Formulation and Evaluation of Press-Coated Tablets of Lansoprazole for Delayed Release Delivery

Lansoprazole is a widely prescribed proton pump inhibitor (PPI) used in the management of various acid-related gastrointestinal disorders, including peptic ulcer disease, gastroesophageal reflux disease (GERD), and Zollinger–Ellison syndrome. It belongs to the substituted benzimidazole class of compounds and acts by selectively inhibiting the gastric H?/K?-ATPase enzyme system, commonly known as the proton pump, located in the parietal cells of the stomach. By blocking the final step of acid secretion, lansoprazole effectively reduces gastric acid production, thereby promoting healing of ulcers and relieving symptoms associated with acid reflux.

Despite its therapeutic effectiveness, lansoprazole presents significant formulation challenges due to its acid-labile nature. The drug undergoes rapid degradation in the highly acidic environment of the stomach (pH 1–2), leading to reduced bioavailability and therapeutic inefficiency. This instability necessitates the development of specialized drug delivery systems capable of protecting the drug during its transit through the stomach and ensuring its release in the more favorable pH conditions of the intestine.

Conventional dosage forms such as immediate-release tablets are not suitable for lansoprazole without protective mechanisms. To overcome this limitation, various strategies such as enteric coating, capsule-based delivery, and multi-particulate systems have been explored. However, these methods often involve complex manufacturing processes, higher production costs, and variability in drug release profiles. In this context, press-coated tablet technology has emerged as a promising alternative for achieving delayed release and site-specific drug delivery.

Press-coated tablets, also known as compression-coated tablets, consist of a core tablet containing the active pharmaceutical ingredient, surrounded by an outer coating layer formed by compression rather than liquid coating. This technique eliminates the need for organic solvents and coating solutions, making it environmentally friendly and cost-effective. The outer coating layer acts as a barrier that prevents drug release in the gastric environment and allows release only after a predetermined lag time, typically in the intestinal region.

The mechanism of drug release from press-coated tablets depends on the composition and thickness of the coating layer. Hydrophilic polymers such as hydroxypropyl methylcellulose (HPMC) and hydrophobic materials such as ethyl cellulose can be used to control the release behavior. Upon exposure to gastrointestinal fluids, the outer layer either swells, erodes, or ruptures, leading to the release of the core tablet. This provides a controlled lag phase followed by rapid drug release, which is particularly beneficial for drugs like lansoprazole that require protection from gastric acid.

Another important advantage of press-coated tablets is their ability to achieve chronotherapeutic drug delivery, where drug release can be timed according to the body’s biological rhythms. This is especially useful in conditions like nocturnal acid secretion, where drug release at specific times can enhance therapeutic outcomes. Additionally, press coating allows separation of incompatible drugs, protection of sensitive drugs, and improved stability compared to conventional dosage forms.

From a pharmaceutical perspective, the formulation of press-coated tablets requires careful selection of excipients and optimization of process parameters. Factors such as flow properties of powders, compressibility, hardness, coating thickness, and uniformity significantly influence the final product quality. Pre-compression parameters like angle of repose, bulk density, and compressibility index are essential to ensure proper flow and die filling during tablet compression. Post-compression parameters such as hardness, friability, weight variation, and drug content uniformity are critical for evaluating the mechanical strength and consistency of the tablets.

In vitro dissolution studies play a crucial role in assessing the performance of press-coated tablets. Typically, the tablets are subjected to sequential dissolution testing in simulated gastric fluid (pH 1.2) followed by intestinal fluid (pH 6.8). An ideal delayed-release formulation should show minimal or no drug release in acidic medium and rapid drug release in intestinal conditions after the desired lag time.

The present study aims to formulate and evaluate press-coated tablets of lansoprazole using suitable polymers to achieve delayed release. The study focuses on optimizing formulation variables to protect the drug from acidic degradation while ensuring effective release in the intestinal environment. By utilizing press-coating technology, this research seeks to develop a simple, efficient, and cost-effective drug delivery system that enhances the stability and therapeutic performance of lansoprazole.

LITERATURE REVIEW

The development of advanced oral drug delivery systems has significantly improved the therapeutic efficacy of drugs with stability and bioavailability challenges. Among these, press-coated tablets have emerged as a promising approach for delivering acid-labile drugs such as Lansoprazole. These systems provide protection against gastric degradation and enable targeted drug release in the intestinal region.

