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Medications that require a prescription are called legend drugs. These all have a written legend (or caption) on the package stating, “CAUTION: Federal Law prohibits dispensing without a prescription.” Radiopaque contrast agents and other medications administered in the radiology department fall into the category of legend drugs. The imaging technologist must therefore know what constitutes a legal prescription before dispensing or administering drugs or diagnostic agents ordered.
A valid prescription or order for a drug includes at least the following seven components:
1.Patient name, room number or address, and identification numbers
2.Drug name (generic or brand)
3.Dosage (in proper units of measure for particular drug)
4.Dosage form (e.g., tablet, injection, solution)
5.Route of administration (e.g., oral, parenteral, rectal)
6.Date order is written
For a drug to produce pharmacologic effects in the body, it must first reach the site of action. The process required for a drug to reach the site of action is best described using biopharmaceutic and pharmacokinetic principles.
Biopharmaceutics is the area of pharmacology that focuses on the method for achieving effective drug administration. Drugs are placed into vehicles by the manufacturing process. A drug vehicle is a substance into which a drug is compounded for initial delivery into the body. A dosage form—solid, liquid, gas, or any combination of these—is the combination of both the drug and the vehicle used to deliver the drug. A dosage form must be capable of releasing its contents so that the drug can be delivered to the site of action.
•Buccal or sublingual tablets, such as nitroglycerin, are designed to disintegrate in the buccal or sublingual space and become absorbed through the buccal or sublingual vasculature
Troches are generally in the form of or pastilles. These are solids that contain medicine in a hard sugar or glycerinated gelatin base designed to dissolve slowly in the mouth. Topical oral antifungals and anesthetics are most often placed in this dosage form so that continued contact will be made between the medication and the oral mucosa.
Compressed suppositories or inserts are solid dosage forms generally designed for vaginal or rectal delivery. On contact with the mucosa and in the presence of body temperature, these dosage forms melt away to release the medicinal agent.
Abraham Lincoln's mother died when the family dairy cow ate poisonous mushrooms and Mrs. Lincoln drank the milk.
Medication is absorbed in either liquid or gaseous solution. Therefore, any solid or semisolid drug must first enter into one of these solution forms before becoming absorbed across a cellular membrane. A medication in solid form will generally require more time to enter the body than the same medication in liquid form. Disintegration and dissolution are generally considered to constitute the beginning of the pharmacokinetic process.
Prior to systemic action, a drug must either undergo the absorption process or be administered by direct intravenous injection, thus bypassing the need for absorption. Numerous anatomic sites, including GI tract, lungs, mucous membranes, eyes, skin, muscle, and subcutaneous tissues, can be used for systemic drug absorption.
Some analgesic formulas, such as Alka-Seltzer and Bromo-Seltzer, are liquid (disintegrated) when they enter the body. This does shorten the time between administration and onset of action (pain relief).
A large amount of blood supplies these sites. Blood must be flowing to the absorbing surface during the absorptive process to allow entry into the systemic circulation. Altered blood flow, such as occurs in cardiovascular shock, may change the drug absorption profile. Consequently, a patient who is in shock generally requires medication delivered through the intravenous route.
Once a drug is absorbed into the bloodstream, it is immediately distributed throughout the body by the circulation of the blood. Distribution is defined as the transport of a drug in body fluids from the bloodstream to various tissues of the body and ultimately to its site of action.
Several factors affect distribution, as follows:
1.Cardiac output: amount of blood pumped by the heart per minute.
2.Regional blood flow: amount of blood supplied to a specific organ or tissue.
3.Drug reservoirs: drug accumulations that are bound to specific sites, such as plasma, fat tissue, and bone tissue
Drug molecules, whether they are intact or metabolized, eventually must be removed from the body. This elimination is primarily accomplished by the kidneys. They filter the blood and remove unbound, water-soluble compounds. This is one reason why drug testing is often done on urine.
