Therapeutic duplication would be a concern for a patient prescribed which of the following medications, if also receiving another medication with similar effects?

Guaifenesin is an expectorant used to relieve chest congestion. It does not have overlapping therapeutic effects with other medications, as it primarily functions to thin mucus in the airways. Therefore, the concern for therapeutic duplication does not apply in this case.

Tamoxifen is a selective estrogen receptor modulator used in breast cancer treatment. While it has specific therapeutic effects, it does not overlap with those of other medications in a way that would lead to therapeutic duplication. The risk of adverse interactions with other cancer therapies exists, but it is not classified as therapeutic duplication.

Baclofen is a muscle relaxant used to treat spasticity. While it can interact with other muscle relaxants, it is not typically associated with therapeutic duplication in the same way that doxazosin is with alpha-blockers. Its mechanism of action differs enough to reduce the concern for overlapping effects.