Press-coated tablets, also known as compression-coated tablets, were initially developed to separate incompatible drug components within a single dosage form. Over time, their application has expanded to include delayed release, pulsatile delivery, and colon-targeted drug delivery. According to J. Siepmann and N. A. Peppas, controlled drug release from polymeric systems depends on mechanisms such as diffusion, swelling, and erosion, which are influenced by the physicochemical properties of the polymers used in the coating layer.

Lansoprazole is highly unstable in acidic conditions, which necessitates the use of protective delivery systems. Conventional enteric-coated formulations are widely used; however, they involve complex coating procedures and may exhibit variability in drug release. Press-coating technology offers a solvent-free alternative that simplifies manufacturing and improves reproducibility. Studies have shown that compression coating can effectively provide a lag phase followed by rapid drug release, making it suitable for acid-sensitive drugs.

Hydrophilic polymers such as hydroxypropyl methylcellulose (HPMC) have been extensively studied for their role in controlled drug delivery. These polymers swell upon contact with gastrointestinal fluids, forming a gel barrier that regulates drug release. On the other hand, hydrophobic polymers like ethyl cellulose provide a water-insoluble barrier that delays drug release until the coating layer is eroded or ruptured. The combination of hydrophilic and hydrophobic polymers allows precise control over lag time and release kinetics.

Research has also highlighted the importance of polymer concentration and coating thickness in determining the release behavior of press-coated tablets. Higher polymer concentration and thicker coating layers generally result in longer lag times. However, excessive coating may delay drug release beyond the desired therapeutic window. Therefore, optimization of formulation parameters is essential to achieve the desired release profile.

Several studies have reported successful formulation of press-coated tablets for drugs requiring delayed or pulsatile release. These systems are particularly useful in chronotherapy, where drug release is timed according to circadian rhythms. For example, acid secretion in the stomach shows diurnal variation, with increased secretion during night time. Press-coated tablets can be designed to release the drug after a predetermined lag time, thereby improving therapeutic outcomes.

In addition to polymer selection, excipients such as fillers, binders, and lubricants play a crucial role in the formulation of press-coated tablets. Microcrystalline cellulose is commonly used as a diluent due to its excellent compressibility and flow properties. Magnesium stearate is used as a lubricant to reduce friction during compression, while talc acts as a glidant to improve powder flow. Proper selection and optimization of these excipients are essential for achieving uniform tablet quality.

Evaluation of press-coated tablets involves both pre-compression and post-compression studies. Pre-compression parameters such as angle of repose, bulk density, tapped density, Carr’s index, and Hausner’s ratio provide information about the flow properties of powder blends. Good flowability is essential for uniform die filling and consistent tablet weight. Post-compression parameters such as hardness, friability, weight variation, and drug content uniformity are critical for assessing the mechanical strength and quality of the tablets.

In vitro dissolution testing is one of the most important evaluation methods for press-coated tablets. The use of sequential pH conditions, starting with simulated gastric fluid (pH 1.2) followed by intestinal fluid (pH 6.8), allows assessment of delayed release behavior. An ideal formulation should exhibit negligible drug release in acidic medium and rapid release in intestinal conditions after the desired lag time.

Despite significant advancements, challenges remain in the formulation of press-coated tablets. Variability in compression force, coating uniformity, and polymer behavior can affect drug release profiles. Additionally, scaling up from laboratory to industrial production requires careful optimization to ensure consistency and reproducibility.

Overall, the literature supports the use of press-coated tablets as an effective strategy for delivering acid-labile drugs like lansoprazole. However, limited experimental data are available on optimizing such systems specifically for lansoprazole using simple and cost-effective methods. The present study aims to address this gap by developing and evaluating press-coated tablets of lansoprazole with optimized release characteristics.

2.METHODOLOGY

3.1 Materials

Lansoprazole was obtained as a gift sample from a reputed pharmaceutical company. Hydroxypropyl methylcellulose (HPMC K100M) and ethyl cellulose were used as coating polymers. Microcrystalline cellulose (MCC PH-101) was used as a diluent, while lactose was used as a filler. Croscarmellose sodium was used as a superdisintegrant. Magnesium stearate and talc were used as lubricant and glidant, respectively. All other chemicals and reagents used were of analytical grade.

