Over the past decades, the treatment of illness has been accomplished by administering drugs to the human body via various pharmaceutical dosage forms, like tablets. These traditional pharmaceutical products are still commonly seen today in the prescription and over-the-counter drug marketplace. Drug delivery is a growing field that represents one of the major research and development focus area of the pharmaceutical industry today. Chemical Engineers play an important and noteworthy role in this exciting field by applying their knowledge.
Drug products are usually composed of several components. They are as follows:
- Active Ingredients is what actually does the job you want the drug to do i.e. the therapeutic effect you want the medicine to achieve or the therapeutic action it claims to have. Active pharmaceutical ingredient (API), is the term used to refer to the biologically active component of a drug product (e.g. tablet, capsule). You should be able to easily identify the active ingredient on the package. For instance, a Nurofen tablet contains Ibuprofen which is the active ingredient
- Inactive Ingredients: It does not provide any therapeutic outcome you want the drug to achieve. Inactive ingredients are commonly known as “excipients”. Excipients are added to stabilize the active ingredient. It ensures that the active ingredient stays “active”, and, just as importantly, stable for a sufficiently long period of time.
In most cases, you won’t find the list of these ingredients on the package. They usually are industry secrets, thus not specified in medicine inserts. Thus the formulation of excipients in many cases is considered a trade secret (if not easily reverse-engineered).. As with new drug substances and dosage forms, novel excipients themselves can be patented.
Drug delivery refers to approaches, formulations, technologies, and systems for transporting a pharmaceutical compound in the body as needed to safely achieve its desired therapeutic effect.
Two main objectives to drug delivery:
- Drug targeting (to deliver a drug to the desired location in the body)
- Controlled release (to deliver a drug at the desired rate for a desired length of time).
The objective of drug targeting is accomplished by enteric-coating. It avoids dissolution of the tablet in the low pH of the stomach where it can cause irritation. It allows the tablet to pass through the stomach to the small intestine before dissolving. The coating dissolves in the more neutral environment of the intestine. The absorption of drugs in the small intestine is usually quite good due to the large surface area available.
Drug release: Oral intake is the most commonly used route of drug administration and the most convenient for patients resulting in high therapy compliance. The absorption of orally administered drugs is complex.
- HOW DO DRUGS GET INTO THE BODY?
- Unless injected directly into the bloodstream, drugs must be absorbed.
- WHAT IS DRUG ABSORPTION?
- The movement of drug molecules across biological barriers (mostly layers of cells) from the site of administration to the bloodstream.
- WHAT AFFECTS THE RATE OF DRUG ABSORPTION?
- Membrane permeability of the drug
- The surface area in contact with drug
- Blood flow to the site of absorption
- Destruction of the drug at or near the site of absorption
- WHAT DETERMINES RATE OF RELEASE OF DRUG FROM PHARMACEUTICAL PREPARATION?
- DOSAGE FORM
- Solutions: No Delay, Immediate Release
- Capsules & Tablets: Delay (Dissolution) Followed by Rapid Release
- Creams, Ointments & Suppositories: No Delay, but Slow Release
- ADDITIVES (EXCIPIENTS)
- Decrease Rate of Dissolution
- Coating Agents
- Increase Rate of Dissolution
- Variable Effects on Rate of Dissolution
- Colouring Agents
- Flavoring Agents
- Decrease Rate of Dissolution
- MANUFACTURING PARAMETERS
- Tablet Compression – Hard tablets dissolve more slowly
- Tablet Shape – Round tablets dissolve more slowly
- Tablet Size – Large tablets dissolve more slowly
- DELAYED RELEASE PREPARATIONS
- Enteric Coating – Dissolve in intestines, not stomach
- DOSAGE FORM
Chemical engineers working in the pharmaceuticals industry are crucial in making the drugs we rely on every day. They also play a vital role in scaling-up the production of new medicines to fight devastating diseases.
Having a strong background in multiple disciplines with competencies in rate and equilibrium processes, heat and mass transport, reaction rate analysis, mixing/fluid dynamics, separation processes, scale-up phenomena, safety analysis and reactor/equipment design, the primary role of the chemical engineer is therefore to use these capabilities to help in the growth of drug industry that drives us towards a healthier and safer future.