What is the difference between Asacol (mesalamine) and Asacol HD (mesalamine) for a patient with ulcerative colitis?

Difference Between Asacol and Asacol HD

Asacol HD is simply a higher-strength tablet formulation (800 mg) of the same delayed-release mesalamine as standard Asacol (400 mg), designed to reduce pill burden while delivering the same medication to the terminal ileum and colon. 1, 2

Key Formulation Differences

• Standard Asacol contains 400 mg mesalamine per tablet, while Asacol HD contains 800 mg mesalamine per tablet 3
• Both formulations use identical pH-dependent polymer coating that breaks down at pH ≥6.8 in the terminal ileum, releasing mesalamine in the same location 2
• The only practical difference is tablet strength—Asacol HD allows patients to take fewer tablets to achieve the same total daily dose 3

Dosing Equivalence

• 2.4 g/day dosing: Standard Asacol requires six 400 mg tablets, while Asacol HD requires only three 800 mg tablets 3
• 4.8 g/day dosing: Standard Asacol requires twelve 400 mg tablets, while Asacol HD requires only six 800 mg tablets 3
• The maximum recommended dose for both formulations is 4.8 g/day 4, 2

Clinical Efficacy

• Both formulations deliver mesalamine identically to the colon with the same mechanism of action and pharmacokinetic profile 2
• In the ASCEND II trial, 4.8 g/day of mesalamine using 800 mg tablets (Asacol HD strength) achieved 72% treatment success versus 59% with 2.4 g/day in moderately active ulcerative colitis (p=0.036) 3
• Once-daily dosing with either formulation is as effective as divided doses and significantly improves adherence 5, 1

Practical Advantages of Asacol HD

• Reduced pill burden: Fewer tablets needed per day improves patient adherence, which is a major factor in ulcerative colitis control 5, 6
• Simplified regimen: Taking three tablets once daily (2.4 g) or six tablets once daily (4.8 g) is more convenient than multiple divided doses 5
• Same safety profile: Adverse events are identical between formulations at equivalent doses 3

Important Clinical Considerations

• Standard-dose therapy (2.4-3 g/day) is recommended for mild-to-moderate ulcerative colitis, while high-dose therapy (4.8 g/day) provides superior efficacy in patients with moderate disease activity or suboptimal response to standard doses 1, 4, 3
• Food effects: Both formulations should be taken with food, as high-fat meals increase mesalamine absorption (C_max increased 91%, AUC increased 16%) 2
• Combination therapy: Adding rectal mesalamine (≥1 g/day) to oral therapy is superior to oral therapy alone for extensive or left-sided disease, regardless of which oral formulation is used 1, 7

Common Pitfall to Avoid

• Do not underdose: Doses <2 g/day are significantly less effective than ≥2 g/day for both induction and maintenance of remission 4. Whether using standard Asacol or Asacol HD, ensure patients receive at least 2.4 g/day for active disease 1, 4