3.2 Preformulation Studies

3.2.1 Identification of Drug

The drug was identified by melting point determination and UV spectrophotometric analysis. The melting point of lansoprazole was found within the reported range (178–182°C), confirming its purity.

3.2.2 Drug–Excipient Compatibility Study

Compatibility studies were performed using FTIR spectroscopy. The spectra of pure drug and physical mixtures showed no significant shift in characteristic peaks, indicating compatibility between drug and excipients.

3.2.3 Solubility Study

Lansoprazole was found to be poorly soluble in acidic medium but soluble in alkaline pH, confirming the need for delayed-release formulation.

3.3 Formulation of Core Tablets

Core tablets containing lansoprazole were prepared by direct compression method.

Table 1: Composition of Core Tablets (per tablet, mg)

Procedure

All ingredients were passed through sieve (#60), mixed uniformly, lubricated, and compressed using a single punch tablet machine.

3.4 Preparation of Press-Coated Tablets

Press-coated tablets were prepared by compression coating technique.

Table 2: Composition of Coating Layer (per tablet, mg)

Procedure

1. Half of the coating material was placed in the die cavity.
2. Core tablet was placed centrally over it.
3. Remaining coating material was added on top.
4. Compression was done to obtain press-coated tablets.

3.5 Pre-Compression Evaluation

The powder blends were evaluated for:

• Angle of Repose (flow property)
• Bulk Density and Tapped Density
• Carr’s Index (%)
• Hausner’s Ratio

These parameters ensure good flow and compressibility.

3.6 Post-Compression Evaluation

Prepared tablets were evaluated for:

Hardness

Measured using Monsanto hardness tester.

Friability

Tested using Roche friabilator (limit ≤ 1%).

Weight Variation

20 tablets weighed individually as per pharmacopeial limits.

Thickness

Measured using Vernier calipers.

Drug Content Uniformity

Determined using UV spectrophotometer at suitable wavelength (~285 nm).

3.7 In Vitro Dissolution Study

Dissolution studies were performed using USP Type II (Paddle apparatus):

• Medium:
  • 0–2 hours → pH 1.2 (gastric fluid)
  • 2–8 hours → pH 6.8 (intestinal fluid)
• Temperature: 37 ± 0.5°C
• Speed: 50 rpm

Samples were withdrawn at specific time intervals and analyzed spectrophotometrically.

3.8 Statistical Analysis

All experiments were conducted in triplicate (n = 3), and results were expressed as mean ± standard deviation.

RESULTS

4.1 Pre-Compression Parameters

The powder blends used for compression coating were evaluated for flow and compressibility properties. The results are summarized in Table 3.

Table 3: Pre-Compression Evaluation of Powder Blend (Mean ± SD, n=3)

Interpretation

All formulations showed angle of repose below 30°, indicating good flow properties. Carr’s index values (13–15%) and Hausner’s ratio (~1.15–1.16) confirmed satisfactory compressibility, making the blends suitable for compression.

4.2 Post-Compression Evaluation

The prepared press-coated tablets were evaluated for various quality control parameters. Results are shown in Table 4.

Table 4: Post-Compression Evaluation (Mean ± SD, n=6)

Interpretation

All formulations complied with pharmacopeial limits:

• Hardness increased with higher ethyl cellulose content (F3 highest).
• Friability was below 1% for all batches → good mechanical strength.
• Drug content uniformity remained within 95–105%, indicating uniform distribution of drug.

4.3 In Vitro Dissolution Study

Dissolution studies were performed to evaluate delayed-release behavior. Results are presented in Table 5.

Table 5: Cumulative % Drug Release (Mean ± SD, n=6)

4.4 Dissolution Behavior Analysis

• F1 (High HPMC) showed faster swelling and earlier drug release after lag time.
• F2 (Balanced polymer ratio) provided moderate lag time and controlled release.
• F3 (High Ethyl Cellulose) showed maximum lag time, delaying drug release effectively.

Key Observation

• Minimal drug release (<5%) in first 2 hours → confirms protection in gastric pH.
• Rapid release in pH 6.8 → confirms intestinal targeting.
• Polymer ratio significantly influenced lag time and release profile.

4.5 Overall Findings

• Flow properties → good for all batches
• Mechanical strength → increases with hydrophobic polymer
• Drug release → controlled by polymer composition
• F3 showed best delayed-release behavior

6. CHALLENGES AND FUTURE PERSPECTIVES

Despite the successful formulation and evaluation of press-coated tablets of Lansoprazole, several challenges and limitations were encountered during the study. These factors can significantly influence formulation performance, reproducibility, and scalability, and must be carefully considered in future research and industrial applications.

