(a) Does smoking invalidate the fast?
(b) Does injection nullify the fast?
بسم الله الرحمن الرحیم
(a) Inhaling smoke intentionally invalidates the fast (Radd al-Muḥṭār, 2: 395). Thus, smoking invalidates the fast. However, smoke patches do not nullify the fast, as it does not involve any inhalation.
(b) Injecting in the body directly into the bloodstream does not nullify the fast, as the jurists have conditioned passage through the brain or the jawf (the cavity of consequence) for the nullification of the fast (al-Baḥr al-Rāʾiq, 2: 299; Radd al-Muḥtār, 2: 395-6; Fatāwā Maḥmūdiyya, 15: 179).
Allah knows best
27 Ṣafar 1428 / 16 March 2007