How do drugs know where to go in the body? A pharmaceutical scientist explains
Tom Anchordoquy, Professor of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus
While pills come in many shapes and sizes, they all eventually reach your bloodstream and travel throughout your body. Vadim Sazhniev/iStock via Getty Images
When you take aspirin for a headache, how does the aspirin know to travel to your head and alleviate the pain?
The short answer is, it doesn’t: Molecules can’t transport themselves through the body, and they don’t have control over where they eventually end up. But researchers can chemically modify drug molecules to make sure that they bind strongly to the places we want them and weakly to the places we don’t.
Pharmaceutical products contain more than just the active drug that directly affects the body. Medications also include “inactive ingredients,” or molecules that enhance the stability, absorption, flavor and other qualities that are critical to allowing the drug to do its job. For example, the aspirin you swallow also has ingredients that both prevent the tablet from fracturing during shipping and help it break apart in your body.
As a pharmaceutical scientist, I’ve been studying drug delivery for the past 30 years. That is, developing methods and designing nondrug components that help get a medication where it needs to go in the body. To better understand the thought process behind how different drugs are designed, let’s follow a drug from when it first enters the body to where it eventually ends up.
When you swallow a tablet, it will initially dissolve in your stomach and intestines before the drug molecules are absorbed into your bloodstream. Once in the blood, it can circulate throughout the body to access different organs and tissues.
Drug molecules affect the body by binding to different receptors on cells that can trigger a particular response. Even though drugs are designed to target specific receptors to produce a desired effect, it is impossible to keep them from continuing to circulate in the blood and binding to nontarget sites that potentially cause unwanted side effects.
Many factors, like your age, genetics and diet, can affect how well your body processes a drug.
Drug molecules circulating in the blood also degrade over time and eventually leave the body in your urine. A classic example is the strong smell your urine might have after you eat asparagus because of how quickly your kidney clears asparagusic acid. Similarly, multivitamins typically contain riboflavin, or vitamin B2, which causes your urine to turn bright yellow when it is cleared. Because how efficiently drug molecules can cross the intestinal lining can vary depending on the drug’s chemical properties, some of the drugs you swallow never get absorbed and are removed in your feces.
Because not all of the drug is absorbed, this is why some medications, like those used to treat high blood pressure and allergies, are taken repeatedly to replace eliminated drug molecules and maintain a high enough level of drug in the blood to sustain its effects on the body.
Getting drugs to the right place
Compared with pills and tablets, a more efficient way of getting a drug into the blood is to inject it directly into a vein. This way, all the drug gets circulated throughout the body and avoids degradation in the stomach.
Many drugs that are given intravenously are “biologics” or “biotechnology drugs,” which include substances derived from other organisms. The most common of these are a type of cancer drug called monoclonal antibodies, proteins that bind to and kill tumor cells. These drugs are injected directly into a vein because your stomach can’t tell the difference between digesting a therapeutic protein and digesting the proteins in a cheeseburger.
In other cases, drugs that need very high concentrations to be effective, such as antibiotics for severe infections, can be delivered only through infusion. While increasing drug concentration can help make sure enough molecules are binding to the correct sites to have a therapeutic effect, it also increases binding to nontarget sites and the risk of side effects.
One way to get a high drug concentration in the right location is to apply the drug right where it’s needed, like rubbing an ointment onto a skin rash or using eyedrops for allergies. While some drug molecules will eventually get absorbed into the bloodstream, they will be diluted enough that the amount of drug that reaches other sites is very low and unlikely to cause side effects. Similarly, an inhaler delivers the drug directly to the lungs and avoids affecting the rest of the body.
Patient compliance
Finally, a key aspect in all drug design is to simply get patients to take medications in the right amounts at the right time.
Because remembering to take a drug several times a day is difficult for many people, researchers try to design drug formulations so they need to be taken only once a day or less.
Taking medications as instructed can help increase their effectiveness and reduce the risk of side effects. violetphoto/Moment via Getty Images
Similarly, pills, inhalers or nasal sprays are more convenient than an infusion that requires traveling to a clinic for a trained clinician to inject it into your arm. The less troublesome and expensive it is to administer a drug, the more likely it is that patients will take their medication when they need it. However, sometimes infusions or injections are the only effective way that certain drugs can be administered.
