The most common reason one would not choose an oral route and would instead elect to use nasal or buccal routes is due to delays in onset of oral medications and due to gastric acid destruction and first pass metabolism of drug resulting in very low levels available to the blood stream. Failure to utilize the nose brain path also occurs with oral (and buccal) medications - resulting in much slower drug delivery to the brain. Interestingly, oral medications are also commonly refused by 30% of pediatric patients making them completely ineffective in this situation. Buccal medications also require a cooperative patient who will retain the medication within their buccal and sublingual mucosal areas and not swallow or spit it out. In fact, even when buccal medications are administered to volunteers in research settings, only about 56% remains in the oral cavity for absorption. Even nasal drug delivery can have problems depending on the delivery method. Yuen et al report that in % of pediatric patients they were unable to dispense drops into the nose due to resistance to this delivery technique. While nasal delivery is possible the majority of the time, to overcome these delivery issues a number of device have been developed that enhance delivery - these are discussed in the delivery techniques section of this web site.
Intravenous or intravascular laser blood irradiation (ILBI) involves the in-vivo illumination of the blood by feeding low level laser light generated by a 1–3 mW helium–neon laser at a wavelength of nm into a vascular channel, usually a vein in the forearm, under the assumption that any therapeutic effect will be circulated through the circulatory system .  Most often wavelengths of 365, 405, 525 and 635 nm and power of mW are used. The technique is widely used at present in Russia, less in Asia, and not extensively in other parts of the world. It is shown that ILBI improves blood flow and its transport activities, therefore, tissue trophism, has a positive effect on the immune system and cell metabolism.   This issue is subject to skepticism.  There have been some calls to increase research on this topic.