Review on Starter Pellets: Inert and Functional Cores

A significant proportion of pharmaceuticals are now considered multiparticulate systems. Modified-release drug delivery formulations can be designed with engineering precision, and patient-centric dosing can be accomplished relatively easily using multi-unit systems. In many cases, Multiple-Unit Pellet Systems (MUPS) are formulated on the basis of a neutral excipient core which may carry the layered drug surrounded also by functional coating. In the present summary, commonly used starter pellets are presented. The manuscript describes the main properties of the various nuclei related to their micro- and macrostructure. In the case of layered pellets formed based on different inert pellet cores, the drug release mechanism can be expected in detail. Finally, the authors would like to prove the industrial significance of inert cores by presenting some of the commercially available formulation.

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About this article: Kállai-Szabó, Nikolett, Miléna Lengyel, Dóra Farkas, Ádám T. Barna, Christian Fleck, Bálint Basa, and István Antal. 2022. “Review on Starter Pellets: Inert and Functional Cores” Pharmaceutics 14, no. 6: 1299.

Table 1. Commercially available starter spheres*

Pellet Core Material–Main ComponentBrand Name (Manufacturer)
SucroseSuglets (Colorcon; Bazainville; France); Pharm-a-spheres (pharm-a-spheres GmbH; Tornesch; Germany); Surinerts (IPS srl, Milan, Italy); Vivapharm Sugar Spheres (JRS Pharma GmbH&Co.KG.; Weissenborn; Germany); Sugar pellets (Umang Pharmatech Pvt Ltd.; Thane; India)
Microcrystalline cellulose (MCC)Vivapur® MCC spheres (JRS Pharma GmbH&Co.KG.; Weissenborn; Germany); Cellets (IPC Process-Center GmbH; Dresden; Germany); CELPHERE™ (Asahi Kasei Corporation; Tokyo; Japan); MCC Pellets MS (Umang Pharmatech Pvt Ltd.; Thane; India)
IsomaltgalenIQ (Beneo GmbH; Mannheim; Germany)
Anhydrous dibasic calcium phosphatePharSQ Spheres CM (Chemische Fabrik Budenheim; Budenheim; Germany)
Tartaric acidTAP (IPC Process-Center GmbH; Dresden; Germany); Tartaric acid pellets (Umang Pharmatech Pvt Ltd.; Thane; India); InstaSpheres-TA (Tartaric acid spheres seal coated with hydrophilic polymer; Ideal Cures; Mumbai; India)
SilicaSilica Pellets AS (Umang Pharmatech Pvt Ltd.; Thane; India)
XylitolXylinerts (Gustave Parmentier GmbH, Germany)
MannitolMannitol spheres SANAQ®(Pharmatrans SANAQ; Basel; Switzerland)
LactoseLactose pellets LS (Umang Pharmatech Pvt Ltd.; Thane; India)
Calcium carbonateCalcium carbonate SANAQ??(Pharmatrans SANAQ; Basel; Switzerland); Calcium Carbonate Pellets CS (Umang Pharmatech Pvt Ltd.; Thane; India)
StarchStarch Pellets STS (Umang Pharmatech Pvt Ltd.; Thane; India)


* Remarks from pharmaexcipients: Surinerts are made by IPS srl, Milano, Italy and have been changed in this table accordingly – Xylinerts are made by Gustav Parmentier GmhB, Germany (not sure if still commercially available)

Today various starter pellets are commercially available. The cores have several particle size fractions in a narrow size range prepared for the pharmaceutical industry as ready-to-use excipients for drug layering techniques. The manuscript presents the most often used inert cores in the pharmaceutical industry, along with the process of drug layering. The main properties of inert pellets, which may be decisive in the development of a multiparticulate formulation, where the active ingredient surrounds the surface of an inert pellet core, have been described in detail. Numerous commercially available formulations have also been presented. This reflects the use of the starter pellet as an excipient in a wide variety of active ingredients and dosage forms. It is important to note that no so-called universal standard exists among the various inert pellet cores that could be applied to all active ingredients or film coatings. For each drug technology development, the type and size fraction of the starter pellets must be selected according to the particular active ingredient, dosage strength, and dosage form. For the right decision, it is essential to have as much knowledge as possible about inert pellet cores.

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