You should be able to!
As long as it is informed consent on your part. And by informed consent, I do not mean you need to be an expert on pharmacology, only that you understand that pharmacologists have identified risks, and you understand the general magnitude and nature those risks.
But, the pharmacist (or anyone else accepting your waiver) is not responsible for determining your level of understanding. They only need to determine that you are a competent adult, and that you understand that a claim to understand the risks enumerated in the waiver is a legally binding transfer of responsibility for those risks and your understanding of them.
In general, the greater your understanding of the risks of a particular activity, the greater the risk that you should be able to consent to in that activity. If you claim understanding in a legal document (a waiver), you should be legally responsible for any deficiency in your understanding.