Many vaccines are one-time injections into a muscle. Many injected medications are administered through an intravenous line directly into the bloodstream for faster and more predictable dosing. Skin is another route of administration. Creams, salves, ointments, and gels long have been used to treat skin problems, but now dermal patches can be used for medication that must be absorbed throughout the body. Though patches are becoming increasingly popular for other drugs as well, it can take several days for medication administered by patch to reach a therapeutic blood level, and the exact blood level can be difficult to control.
Patches also tend to be an expensive way to administer a drug.
Asthma patients often use steroid inhalers. Inhaled drugs tend to affect only the respiratory tract, resulting in fewer side effects. Suppositories may be used when patients are unable to take medication by mouth or when a more localized effect is desired. Each route of administration has pros and cons for different patients taking different drugs. As technology changes, it's important to talk with your doctor about various options.