Sublingual Drug Delivery Systems: Quality by Design Principles, Applications, Market Landscape, and Innovative Technologies.

One promising alternative to the oral approach is drug administration via the oral mucosa. Sublingual refers to the administration of drugs through the mouth that are rapidly absorbed by the blood vessels "under the tongue." In terms of efficacy and patient compliance, the sublingual route is better than the oral route of delivery. Sublingual drug delivery systems provide a rapid onset of action, bypass first-pass liver extraction in the gastrointestinal route, and achieve high bioavailability through enzymatic degradation. This article highlights the quality-by-design philosophy, the everchanging market environment, and innovative sublingual drug delivery systems. A methodical approach to drug creation known as Quality by Design (QbD) emphasises incorporating quality into a product from the start rather than testing it after the fact. QbD ensures a robust, well-understood production process and a high-quality, safe, and effective sublingual product. Particularly for biomolecules and poorly soluble drugs, innovative technologies for sublingual drug delivery systems concentrate on increasing patient compliance, prolonging retention duration, and optimising drug absorption. 3D printing, sophisticated polymer systems, and micro- and nanotechnologies are instances of emerging strategies. The regulatory framework and current state of clinical trials in this field are also critically analyzed in this narrative review.