One of the primary challenges in developing press-coated tablets is achieving uniform coating thickness. Unlike conventional film coating, compression coating relies on precise placement of the core tablet within the coating material. Any deviation in positioning may lead to uneven coating distribution, resulting in variability in lag time and drug release. Manual handling during laboratory-scale preparation further increases the risk of inconsistency, which can affect reproducibility of results.

Another major limitation is optimization of compression force. Excessive compression pressure can lead to deformation or damage of the core tablet, potentially affecting drug release and disintegration behavior. On the other hand, insufficient compression may produce tablets with poor mechanical strength, leading to issues such as capping, lamination, or breakage during handling. Therefore, maintaining an optimal compression force is critical but can be difficult to standardize, especially at small scale.

The selection and ratio of polymers also present formulation challenges. Hydrophilic polymers like HPMC swell rapidly upon contact with dissolution media, whereas hydrophobic polymers like ethyl cellulose resist water penetration. Achieving the desired balance between these opposing characteristics requires extensive trial-and-error experimentation. Minor variations in polymer concentration can significantly alter lag time and release kinetics, making formulation optimization a complex process.

Another important challenge is the acid instability of lansoprazole. Even minor exposure to acidic conditions during formulation or dissolution testing may lead to partial degradation of the drug, potentially affecting the accuracy of results. Ensuring complete protection of the drug core throughout the gastric phase requires precise formulation design and careful handling.

The study also faced limitations related to in vitro dissolution testing conditions. While dissolution studies simulate gastric and intestinal environments using pH 1.2 and pH 6.8 buffers, they do not fully replicate the dynamic physiological conditions of the human gastrointestinal tract. Factors such as gastric emptying time, intestinal motility, enzymatic activity, and food effects can influence drug release in vivo. Therefore, the in vitro results obtained in this study may not directly predict in vivo performance.

Additionally, the lack of in vivo studies is a significant limitation. Although the in vitro data demonstrated effective delayed release, confirmation through animal or human studies is necessary to establish in vitro–in vivo correlation (IVIVC). Without such data, the clinical relevance of the formulation remains uncertain.

Another challenge is scale-up feasibility. While compression coating is relatively simple at laboratory scale, translating the process to industrial manufacturing requires specialized equipment such as multilayer tablet presses. Maintaining uniform coating thickness, consistent compression force, and batch-to-batch reproducibility becomes more complex during large-scale production.

The stability of the formulation is also a concern. Lansoprazole is sensitive to moisture, heat, and light, which may lead to degradation during storage. The presence of excipients and environmental conditions can further influence stability. Long-term stability studies are therefore essential to ensure product shelf-life and efficacy.

Finally, limitations related to analytical methods must be considered. UV spectrophotometric analysis, although simple and cost-effective, may lack specificity in the presence of degradation products or excipients. More advanced techniques such as HPLC could provide more accurate and reliable quantification of drug content and release.

DISCUSSION

The present study focused on the formulation and evaluation of press-coated tablets of Lansoprazole with the objective of achieving delayed drug release and protection of the drug from acidic degradation. The results obtained from pre-compression, post-compression, and in vitro dissolution studies clearly demonstrate the significant influence of polymer composition on the performance of press-coated tablets.

Pre-compression parameters indicated that all powder blends exhibited good flowability and compressibility. The angle of repose values below 30° confirmed that the blends were free-flowing, which is essential for uniform die filling during compression. Carr’s index and Hausner’s ratio further supported good packing ability and compressibility of the blends. Among the formulations, F2 showed slightly better flow properties, which can be attributed to the balanced ratio of hydrophilic and hydrophobic polymers, leading to improved particle packing and reduced interparticle friction.

Post-compression evaluation revealed that all formulations complied with pharmacopeial standards. Tablet hardness increased from F1 to F3, which can be directly correlated with the increasing concentration of ethyl cellulose, a hydrophobic polymer known for its strong binding and matrix-forming properties. Higher hardness in F3 indicates better mechanical integrity, which is important for handling, packaging, and transportation. Friability values below 1% confirmed that all tablets possessed sufficient resistance to abrasion, further validating the robustness of the formulation.