The intestines may also eliminate drug compounds. After metabolism by the liver, a metabolite may be secreted into the bile, passed into the duodenum, and eliminated in the feces.
The third mechanism of excretion is the respiratory system. Gases or volatile liquids that are administered through the respiratory system usually are eliminated by the same route.
Breast milk, sweat, and saliva also contain certain drug compounds but are not the body's predominant mechanisms for elimination
Antiarrhythmic (or antidysrhythmic) medications are those drugs that affect the electrical conduction system of the myocardium. The actions of these medications differ among the individual drugs.
The ultimate goal for this class of medications is to suppress excess electrical conduction within the cardiac system and thus decrease arrhythmia (dysrhythmia) production
Antihypertensive medications assist in lowering the blood pressure to safe, long-term goals. These drugs also affect heart failure in a positive way by decreasing the pressure against which the heart must pump. This allows the failing heart to pump more efficiently without “tiring out.” Many studies are now confirming the positive long-term effects that some antihypertensives have on the duration of life.
The first known heart medicine was discovered in an English garden. In 1799, physician John Ferriar noted the effect of dried leaves of the common foxglove plant, Digitalis purpurea, on heart action. Still used in heart medications, digitalis slows the pulse and increases the force of heart contractions and the amount of blood pumped per heartbeat.
For computed tomography (CT) or digital subtraction angiography (DSA), the serum iodine concentration needs only to be between 2 and 8 mg/ml. Thus, either a less concentrated iodine contrast medium or a slower intravascular infusion will produce adequate pharmacodynamic action for these imaging procedures.
Patients receiving any of the anticoagulant, antiplatelet, or thrombolytic medications are at risk for bleeding. In some cases, such as with the thrombolytics, severe bleeding can to lead to hemorrhagic stroke. Therefore, the imaging technologist should know about the signs and symptoms of an evolving stroke so that it can be reported quickly if patients are taking one of these medications
Antiplatelet medication is generally used in patients who have experienced an acute ischemic event to either their heart or their brain in the past. Since platelets are one of the initial instigators of blood clot formation, cardiologists and neurologists will prescribe antiplatelet drugs to prevent that portion of the coagulation cascade. Aspirin is one of the most common oral medications for inhibiting platelet effects.
Thrombolytic medication is used to actively break up a newly formed clot, such as found in patients with acute myocardial infarction, acute stroke secondary to blood clot, or lower leg ischemia. Alteplase, retaplase, streptokinase, tenecteplase, and urokinase are the most frequently used medications in this class. If a patient has recently been given an agent in this class, the patient is at very high risk for bleeding internally and externally. Use caution with all intravenous (IV) sites. Do not start an IV line in these patients without physician orders and close supervision.
Analgesic medications are prescribed more frequently than any other medication on the market. The drugs are used to treat both acute and chronic pain syndromes, such as arthritis, headache, muscle sprains, cancer pain, surgical and traumatic pain, nerve pain, and in some cases, anxiety.
Narcotic medications stimulate central nervous system receptors known as opioid receptors and cause a decrease in the perception of pain. These are very potent analgesics and are associated with the potential for physical and psychological addiction. The narcotic class of analgesic is generally highly controlled by the local and federal enforcement agencies to prevent misappropriation into the community. The narcotics are also dangerous in that respiratory depression can rapidly occur to the point of respiratory arrest if the dose is too great. The technologist should keep this concept in mind if patients are being treated with narcotic medications. If respiratory arrest occurs, naloxone is the drug of choice (given intravenously, intramuscularly, or endotracheally) to reverse immediately the respiratory depressant effects of narcotic agents. Examples of common narcotic medications include morphine
Acetaminophen is probably the most common analgesic in use today. It is contained in almost all pain medication combinations and is in a subclass by itself. It is not fully known just how acetaminophen elicits its effects, but some believe that it acts by inhibiting prostaglandins in the central nervous system that are responsible for pain production. Acetaminophen is a low-potency pain reliever and must not exceed 4000 mg per day because it is associated with severe liver damage at high doses. Long-term use of high doses can also cause renal and cardiac damage.
