Sildigra 250 mg, or any sildenafil product at such a high dosage, might be banned or restricted due to several reasons:

Safety Concerns: Doses of sildenafil higher than the standard therapeutic range (which usually maxes out at 100 mg) can increase the risk of severe side effects, such as cardiovascular issues, headaches, vision changes, and priapism (a painful, prolonged erection).

Regulatory Standards: Regulatory agencies like the FDA or EMA (European Medicines Agency) set specific dosage limits for medications based on clinical trials and safety profiles. A dose like 250 mg may exceed the recommended limit, leading to potential safety concerns and thus being banned or restricted.

Lack of Clinical Evidence: There might be insufficient clinical research supporting the safety and efficacy of a 250 mg dose. The highest recommended dose for sildenafil is generally 100 mg, and dosages beyond this are not supported by adequate clinical data.

Risk of Counterfeiting: High-dose formulations might also be associated with counterfeit or unregulated products, which can pose significant health risks.

Medical Guidelines: Medical guidelines and best practices typically do not support such high doses due to the increased risk of adverse effects and lack of added benefit over standard doses.

If you come across a product labeled with a dosage significantly higher than what is commonly prescribed, it's crucial to consult a healthcare provider to ensure its safety and appropriateness.