Even with all the science that goes into understanding a disease well enough to develop an effective drug, it is often up to the patient to make it all work as designed.
Tom Anchordoquy receives funding from the National Institutes of Health.
This article is republished from The Conversation under a Creative Commons license.
How do drugs know where to go in the body? A pharmaceutical scientist explains
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The Substance Abuse and Mental Health Services Administration, or SAMHSA, reported that among the people who misused prescription pain relievers in 2020, nearly 65% stated that their primary reason for doing so was to relieve physical pain. The percentage of people reporting drug misuse as a reason to get high was 11.3%.
Misuse is defined as patients taking prescription medications in a way other than what has been recommended by their doctor. It might look like taking someone else’s prescription or taking one’s own at larger or more frequent doses, or for a longer period of time.
Citing data from SAMHSA, Zinnia Health identified the most commonly misused prescription drugs in the United States, all of which are opioid analgesics, or opioid pain relievers. This class of drugs acts on the central nervous system by blocking pain signals to the brain. In addition to pain relief, these drugs also intensely trigger the brain’s reward centers, releasing endorphins and creating positive feelings commonly referred to as euphoria. This is what makes prescription opioids—and all opioids, for that matter—so dangerously addictive.
Prolonged use of opioids can increase a patient's tolerance to a particular drug. With higher tolerance, the drug becomes less effective, and patients won't experience the same level of pain relief and feelings of euphoria, which often leads people to seek out opioids with higher potency. This could be why such a large percentage of people reported misusing prescription opioids to relieve pain. For example, a person who has misused and developed a tolerance to morphine may seek out something stronger like oxycodone or hydromorphone, the effects of which are felt more quickly and more intensely.
SAMHSA also found that nearly half of people who misused pain relievers (47.2%) reported getting these drugs from a friend or relative—by stealing, buying, or receiving them for free. Roughly 44% of people reported getting prescriptions from a healthcare provider. Drug diversion—or the disruption of a prescription drug along its legal and intended path from manufacturer to doctor to patient—is a contributing factor in drug misuse. Diversion happens through doctor shopping, theft, and forgery, among others.
The United States is in its third wave of an opioid crisis, but it is important to note this current wave is characterized by illicitly produced synthetic opioids. Overdose deaths from commonly prescribed opioids have been on the decline over the last several years. However, knowing the uses and risks associated with these drugs can be life-saving. Read on to learn the most commonly misused prescription drugs in the United States.
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The Substance Abuse and Mental Health Services Administration, or SAMHSA, reported that among the people who misused prescription pain relievers in 2020, nearly 65% stated that their primary reason for doing so was to relieve physical pain. The percentage of people reporting drug misuse as a reason to get high was 11.3%.
Misuse is defined as patients taking prescription medications in a way other than what has been recommended by their doctor. It might look like taking someone else’s prescription or taking one’s own at larger or more frequent doses, or for a longer period of time.
Citing data from SAMHSA, Zinnia Health identified the most commonly misused prescription drugs in the United States, all of which are opioid analgesics, or opioid pain relievers. This class of drugs acts on the central nervous system by blocking pain signals to the brain. In addition to pain relief, these drugs also intensely trigger the brain’s reward centers, releasing endorphins and creating positive feelings commonly referred to as euphoria. This is what makes prescription opioids—and all opioids, for that matter—so dangerously addictive.
Prolonged use of opioids can increase a patient's tolerance to a particular drug. With higher tolerance, the drug becomes less effective, and patients won't experience the same level of pain relief and feelings of euphoria, which often leads people to seek out opioids with higher potency. This could be why such a large percentage of people reported misusing prescription opioids to relieve pain. For example, a person who has misused and developed a tolerance to morphine may seek out something stronger like oxycodone or hydromorphone, the effects of which are felt more quickly and more intensely.
SAMHSA also found that nearly half of people who misused pain relievers (47.2%) reported getting these drugs from a friend or relative—by stealing, buying, or receiving them for free. Roughly 44% of people reported getting prescriptions from a healthcare provider. Drug diversion—or the disruption of a prescription drug along its legal and intended path from manufacturer to doctor to patient—is a contributing factor in drug misuse. Diversion happens through doctor shopping, theft, and forgery, among others.