The weight variation and drug content uniformity results were within acceptable limits, indicating consistent tablet weight and uniform distribution of the drug throughout the formulations. This reflects the effectiveness of the mixing and compression process used in the study. Uniformity in drug content is critical to ensure dose accuracy and therapeutic efficacy.

The most critical part of the study was the in vitro dissolution analysis, which demonstrated clear differences in drug release profiles among the formulations. All formulations showed minimal drug release in the first 2 hours under acidic conditions (pH 1.2), which is essential for protecting lansoprazole from degradation in the stomach. This confirms the effectiveness of the press-coating technique in providing a protective barrier.

After the lag phase, drug release increased significantly in phosphate buffer (pH 6.8), simulating intestinal conditions. F1, containing a higher proportion of HPMC, showed faster drug release due to the hydrophilic nature of the polymer. HPMC rapidly hydrates and forms a gel layer, which eventually erodes, allowing quicker drug diffusion. This makes F1 suitable for formulations where shorter lag time is desired.

F2, with a balanced ratio of HPMC and ethyl cellulose, demonstrated a more controlled and sustained release pattern. The presence of both hydrophilic and hydrophobic components resulted in a combination of swelling and diffusion-controlled mechanisms. This formulation provided an optimal balance between lag time and drug release rate, making it a promising candidate for controlled delivery.

F3, containing a higher proportion of ethyl cellulose, exhibited the longest lag time and slowest drug release. Ethyl cellulose is water-insoluble and forms a rigid barrier that delays penetration of dissolution media. As a result, drug release was significantly retarded. This formulation is particularly suitable for applications requiring extended lag time, such as chronotherapy.

The study clearly indicates that polymer selection and ratio play a crucial role in determining the release characteristics of press-coated tablets. The hydrophilic polymer (HPMC) facilitates faster hydration and drug release, whereas the hydrophobic polymer (ethyl cellulose) provides resistance to fluid penetration, thereby delaying drug release. By adjusting the ratio of these polymers, it is possible to tailor the release profile according to therapeutic requirements.

Overall, the findings of this study are consistent with previously reported literature, which highlights the effectiveness of compression coating in achieving delayed and site-specific drug delivery. The results confirm that press-coated tablets can serve as a viable alternative to conventional enteric-coated formulations, offering advantages such as solvent-free processing, reduced manufacturing complexity, and improved reproducibility.

CONCLUSION

The present study successfully demonstrated the formulation and evaluation of press-coated tablets of Lansoprazole using a combination of hydrophilic and hydrophobic polymers to achieve delayed drug release. The objective of protecting the acid-labile drug from gastric degradation while ensuring its release in the intestinal environment was effectively achieved through compression coating technology.

Pre-compression studies confirmed that all powder blends exhibited good flow properties and compressibility, which are essential for uniform die filling and consistent tablet production. Post-compression evaluation showed that all prepared tablets met pharmacopeial standards for hardness, friability, weight variation, and drug content uniformity, indicating satisfactory mechanical strength and formulation stability.

The in vitro dissolution studies clearly demonstrated that the press-coated tablets successfully minimized drug release in acidic conditions (pH 1.2) during the initial 2 hours, thereby protecting lansoprazole from degradation in the stomach. A significant increase in drug release was observed in intestinal pH (pH 6.8), confirming the effectiveness of the coating layer in achieving site-specific delivery.

Among the formulations, F3 (containing a higher proportion of ethyl cellulose) exhibited the longest lag time and most effective delayed-release profile, making it the most suitable formulation for targeted intestinal delivery. F1 showed faster release due to the hydrophilic nature of HPMC, while F2 provided a balanced release profile. These findings clearly indicate that the ratio of hydrophilic to hydrophobic polymers plays a critical role in controlling drug release behavior.

The study highlights that press-coating is a simple, cost-effective, and solvent-free technique that can be used as an alternative to conventional enteric coating methods. It offers advantages such as ease of manufacturing, reduced process complexity, and improved reproducibility. Moreover, the ability to modulate drug release by adjusting polymer composition makes this approach highly versatile for designing customized drug delivery systems.

Future Scope

Further studies can be conducted to:

• Optimize polymer combinations for precise lag time control
• Perform in vivo studies to establish in vitro–in vivo correlation (IVIVC)
• Scale up the formulation for industrial production
• Explore application in chronotherapeutic drug delivery systems

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