MCT Oil in Pharmaceuticals and Its Applications as an Excipient

1. Characteristics and Properties of MCT Oil

Medium-chain triglycerides (MCT oil) are a mixture of triglycerides produced by the esterification reaction between glycerol and the fatty acids Caprylic acid and Capric acid derived from coconut oil or palm oil, with the following properties:

• Oil form, colorless or pale yellow, odorless, and tasteless
• HLB value: 1
• Solidification temperature: 0°C
• Insoluble in water, readily soluble in methanol, and miscible with methylene chloride, soybean oil, and other petroleum ethers

2. Applications of MCT Oil in Pharmaceutical Manufacturing

a. MCT Oil as an Energy Source

• Function: Provides energy to the body
• Used in injectable and infusion products
• Suitable for health supplement products providing energy and nutrition

b. Applications of MCT Oil in Oral Pharmaceuticals

Oral pharmaceuticals:

• Tablets: Lubricant and anti-sticking agent for punches and dies
• Hard capsules and sugar-coated tablets: Agent that helps increase the intestinal absorption of active ingredients
• Softgel capsules: Oil carrier for the fill formulation, providing energy and improving the solubility of poorly soluble active ingredients
• Liquid formulations: MCT oil is used in emulsions, microemulsions, self-emulsifying systems, solutions, and suspensions containing active ingredients that are unstable or poorly soluble in water, such as Calciferol
• Parenteral pharmaceuticals: Solubilizing agent for lipophilic drug substances in oil-based injectable solutions, emulsions, and injectable suspensions, helping improve the solubility and absorption of active ingredients
• Topical pharmaceuticals: Oil-based vehicle for topical preparations, improving the solubility and bioavailability of lipophilic active ingredients
• Suppositories: Base for suppositories
• Used as an alternative antimicrobial agent in pharmaceutical formulations

3. Advantages of MCT Oil in Pharmaceutical Formulations

• Acts as a solvent for lipophilic active ingredients in pharmaceutical formulations, helping improve solubility and increase the bioavailability of active ingredients
• Stable against oxidative agentssuch as light and atmospheric oxygen
• Chemically inert, with no incompatibility with other active ingredients and excipients
• Contains no antioxidants, residual solvents, or catalysts
• High active ingredient loading capacity
• Due to its shorter chain length, it israpidly metabolized and absorbed in the digestive system, helping increase the bioavailability of active ingredients
• For softgel capsules: The use of MCT oil in the fill formulation helps reduce the risk of cross-linking in the capsule shell, which can cause shell hardening, leakage, and difficulties in shell disintegration
• For topical preparations: The use of MCT oil helps improve the spreadability of the formulation on the skin without affecting the skin's respiratory function, facilitating effective delivery of active ingredients through the skin without causing dryness
• The product has high purity and is manufactured through a strictly controlled process, thereby ensuring good and consistent product quality

4. Mechanism of MCT Oil in Reducing Cross-Linking in Softgel Capsules

The mechanism by which MCT helps reduce cross-linking in softgel capsules does not involve inhibiting the reaction between amino groups and carbonyl groups, which is the primary reaction responsible for cross-linking. Instead, it is attributed to the chemical inertness and purity of this material compared with other oils having the same HLB value of 1. Some properties of MCT that help reduce cross-linking in softgel capsules are as follows:

a. Extremely Low Aldehyde and Peroxide Levels

Poorly refined vegetable oils often contain unsaturated fatty acids. Over time, these double bonds undergo oxidation to form hydroperoxides, which subsequently decompose into Aldehydes. These Aldehydes are the primary factors that interact with the gelatin capsule shell to form cross-links, resulting in cross-linking.

In contrast, MCT, typically consisting of C8 and C10 fatty acids, is composed of fully saturated fatty acids with no double bonds, making it highly resistant to oxidation. When MCT is used as a solvent for dissolving lipophilic active ingredients, the concentration of generated Aldehydes is nearly zero.

b. Moisture Content and Polarity

Cross-linking requires an aqueous environment to facilitate ionization reactions. MCT has low polarity and a lower moisture-absorbing capacity compared with polar solvents such as PEG 400:

When PEG 400 is used as a solvent, it tends to draw water from the capsule shell into the excipient or absorb moisture from the environment, increasing the rate of hydrolysis and cross-link formation, thereby increasing the risk of cross-linking.

MCT creates a hydrophobic barrier that maintains the physical and mechanical stability of the capsule shell and limits water migration from the shell, thereby reducing the risk of cross-linking.

c. Compatibility

MCT does not dissolve the gelatin capsule shell and does not penetrate the capsule shell structure as strongly as surfactants or strong organic solvents. This helps maintain the balance of the gelatin network and plasticizer:

• When PEG 400 is used: PEG has a strong affinity for water and glycerin. It tends to draw glycerin from the capsule shell into the fill. As a result, the shell loses its plasticizer, becoming brittle and more prone to cracking.
• When MCT is used: Glycerin is completely insoluble in MCT. Therefore, glycerin remains within the gelatin network of the capsule shell, allowing the shell to retain its flexibility and elasticity.