Involuntary intoxication constitutes an affirmative defense to prosecution when: (1) the accused has exercised no independent judgment or volition in taking the intoxicant; and (2) as a result of his intoxication he did not know that his conduct was wrong or was incapable of conforming his conduct to the requirements of the law he allegedly violated. Torres v. State, 585 S.W.2d 746, 749 (Tex. Crim. App. [Panel Op.] 1979) (citing City of Minneapolis v. Altimus, 306 Minn. 462, 238 N.W.2d 851, 856-57 (Minn. 1976)); Aliff v. State, 955 S.W.2d 891, 893 (Tex. App.--El Paso 1997, no pet.); Juhasz v. State, 827 S.W.2d 397, 406 (Tex. App.--Corpus Christi 1992, pet. ref'd). The first element of this affirmative defense can be satisfied by evidence that the accused: (1) was unaware he had ingested an intoxicating substance; (2) ingested an intoxicant by force or duress; or (3) took a prescribed medication according to the prescription. Heard v. State, 887 S.W.2d 94, 98 (Tex. App.--Texarkana 1994, pet. ref'd); Spriggs v. State, 878 S.W.2d 646, 649 (Tex. App.--Corpus Christi 1994, no pet.); Shurbet v. State, 652 S.W.2d 425, 428 (Tex. App.--Austin 1982, no pet.); accord Lewis Buttles, Comment, CRIMINAL LAW--Defenses--Involuntary Intoxication is a Defense in Texas, 12 ST. MARY'S L.J. 232, 239-40 (1980). Intoxication by prescription medication occurs only "if the individual had no knowledge of possible intoxicating side effects of the drug, since independent judgment is exercised in taking the drug as medicine, not as an intoxicant." Buttles, 12 ST. MARY'S L.J. at 240; accord Altimus, 238 N.W.2d at 857; see also Aliff, 955 S.W.2d at 893 ("nothing indicated that Aliff took the intoxicating drugs unknowingly, or without knowledge of their effect").