Drug Formulation and Delivery Method

Drug formulation is the multistep process where the active pharmaceutical ingredients (APIs) are mixed with all other components and become the final beneficial medicinal product. The factors such as particle size, polymorphism, pH, and solubility of the active drug need to be considered. After drug formulation, they will be administered at a therapeutic concentration to a particular site of action for a specified period. Drugs can be taken in a variety of ways, including intravenous injection, inhalation, swallowing, and absorption through the skin. Each one has its advantages and disadvantages, and different drug formulation to choose suitable and efficient delivery methods.

Fig.1 The interdependence of physicochemical properties, formulation, and drug delivery (Barich, 2016)

Drug Properties

The physicochemical properties of the drug play a critical role in drug formulation and delivery. The goal in drug delivery is to bring the drug concentration to a specific level and maintain it at that level for a specific duration of time. Generally, a new drug must be both sufficiently soluble and chemically stable in solution. Therefore, stability and solubility are two key physicochemical properties during the drug formulation design. Solubility is affected by many factors, such as the pH of the solution, the drug’s temperature, the hydrophobic/ hydrophilic nature of the drug, solid form of the drug, buffer concentration/composition, ionic strength, and the presence of complexing agents in solution. There are two types of drug stability, namely chemical and physical stability. Physical stability is the change in the physical form of the drug and chemical stability is a change in the molecular structure through a chemical reaction.

Drug Formulation

Drug formulation is the stage of product manufacturing in which the drug is mixed with all other components to prepare a dosage form for delivery of the drug to the patient. There are four basic components for a successful pharmaceutical formulation, including the active pharmaceutical ingredients, valuable excipients, associated interactions, and manufacturing procedure. Drug formulation is determined by the physicochemical properties of drugs and excipients. Each formulation often functions in a specific dosage form that must be a particular configuration and distributed into a particular dose. The first processing step of a formulation is milling used to ensure that the particle size distribution is adequate for mixing. Next, the drug and excipients are blended or mixed. Once blended, it must then be compressed into a tablet. Finally, the tablet may require a coating, such as a flavor coating and enteric coating to avoid an upset stomach.

Delivery Method

Drug delivery is the process of administering a pharmaceutical compound to patients for therapeutic effect. For many drugs, their therapeutic nature determines the administration route. There are more and more delivery systems available for drug delivery. The delivery method is chosen based on the physicochemical properties of the drug, the duration of action, the desired site of action, and the biological barriers. Some of the most common delivery methods are oral, parenteral, transdermal, and aerosol. In addition, current efforts in other drug delivery methods are vast, including controlled-release formulations, targeted delivery, nanomedicine, drug carriers, 3D printing, and biologic drugs delivery. The physicochemical properties of the drug must be considered in designing a successful drug delivery method.

• Oral Administration
• Parenteral Administration
• Transdermal Administration
• Aerosol Administration
• Other Delivery Methods, such as controlled-release, drug carriers, nanomedicine, etc.

Reference

1. Barich, D., Zell, M. and Munson, E., 2016. Physicochemical Properties, Formulation, and Drug Delivery. Drug Delivery, pp.35-48.