If you are exposed to liquids, including drugs – the pharmaceutical kind – introduced directly in your veins, the procedure is termed intravenous (within the vein) therapy. Because it does not have to take a long detour through the digestive system, which can also break down the drug, intravenous therapy ensures the drug gets to the target location faster and with less chances of disruption. Of course, IV therapy is the preserve of a medical professional, who knows how to avoid infection and, among other things, knows precisely where the vein is that the needles needs to be injected in to, in order to administer the IV. Among other things, the procedure can be used to provide blood or plasma to those who have lost blood or need to have it replaced, electrolytes for the dehydrated, and glucose to the hypoglycemic or those too exhausted to eat, or simply drugs to fight certain infections. The drug can be injected using a syringe and hypodermic needle. The medical professional shuts off blood supply so that the veins, which are closer to the surface, bulge. Then they send in the hypodermic needle, pulling back the plunger of the syringe, thus drawing back blood. This confirms that the needle is within a vein.
To ensure steadier supply of chemicals, instead of a syringe, the needle leads back up from a peripheral vein – usually in an arm or leg – to ensure more regular supply of the drug in the form of a drip. Instead of leaving a needle in, nowadays a needle leads the way into the vein but is removed, leaving behind a softer catheter, which can be capped for re-use. Of course, the drug available reduces as it spreads out from the site. The alternative is intravenously infusing tissue close to the actual target site. As with any therapy, intravenous therapy has its problems. You risk infection, the veins getting scarred or it may prompt an immune response, or you may mess up the electrolytes in your body by putting in too little or too much. Again, a drug for your heart may be perusing your biceps or cardiac muscle and doing no good, you may be sending in more fluid than you can handle (remember, even water can poison you if you consume too much), or it may send in an air bubble or a blood clot up to cause a heart attack or a stroke. Well managed, though, intravenous therapy is a boon and used extensively in the medical community.