To improve stamina and delay ejaculation without sildenafil, you have several effective options. First, topical anesthetic creams or sprays containing lidocaine can be applied before intercourse to reduce sensitivity. Second, prescription oral medications like dapoxetine are specifically designed to help delay climax. Additionally, behavioral techniques, such as the 'start-stop' or 'squeeze' methods, are highly effective in training your body to last longer. Strengthening your pelvic floor muscles through Kegel exercises also improves control. Finally, managing anxiety and maintaining regular physical exercise can naturally boost your stamina. Please consult a doctor to discuss which option is best and safest for you.