Hi Nation,   It is impossible for anyone to answer this question here, as we know nothing about your age, condition, etc. However, with any medication, you should always stick to the exact prescription your doctor wrote. So, if your doctor prescribed 50mg of Phenergan to be taken at once, then the presumption is this is a safe dose for you. But there is always some risk in taking any medication, so even your doctor can't tell you unequivocally that it wouldn't hurt you.   For more information on Phenergan, see this page from Drugs.com. And talk to your doctor directly about what is safe for you to take when it comes to Phenergan, or anything else.   To your health, Kathi