Effect of Compaction Pressure on the Enzymatic Activity of Pancreatin in Directly Compressible Formulations

In recent years, enzymes have found widespread use and are of growing interest in modern medicine. The industrial market for such drugs is expected to grow rapidly in the coming years. Enzymes are selective biocatalysts of high efficiency present in living organisms. In many cases, their enzymatic activity depends on the pH of the environment and temperature. Regarding the latter factor, it should be taken into consideration that as proteins, they can denature at higher temperatures and lose their functionality. In this regard, the optimal temperature can vary from enzyme to enzyme [1,2,3].

Oral solid dosage forms (OSDFs) are still the most preferred option by both drug manufacturers and patients. Among them, tablets are the most widely and willingly used [4]. Nevertheless, the technological processes employed in the production of tablets can significantly decrease enzymatic activity. The safest are dry processes, which do not pose a risk of enzyme decomposition during processing in the presence of water and/or during the following drying [5,6,7]. Therefore, manufacturing of tablets using the direct compression method (DC) seems to be the most appropriate formulation strategy. Nevertheless, the compression forces (compaction pressures) applied during the tableting process can be a key factor potentially affecting enzyme stability [5,8,9]. Schulz et al. revealed that compaction pressure induced a reduction in powder volume, which was the main cause of the loss of enzymatic activity of butyrylcholine esterase and peroxidase during tableting [10].

Similarly, Teng and Groves observed a decrease in enzyme activity during compression of urease [11], and Wurster and Ternik found the same in the case of catalase [8].

It has been reported that the type and nature of excipients incorporated into formulations can affect enzyme stability. Picker found that enzyme inactivation can be mitigated by the employment of excipients that require low compaction pressure and are able to re-lease mechanical stresses during tableting [12]. Graf et al. showed that the use of micro-crystalline cellulose exerted a stabilizing effect on enzymes in pancreatin tablets [13]. However, Kuny and Leuenberger as well as Sharma et al. noticed that at higher concentrations, MCC can induce high shear forces and cause the enzyme particles to be crushed [14,15]. In their study, Sharma et al. linked the loss of model enzyme activity to a decrease in porosity and an associated increase in tablet density under applied compression forces.

This was explained by the collapse of voids (pores) in compressed powders leading to mechanical damage of protein molecules [15]. It should be noted that enzyme powders are not identical and differ in terms of their mechanical properties and deformation characteristics. Consequently, it is important to employ the matching excipients providing a good balance between plasticity and brittleness. This will ensure that the compressed enzyme tablets will have sufficient mechanical properties and the required performance without losing the activity of the active ingredient.

The subject matter of the presented research was pancreatin, which is a dry extract of fresh animal pancreas. It contains a combination of several digestive enzymes with amylolytic, proteolytic, and lipolytic activities that are activated in the alkaline pH in the small intestine [16,17]. Pancreatin has been used for many years to treat digestive disorders caused by insufficient secretion of pancreatic enzymes. In addition, pancreatin supplementation has long been widely used by athletes [18,19].

Commercial products are marketed as dietary supplements, over-the-counter (OTC) and prescription (Rx) medications, in the form of enteric-coated powders, granules, capsules, or tablets [20,21].

Marketed products are characterized by a fairly wide variety of enzyme compositions and activities, which very often do not match those declared. Löhr et al. analyzed several commercial formulations of pancreatic enzymes in terms of their enzyme activities [22]. They found significant variation from the declared contents, which for lipase changed from 93% to 115%, for amylase from 97% to 233%, and for protease from 120% to 281%. Maev et al. determined the strengths of the commercial pancreatin products by determining lipase activity [23]. Determined enzyme activities expressed as a percentage of labeled lipase activity in various products ranged from 79% to 122%. A similar approach was presented by Kuhn et al. [24] and Shrikhande et al. [25]. The products tested differed significantly in the percentage relationship between labelled and assayed lipase activity, which ranged from 102% to 187% in the former case, and from 55% to 120% in the latter.

The aim of the present study was to develop directly compressible formulations of pancreatin. Furthermore, to investigate how factors acting on compressed powders affect the pancreatin content and its enzymatic activity. The study also examined the impact of the compression force (compaction pressure) or the tableting speed affected the characteristics of the tablets (density, hardness, friability, disintegration). The analyzed factors additionally included ejection forces and the temperature generated during the compression process. The latter parameter was analyzed with the help of a thermal imaging camera.

The synergistic action of two excipients showing a different deformation mechanism, i.e., plastic microcrystalline cellulose and brittle calcium phosphates, was utilized in the formulation design. Such a combination gives powder mixtures the desired flowability and allows the preparation of tablets with good mechanical strength, rapid disintegration, and fast release of a drug substance [26]. Moreover, the application of highly porous grades of calcium phosphates in the formulation allows the matrix of the tablets to maintain an adequate level of porosity, preventing a strong reduction in volume during com-pression and preventing damage to the enzyme molecules [27].

Pancreatin (from porcine pancreas) EMPROVE^® ESSENTIAL USP was from Merck KGaA (Darmstadt, Germany). Anhydrous dibasic calcium phosphate, DCPA (DI-CAFOS^® A150), tribasic calcium phosphates, TCPs (TRI-CAFOS^® 500 and TRI-CAFOS^® 200-7) were produced by Chemische Fabrik Budenheim KG (Budenheim, Germany). Low-substituted hydroxypropyl cellulose, L-HPC (LH-11) was provided by ShinEtsu (Wiesbaden, Germany). Microcrystalline cellulose, MCC (VIVAPUR^® 102 was from JRS Pharma (Rosenberg, Germany), Magnesium stearate (Ligamed^® MF-2-V) was supplied by Peter Greven Fett-Chemi (Venlo, The Netherlands).