs. They are regulated to ensure efficacy and safety. Strengthening regulatory oversight is crucial for maintaining medication quality and safety and safeguarding public health globally.

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