“A pharmacist may not dispense a prescription drug if the pharmacist knows or should have known that the prescription was issued…without a valid patient-practitioner relationship.”
Tex. Occ. Code § 562.056a

EPT is potentially allowable.

While the medical board conditions the issuance of prescriptions on a “proper physician-patient relationship, its analyses may be limited in two ways: (1) it applies only to “dangerous drugs” or “controlled substances,” (which does not likely include typical antibiotics used to treat diseases recommended for EPT; and (2) the statute cited requires that prescriptions should be given in a manner “consistent with public health.” This statutory provision suggests that EPT may be possible if consistent with protecting the public’s health. However, no national STD or communicable disease standards are incorporated by reference in the state via statute or regulation.