Specialized Equipment Improves Tableting

For many reasons-from ease of administration to dosing accuracy to manufacturing efficiency-pharmaceutical manufacturers prefer to formulate their APIs as solid dosage drugs, and particularly tablets. There is significant room, however, for improvement of tableting processes.

Tablet press lubrication
Lubricants (commonly magnesium stearate) affect the tableting process and the finished tablet. They not only reduce the compression force during tableting, but also prevent product buildup on tablet press tools and give the tablet a smooth surface. Too much lubricant can, however, reduce the hardness of the tablet to an undesired level, according to Sharon Nowak, business development manager with Coperion K-Tron Food & Pharmaceutical Industries. Traditionally, lubricants have been mixed with the solids used to form tablets, but this approach often leads to non-uniform distribution of the lubricant. To compensate, excess lubricant is used, which can negatively affect tablet properties.

Recently, equipment has been developed that allows for spraying of the lubricant onto the tablet press tooling, allowing for significant reduction in the quantity of lubricant required. Original systems sprayed powdered lubricants on to the tablet press tooling to prevent sticking of the powder to the tool and die of the tablet press, according to Nowak. Importantly, these applications were done primarily volumetrically, with no measurement of the actual weight of the lubricant delivered. Magnesium stearate does not flow well, which can cause high variations in the feed rate with volumetric feeders because of inconsistent filling of the twin screws. As a result, there has been an increased demand for automated tablet press lubrication systems with highly accurate gravimetric feed designs, according to Nowak.

“High accuracy twin-screw gravimetric feeders quantitatively deliver a specific amount of lubricant to the tablet. They also allow accurate determination of the amount of lubricant delivered to each tablet, even though the quantity of lubricant that ends up in the tablet granulation formulation is significantly decreased,” she observes. As a result, not only are the material handling properties of the granulation process improved, the overall dissolution rates of tablets can be increased. The lower quantities of lubricants required for tableting have also led to a need for lower and lower feed rate deliveries, according to Nowak. “For this reason, automated lubricant feeding systems today require highly accurate, specialized low-rate feeding,” she says.

Coperion K-Tron’s solution uses patented load cell technology that continuously measures the weight of the lubricant and maintains a constant mass flow (weight per unit of time) by adjusting the speed of the twin-screw feeder. As a result, according to Nowak, the unit can be validated for a steady and uniform feed of lubricant to the tablet press. In addition, because the lubricant is delivered to the tools in a fraction of a second, the short-term accuracy is high. “With a nearly constant feed rate, it is possible to achieve uniform coating of the tablet tools and eliminate sticking problems, all with reduced stearate consumption and lower overall operating costs,” Nowak states.

Multi-tipped tooling and advanced coatings
The key drivers in tablet manufacturing are the need to increase yield and capacity while reducing manufacturing costs and minimizing the space used and the time spent setting up each press, and increasing productivity has always been a challenge in modern tablet production, according to Steve Deakin, owner director of I Holland. That is why he believes the widespread use of multi-tipped tooling and the continued development of punch-and-die treatments and coatings have been great advances in the pharmaceutical industry.

“Our ongoing development of multi-tip tooling is specifically driven by the desire to assist our customers in increasing productivity and capacity,” he says. Multi-tip punches allow the number of tablets per turret rotation to be multiplied by the number of tips on the punch. They also require less floor space, because more tablets can be produced with fewer tablet presses, leading to a reduction in overall plant running costs. “The development of a technology like multi-tip tooling is beneficial to many end users,” says Deakin.

With respect to treatment and coating technologies, I Holland categorizes them based on their function: improving wear resistance, improving corrosion resistance, and improving anti-stick properties. “Treatments and coatings with these properties can help preserve the life of our punches and increase productivity for our customers,” Deakin comments. “The overall result is reduced press downtime and increased productivity, which is what every company wants,” he adds.

About the Author
Cynthia A. Challener, PhD, is a contributing editor to Pharmaceutical Technology. Read the complete article by Cynthia Challener, with additional discussion of continuous manufacturing, systems integration, and modeling, in the Pharmaceutical Technology Solid Dosage e-book.

Learn More from Sharon Nowak and Others at Interphex
On Tuesday, April 21, from 2:15-4 pm, Pharmaceutical Technology will host solid dosage manufacturing experts on the Innovation Stage. Come hear Sharon Nowak, Business Development Manager, Coperion K-Tron Food & Pharmaceutical Industries, speak about Optimization of Feeding and Conveying Technologies for Difficult Flowing Pharmaceutical Powders; Martin Hack, vice-president and general manager, L.B. Bohle, speak about Fluid Bed Technologies for Improved Processing; and Fred Murray, president, Korsch America, speak about Multi-Layer Tableting Technology.  For more details, see our Educational Programming page.