What are softgel capsules?
Simply defined, soft gel capsules are a solid oral dosage form containing a liquid or semi-solid capsule fill with the active ingredient. The fill is encapsulated in a hermetically sealed capsule shell.
Soft capsules are available in various sizes, and most commonly in round, oval, or oblong shapes. Their size is measured in the volumetric unit “minim”, an old unit for the volume of a drop; one minim corresponds to 61.1 µl. The capsule fill can be a lipid or hydrophilic solution or suspension. The capsule shell is formed from a natural polymer, most commonly gelatin of various origins, and is hydrophilic by default.
In this blog post, we’ll quickly outline the history, advantages, and disadvantages of softgel capsules.
What is the history of soft gel capsules?
While soft capsules were known and patented first in the 1830s, the most common process for their commercial-scale production, the rotary-die encapsulation, was patented by R.P. Scherrer in 1933.
In 1934, Scherrer came up with a machine—a rotary die press—that could manufacture soft gelatin capsules for holding medications.
Since then, soft gel capsules have been used across a variety of pharmaceutical industries, and in the 21st century, they have a versatile and widely adopted solution for delivering various medications and supplements.
What are the advantages of soft gel capsules?
Pharmaceutical/ technological advantages
In particular, soft gel capsules have pharmaceutical and technological advantages, among them:
Delivery of drug substances with poor solubility and increase of bioavailability with advanced liquid drug delivery systems
Applicable for a wide range of drug loads
Rapid release of liquid drug substances
Offer natural protection of sensitive compounds against oxidation and light
Standardized processes can be applied to most manufacturing steps
In case the drug substance is dissolved, minimization of content uniformity issues
Possibility to use both lipophilic and hydrophilic matrices for encapsulation
HSE aspects: the exposure to hazardous powders is limited when handling drugs in a liquid formulation, and added value is the protection of the capsule shell
Patient compliance and commercial advantages of soft gel capsules
Soft gel capsules offer not only patient compliance advantages but also commercial benefits. Their easy-to-swallow nature and appealing appearance contribute to enhanced patient adherence. Moreover, their versatility extends to various sizes and shapes, with the added benefit of the capsule shell effectively concealing any undesirable taste and odor.
What about commercial applications? soft gel capsules prove highly advantageous in this area too. They are particularly well-suited for line extensions of over-the-counter (OTC) products. The liquid fill within these capsules implies a rapid onset of action, making them a valuable choice in diverse commercial scenarios.
What are the disadvantages of soft gel capsules?
Still, there are also disadvantages connected to soft capsule products:
Often limited product and development know-how at the IP owner due to outsourcing of development and manufacture to third parties
Low level of automation of manufacturing process, especially encapsulation
Interactions between capsule fill and capsule shell are possible, e.g. migration of components or crosslinking
Complex dissolution method development due to interactions, analytical artifacts, and matrix effects of lipid formulations
As raw materials of natural origin are used, variable quality and performance can be encountered
Higher cost of goods compared to e.g. immediate-release tablets
Often depending on the performance of third parties / CMOs for the supply due to outsourcing
Soft capsules are highly sensitive to increased temperatures and humidity, leading to physical and sometimes chemical instability
Potentially low patient acceptance of materials of animal origin
Modification of release characteristics is difficult
When are soft capsules the right choice for a drug substance?
The selection of an oral dosage form for a drug substance often is driven to tablets by strategic, commercial, or technological considerations, there are cases in which softgel capsules are the most appropriate choice. The main drivers for a decision to develop a soft capsule are typically either bioavailability and solubility challenges (various BCS class II and IV drugs), marketing aspects (especially line extension of OTC drugs), or characteristics of the drug substance (liquid drug substances).
How we can support your softgel development project
Our team offers the following:
+ Decades of experience in solid dosage form development
+ Support in the concept phase to establish the right dosage form for your product
+ Preparation of formulation concepts and target product profiles