In the Philippines, senior citizens are entitled to a 20% discount on medicines under Republic Act No. 9994, also known as the Expanded Senior Citizens Act. To avail of this discount, seniors must present their senior citizen ID or a valid identification card that states their age when purchasing medications. It's important to check with the pharmacy, as some establishments may have specific policies regarding the application of this discount. For more detailed information, you may consult the official government guidelines or speak to a licensed pharmacist.