Antihistamines are medications used to block histamine from producing adverse effects such as itching, inflammation, respiratory distress, and overall allergic reactions. Common antihistamines include hydroxyzine (Vistaril, Atarax) and diphenhydramine (Benadryl).
Diabetes and hypothyroidism are two common endocrine problems for which patients frequently receive drug treatment.
Antidiabetic medication is required for patients who have difficulty maintaining proper balance between blood sugar and tissue sugar. Some patients are termed insulin dependent (diabetes mellitus type 1) because they have little or no circulating endogenous insulin. Diabetic patients who have sufficient circulating endogenous insulin but poor receptor sensitivity to the insulin are termed non–insulin dependent (diabetes mellitus type 2).
Technologists need to always be aware of patients receiving metformin because this drug should be held before and for at least 48 hours after receiving a radiopaque contrast agent. If metformin is not held, the patient is put at increased risk for severe metabolic acidosis secondary to metformin metabolite accumulation, in the event renal dysfunction is caused by the radiopaque contrast agent.
Antibiotics are therapeutic agents used to kill or suppress pathologic microorganisms responsible for causing infectious diseases. Antifungals are agents used to kill mycotic (fungal) organisms, and antivirals are used to suppress and limit the spread or shedding of viruses that invade the human body. Generally, these three medication subclasses act at the cellular level to destroy, inhibit, or suppress the cell wall, enzymatic activity, or ribosomal or deoxyribonucleic acid (DNA) function of an invading microorganism.
Chemotherapy drugs are extremely toxic compounds designed to kill off rapidly growing (e.g., cancerous) cells of the human body by altering or destroying the various stages in cellular division. These agents are toxic to all cells that are in a growth stage, not only cancerous cells. Special precautions should be taken with all chemotherapy patients so that no medication touches the unexposed skin of a health care worker. Coming into physical contact with these medications can put the health care worker at risk of serious side effects, including the stimulation of a cancerous condition. Even coming into contact with bodily fluids into which the chemotherapy is secreted, such as urine, can pose a potential threat to the clinician. Universal precautions and special gloves and gowns should be worn when dealing with chemotherapy.
The rosy periwinkle plant, found in Madagascar, is used to cure leukemia
Radiopaque contrast media (ROCM) are high-density pharmacologic agents used to visualize low-contrast tissues in the body, such as the vasculature, kidneys, gastrointestinal (GI) tract, and biliary tree.
The most frequently prescribed ROCM are iodine and barium. The atomic number of iodine is 53, and the atomic number of barium is 56. Each has a much higher atomic number and mass density than the low-contrast tissues listed above. When an iodinated compound fills a blood vessel or when barium fills a portion of the GI tract, these internal organs become visible on a radiograph. Low-kilovoltage techniques (below 80 kilovoltage peak [kVp]) are usually selected to produce high-contrast radiographs of the blood vessels or genitourinary tract. Higher-kilovoltage operation (above 90 kVp) is used in GI examinations not only to reveal the presence of the organ, but also to penetrate the contrast media to see the walls and inner structures.
Serious adverse effects from ROCM do occur. An estimated one of every 20,000 to 40,000 patients receiving ROCM dies as a result of these effects. Although the odds of death appear low, they become very real if it happens to you or your patient. Thus, it is paramount that the technologist understand adverse effects so that proper actions can be instituted as rapidly as possible.
Iodine molecules contained within ROCM are effective photon absorbers in the human body. The iodine molecules essentially do not allow as many photons to pass through for projection onto the radiographic film. Thus, iodine molecules are responsible for the silhouette images projected. Radiopacity elicited by ROCM is a direct function of the percentage of iodine (except in the case of barium sulfate) in the molecule and the concentration of media present. In the case of barium sulfate, barium acts as iodine.
