The Patient Was…

Most of us are familiar and experienced with taking medications of one sort or another. Far and away, the most common form of drug administration is via the oral route, that is, by swallowing either pills or liquid medicines. We are also mostly accustomed to “getting a shot.” These injections are usually delivered into a fairly large muscle like the deltoid in the upper arm or the gluteus in the buttocks.

But the human body, in its complexity, offers several other possible routes of administering drugs. These may become important in a variety of clinical situations. And some may surprise you.

Swallowing pills and liquids is, once again, the most usual and perhaps most natural way for us to get medications into us. After all, we eat and drink as part of our very existence and it is second nature to us.

But what actually happens when a medication is swallowed?

The medicine travels down the esophagus, the muscular tube connecting the throat and the stomach. In the stomach, the medicine is acted upon by stomach acid and various enzymes. Tablets and capsules begin to disintegrate and the medication dissolves into the stomach liquids.

The stomach contents empty into the small intestine where the medication is absorbed through the intestinal wall into the blood stream. It travels through a venous (vein) system called the hepatic portal vein and enters the liver. The liver is an extremely active metabolic center, where various enzymes act on the medication to prepare it for its function in the body and for its eventual elimination through the kidneys or the bowel.

From the liver, the medication enters the general blood circulation, where it travels around the body until it reaches its site of action where it exerts its effects by reacting with specialized receptors in the tissues it is designed for. It is notable that a drug may interact with other organs as well as the particular one it is supposed to affect, and this may result in some unwanted and perhaps unexpected medication side effects.

So, when you swallow your medicine, you are actually initiating a complicated sequence of events involving many parts of your body and many complex processes.

Certain medicines are not available for oral administration. The reasons are several, including the nature of the drug molecules themselves, and manufacturing limitations. Also, the clinical situation may not lend itself to ingesting a drug by mouth. One example could be an unconscious individual; another might be a patient unable to swallow easily. Faster speed of drug effect might be yet another reason for bypassing the oral route. Fortunately, other routes of getting medications into patients are available.

Injections are familiar to all of us. There are basically four types. Intramuscular injections are perhaps the most familiar and, as described earlier, the needle is usually inserted into a fairly large muscle where blood vessels are abundant to absorb the drug and circulate it. The upper arm deltoid muscle and the gluteus muscles of the buttocks are customary sites of injection.

Subcutaneous injections are fairly routine, as well. Here, a short needle is inserted into the fatty tissue just beneath the skin and not far enough to reach deeper muscle and other tissues. Subcutaneous injection usually results in slower, more sustained absorption of medication. The abdominal wall and the thigh are common sites of subcutaneous injections. One of the common medications administered this way is insulin, used by patients with diabetes.

A third and well recognized route of injecting drugs is by intravenous (IV) administration. A needle is inserted directly into a vein, and medicine is either given in a single push, called a bolus, or administered more slowly over time as a so-called infusion or IV drip. Hospitalized patients often have intravenous drips running with simple saline (salt water) or dextrose (sugar) solutions to keep access to the venous system available for intermittent administration of active drugs.

A fourth type of injection, familiar to many patients, is an injection directly into a local site of injury or inflammation. Common examples of this are cortisone injections into painful joints and anesthetic injections into deeper tissues in preparation for a biopsy or other locally invasive procedure.

While the oral and injectable routes of administering drugs are the most common ways of giving medicine, there are several other less frequently employed methods. Transdermal or through-the-skin drug administration is a fairly frequently used technique. The medication is usually embedded in a patch that is then applied to the skin. The drug slowly penetrates through the most-resistant, outer skin layer into the tissues below, where thin-walled blood vessels called capillaries absorb the medication into the circulatory system.

Medicine-containing patches are usually applied to skin areas not visible under normal conditions; nobody has to know you’re wearing a patch. But visibility can become a problem if one goes to a gym, for example, and is fairly exposed in front of other people. One patient of mine, a divorced middle-aged woman, was delighted with a skin patch containing a heart medicine until, on a routine visit to my office, she unexpectedly complained bitterly about it. I didn’t understand her change in attitude until she confessed she had met a new man and planned to become intimate with him; and, in her words, “I’ll be damned if I’ll let him see I’m taking this medicine.”   

To overcome situations like that, a multinational U.S. – based conglomerate, famous for adhesives, developed a colorless medication patch that was virtually invisible on the skin. When I discussed this in a television interview with a skeptical reporter, she insisted that there couldn’t be a patch so inconspicuous and that I hadn’t convinced her. When I saw there were only a few seconds remaining on the clock in the studio, I pointed to the back of my hand that I had waved in front of her all during the interview and pointed to a dummy patch (not containing medicine) I had worn the whole time. The camera focused on her slack-jawed face as the interview ended.

The final method of drug administration involves a process called transmucosal drug delivery, or delivery through what are called mucus membranes. Mucus membranes are thin layers of tissue that line most body cavities, including the nose and mouth, throat, and even the vagina and rectum. These tissue layers contain many thin-walled capillary blood vessels that absorb the medications applied to the tissue. Advantages include speed of drug entrance into the blood circulation for transport around the body, and avoidance of the effects of passage through the intestinal tract and liver.

Cardiologists are very familiar with this route of drug administration, since nitroglycerine tablets, an essential medication for many heart patients, is typically placed under the tongue (sublingual) or in the buccal (cheek) cavity for quick absorption. Other medications, given under different circumstances and for different purposes, can be administered through the mucosal tissues (mucus membranes) of the nasal, vaginal and rectal cavities.

Medications are a critical part of medical care. It’s comforting to know, and fascinating as well, that when the typical and commonly used oral and injectable pathways for drug administration are impractical or unavailable, the complexity of the human body provides other means of access for medicines.