Abstract: This article offers a brief introduction to single-layer and multilayer tablets, outlining their basic structural and functional differences

Introduction:

The existence of pills dates back to 1500 BC, yet they remain one of the most common and versatile forms of oral drug delivery today. From minor inconveniences like headaches to life-threatening ailments, pharmacological tablets possess the chemical key to our relief. These tablets can be broadly categorised into single-layer and multilayer designs.

What's the difference?

Single-layer tablets consist of a uniform blend of ingredients compressed into a single solid unit, while multilayer tablets are composed of two or more distinct layers within a singular dosage form. These structural differences define the foundation for a wide range of pharmaceutical formulations and delivery strategies.

Why does it matter?

Single-layer Tablets:

Single-layer tablets have a simpler formulation and manufacturing process, which lowers production costs. Their homogeneous blend ensures dose uniformity, predictable dissolution and fewer stability challenges. This design is preferred for drugs with one active pharmaceutical ingredient (API), where fast action or rapid systemic exposure is desired. This makes it efficient for high-volume and generic medicine manufacturing at lower costs.

Examples of Single-layer Tablets:

• Ibuprophen immediate-release tablets: Single-layer design provides rapid dissolution and absorption, delivering quick analgesic and anti-inflammatory effects, critical for acute pain management.
• Paracetamol (acetaminophen): Single-layer immediate-release ensures fast onset of pain and fever relief.
• Metformin IR: Simplicity in single-layer production suits high-dose requirements and immediate release and gastrointestinal absorption, making it cost-effective for mass production in diabetes management.

Multilayer Tablets:

Multilayer tablets enable the formulation of incompatible APIs in one dosage unit by physical separation. This allows for complex release profiles – for example, combining immediate- and sustained-release for controlled pharmacokinetics in a single tablet, enabling sequential delivery and site-specific targeting. Preventing the need to take multiple tablets, multilayer drugs also promote patient adherence by reducing pill burden.

Examples of Multilayer Tablets:

• Ambien CR (zolpidem extended-release): Bilayer design – one layer for immediate release (to rapidly induce sleep), second layer for sustained-release (to maintain sleep).
• Janumet XR (sitagliptin/metformin ER): Multilayer tablet combining immediate-release sitagliptin and extended-release metformin; improves glycemic control with once-daily dosing, while separating incompatible release requirements.
• Claritin-D (loratadine + pseudoephedrine): Bilayer separates the antihistamine (immediate-release) from the decongestant (extended-release), optimising symptom relief and duration.

Conclusion:

In understanding the distinction between single-layer and multilayer tablets, formulators and industry professionals can make more informed choices that align with therapeutic goals, manufacturing capabilities, and patient needs. Recognising these foundational differences is essential for developing effective, reliable, and patient-friendly oral-dosage forms of medication. By thoughtful selection of an appropriate tablet design, the industry can continue to advance drug delivery technologies and meet evolving healthcare demands.