Intravascular (i.e., intravenous or intraarterial) ROCM are used to add density to vascular structures. Increased density of the media alters the attenuation of x-rays passing through the area, thus enhancing the anatomic image on the radiographic film.
Three broad categories of intravascular ROCM exist: high-osmolality ionic, low-osmolality nonionic, and low-osmolality ionic ROCM. Generally, ionic ROCM exist in salt forms consisting of sodium and meglumine whereas nonionic ROCM are supplied as nonsalt forms.
High-osmolality ionic ROCM,contain three iodine atoms per molecule and dissociate into two osmotically active particles when injected into the bloodstream. These particles consist of one radiopaque anion (negatively charged particle) and one cation (positively charged particle) for every three iodine atoms in solution.
The newer low-osmolality nonionic ROCM, contain three iodine atoms per molecule and do not dissociate in solution
Intravascular ROCM are excreted primarily via the kidneys; they are concentrated in the kidneys and subsequently opacify the entire renal system. Generally, renal parenchyma is opacified first, followed by the tubular structures, renal calyces, and pelvis, and ending with the ureter and bladder. In normal renal function, up to 100% of an intravascular dose is excreted in 24 hours. A very small percentage may be excreted into the intestines through the hepatic-biliary system. Several days may be required for complete excretion in patients with renal impairment. Consequently, these patients have much lower to no opacification in the kidneys because up to 50% of the ROCM may be eliminated via the hepatic-biliary system, thus opacifying the biliary and GI tracts.
Enteral ROCM are used to diagnose and evaluate disorders of the GI system. These agents may also be used to help define the cardiac shadow. Enteral ROCM can be broken down into the categories of aqueous solutions, suspensions, and tablets.
Diatrizoate meglumine and diatrizoate sodium solutions are used for oral or rectal administration to aid in the diagnosis of GI tract disorders. Generally, these solutions are used when barium sulfate suspension is potentially harmful, such as in GI perforation. The high osmolality of these agents causes significant osmotic action within the GI tract. This leads to significant dilution of the iodine as well as a profuse diarrhea, systemic hypovolemia, dehydration, and electrolyte imbalance. Iodine dilution leads to less definitive diagnostic studies; this, along with the adverse effect profile of iodine, is why barium sulfate is often the preferred diagnostic GI agent. The diatrizoate compounds are preferred over barium sulfate for CT because of less artifact production.
Radiodensity (radiopacity) occurs immediately in the esophagus and stomach after oral administration but may take 15 to 90 minutes for the duodenum. Immediate radiodensity occurs in the rectum and colon following rectal administration.
Gastrointestinal ROCM are not absorbed through the GI wall and are thus distributed solely into the GI lumen. These agents are excreted by the GI tract into the feces.
Barium sulfate is an ROCM suspension used for oral or rectal administration to aid in the diagnosis of GI tract disorders. Barium is radiodense in the same manner as iodine. Radiodensity occurs immediately in the esophagus and stomach after oral administration but may take 15 to 90 minutes for the duodenum. Immediate radiodensity occurs in the rectum and colon following rectal administration.
Barium sulfate is generally the preferred GI ROCM because it provides a more thorough visualization of structures, especially the mucosa, without extensive local adverse effects. Barium sulfate may produce significant artifact in CT evaluation of the GI tract and thus is not the preferred agent for this radiologic examination.
Barium sulfate is not absorbed through the GI wall and thus is distributed solely into the GI lumen. It is excreted by the GI tract into the feces.
Iocetamic acid (Cholebrine) is an oral ROCM used for opacifying the gallbladder. Absorption varies from person to person, but the gallbladder can generally be visualized approximately 10 to 15 hours after oral administration
Most of the iocetamic acid is excreted into the urine 48 hours after administration. Some is excreted via the biliary system into the feces.