Capsules vs. Tablets - Why Capsules are the Preferred Oral Treatment for Fip

Why Harmony & Rose use Capsules for FIP Treatment rather than Tablets  

Introduction 

Feline Infectious Peritonitis (FIP) is a devastating disease that primarily originates in the small intestine, making gastrointestinal health and drug absorption critical factors in successful treatment. GS-441524, the antiviral nucleotide analog used to treat FIP, requires optimal absorption to achieve effective therapeutic levels in the bloodstream. Harmony / Rose FIP treatment capsules are designed to maximize bioavailability while minimizing gastrointestinal distress, two essential components in managing FIP. 

Historically, a significant difference in bioavailability was observed when GS-441524 first became available in open market treatments in both injectable and tablet forms. Clinical experiences showed that the absorption of GS-441524 from tablets was highly inconsistent, with estimates suggesting only 50% absorption, significantly lower than injectable GS-441524. This discrepancy resulted in treatment failures and the need for higher dosing to achieve clinical remission. Given these challenges, we believe that capsules provide a far superior absorption profile compared to tablets, ensuring a more reliable and effective treatment. 

 

Bioavailability of GS-441524 in Capsules vs. Tablets 

Bioavailability refers to the proportion of a drug that enters systemic circulation in an active form. Several factors influence oral drug bioavailability, including dissolution rate, gastric pH, intestinal permeability, and the presence of excipients. Capsules, particularly gelatin-based formulations, provide superior bioavailability compared to tablets for the following reasons: 

Faster Dissolution and Absorption: 

  • Gelatin capsules dissolve within minutes in the stomach, releasing GS-441524 as a fine powder for rapid absorption in the small intestine. 

  • Tablets require disintegration before absorption can occur. Many contain coatings or binders that slow dissolution, delaying the therapeutic onset of GS-441524. Tablets can dissolve in 20 minutes to up to 75 minutes or sometimes only partially dissolve (the undissolved portion is not absorbed). 

Higher Absorption Efficiency: 

  • Injectable GS-441524 has near-complete bioavailability, meaning almost 100% of the administered dose enters circulation, assuming it is injected correctly and tissue integrity is adequate. 

  • Tablet formulations are estimated to be absorbed at only 50%, meaning a significant portion of the drug was not reaching effective levels in the bloodstream. This often led to under-dosing and treatment failures. 

  • We believe that capsules offer a much higher absorption rate than tablets, potentially approaching that of the injectable form. However, further research is needed to confirm the exact plasma concentrations of tablets, injections, and capsules for accurate comparison. 

    Increased Surface Area for Absorption: 

  • Once the capsule dissolves, the powdered GS-441524 is immediately available for uptake across the intestinal lining. 

  • Tablets, being compacted solid forms, require enzymatic breakdown, reducing the drug’s exposure to absorptive surfaces and prolonging the time needed to reach peak plasma levels. 

 

Minimizing Digestive Irritation for Better Treatment Compliance 

Gastrointestinal symptoms such as nausea, vomiting, and diarrhea are common in FIP-infected cats, making it essential to avoid treatments that could exacerbate these issues. Tablets often contain synthetic binders, fillers, and coatings that can irritate the stomach lining, leading to digestive discomfort. This is particularly problematic because it can mask or mimic FIP symptoms, making it difficult to determine whether a cat is experiencing treatment side effects or disease progression. 

Harmony / Rose capsules were specifically formulated to reduce gastrointestinal irritation: 

  • They contain natural fillers like turmeric and elderberry, which not only act as natural colorants but also provide mild anti-inflammatory and immune-supporting properties. 

  • Microcrystalline cellulose, though not a natural ingredient, is an inert filler that ensures stability without interfering with absorption or irritating the stomach. 

  • Unlike many tablets, capsules do not contain synthetic binders or coatings that can cause digestive upset, making them a gentler option for FIP treatment. 

 

The Importance of Administration on an Empty Stomach 

To maximize absorption, Harmony / Rose capsules should be administered on an empty stomach. Food can interfere with drug uptake by altering gastric pH and delaying gastric emptying, which may reduce overall bioavailability. By ensuring consistent dosing in a fasted state, pet parents can enhance the medication’s efficacy. 

However, for cats that are difficult to medicate, some caregivers have successfully opened the capsules and mixed the contents into a small amount of wet food, such as meat-based baby food or broth. While this may slightly modify absorption kinetics, it remains a viable alternative to maintain treatment adherence while ensuring the medication is ingested. 

 

Challenges with Tablets in FIP Treatment 

  • Lower and Unpredictable Absorption: Black market tablets were estimated to be absorbed at only 50%, significantly lower than injectable GS-441524 and likely lower than well-formulated capsules. 

  • Delayed Onset of Action: Tablets take longer to break down, which can delay the time it takes for GS-441524 to reach effective levels in the bloodstream. 

  • Gastrointestinal Side Effects: Tablets often contain synthetic excipients that can contribute to nausea, bloating, and diarrhea, which could interfere with treatment compliance and overall recovery. 

 

Conclusion 

When treating FIP, consistency in dosing and absorption is critical for achieving successful outcomes. Harmony / Rose FIP treatment capsules provide a superior alternative to tablets by ensuring rapid dissolution, enhanced bioavailability, and reduced gastrointestinal irritation. Given the historical evidence that open market tablets were absorbed at only 50%, we believe that well-formulated capsules offer a significantly higher absorption rate of GS-441524. 

By administering capsules on an empty stomach, pet parents can optimize absorption and therapeutic consistency. For those struggling with direct administration, opening the capsule and mixing the contents into a small amount of food remains an alternative, ensuring compliance while maintaining effectiveness. Ultimately, capsules provide a more reliable, better-absorbed, and gentler method for delivering GS-441524, improving treatment outcomes for cats battling FIP. 

 

Note: While oral treatment is highly effective for most cats, injections remain a crucial option in approx. 5% of cases where oral GS-441524 may not be suitable; such as critically ill cats requiring hospitalization, those with severe vomiting or diarrhea, or rare cases of poor oral absorption despite dosage adjustments. 

 

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