I found the following on this website: https://help.cbp.gov/app/answers/detail/a_id/1160/~/traveling-with-medication
Can I travel with medications and medical devices, such as needles or oxygen tanks?
Prescription medications should be in their original containers with the doctor's prescription printed on the container. It is advised that you travel with no more than personal use quantities, a rule of thumb is no more than a 90 day supply. If your medications or devices are not in their original containers, you must have a copy of your prescription with you or a letter from your doctor. A valid prescription or doctors note is required on all medication entering the U.S.
The U.S. Food & Drug Administration (FDA) is responsible for pharmaceutical admissibility determinations. If you have any questions as to whether a specific pharmaceutical may be imported into the United States, please visit the FDA's website, or call (301) 796-0356.
If you are traveling with medical devices such as needles or oxygen tanks that could pose a security or safety concern to others, be sure to have a copy of the prescription for those items from your doctor. You should also contact the Transportation Security Administration about any additional requirements they may have.