The United States is in its third wave of an opioid crisis, but it is important to note this current wave is characterized by illicitly produced synthetic opioids. Overdose deaths from commonly prescribed opioids have been on the decline over the last several years. However, knowing the uses and risks associated with these drugs can be life-saving. Read on to learn the most commonly misused prescription drugs in the United States.
How do drugs know where to go in the body? A pharmaceutical scientist explains
MedStock Photos // Shutterstock
- Misuse over the past year (previous users): 8.9%
- Misuse over the past year (general population): 0.2%
Known by its brand names Avinza or Kadian, morphine is an opioid used to treat both acute and chronic pain. While morphine can be administered intravenously, it is most commonly taken via tablet or capsule. Morphine is closely related to other analgesics like hydrocodone and oxycodone. The potency of other opioids is often determined or compared relative to morphine’s potency.
MedStock Photos // Shutterstock
- Misuse over the past year (previous users): 8.9%
- Misuse over the past year (general population): 0.2%
Known by its brand names Avinza or Kadian, morphine is an opioid used to treat both acute and chronic pain. While morphine can be administered intravenously, it is most commonly taken via tablet or capsule. Morphine is closely related to other analgesics like hydrocodone and oxycodone. The potency of other opioids is often determined or compared relative to morphine’s potency.
How do drugs know where to go in the body? A pharmaceutical scientist explains
chatuphot // Shutterstock
- Misuse over the past year (previous users): 9.0%
- Misuse over the past year (general population): 0.5%
Tramadol, commonly referred to by its brand name Ultram, is a synthetic opioid used to treat moderate to severe pain, typically following a surgery. The drug is commonly prescribed as extended-release tablets to help with chronic severe pain from conditions like fibromyalgia. In 2019, an estimated 5.5 million people were prescribed Tramadol, totaling nearly 20 million prescriptions. It was the 35th most prescribed drug in the U.S.
chatuphot // Shutterstock
- Misuse over the past year (previous users): 9.0%
- Misuse over the past year (general population): 0.5%
Tramadol, commonly referred to by its brand name Ultram, is a synthetic opioid used to treat moderate to severe pain, typically following a surgery. The drug is commonly prescribed as extended-release tablets to help with chronic severe pain from conditions like fibromyalgia. In 2019, an estimated 5.5 million people were prescribed Tramadol, totaling nearly 20 million prescriptions. It was the 35th most prescribed drug in the U.S.
How do drugs know where to go in the body? A pharmaceutical scientist explains
Joe Mamer // Shutterstock
- Misuse over the past year (previous users): 12.2%
- Misuse over the past year (general population): 0.9%
Codeine is an opioid used to treat mild to moderate pain and is most often prescribed as a cough suppressant. It can also be used to treat gastrointestinal problems like diarrhea. Because codeine is milder than other opioids, users with intentions of misuse increase dosages to achieve a greater high. Misuse of codeine can lead to the misuse of more intense opioids.
Joe Mamer // Shutterstock
- Misuse over the past year (previous users): 12.2%
- Misuse over the past year (general population): 0.9%
Codeine is an opioid used to treat mild to moderate pain and is most often prescribed as a cough suppressant. It can also be used to treat gastrointestinal problems like diarrhea. Because codeine is milder than other opioids, users with intentions of misuse increase dosages to achieve a greater high. Misuse of codeine can lead to the misuse of more intense opioids.
How do drugs know where to go in the body? A pharmaceutical scientist explains
Canva
- Misuse over the past year (previous users): 12.6%
- Misuse over the past year (general population): 1.7%
Hydrocodone is the most frequently prescribed opioid in the U.S. In 2020, 4.7 million people misused hydrocodone products, making them the most commonly misused type of prescription pain reliever that year. Hydrocodone, also known by its brand name Vicodin, is given to patients with moderate to severe pain usually following surgery or injury, or to alleviate pain associated with medical conditions such as cancer. In combination with homatropine, hydrocodone can also be used as a cough suppressant. Unlike other opioids, hydrocodone is not often illicitly manufactured and the vast majority of misused hydrocodone is pharmaceutical.
Canva
- Misuse over the past year (previous users): 12.6%
- Misuse over the past year (general population): 1.7%
Hydrocodone is the most frequently prescribed opioid in the U.S. In 2020, 4.7 million people misused hydrocodone products, making them the most commonly misused type of prescription pain reliever that year. Hydrocodone, also known by its brand name Vicodin, is given to patients with moderate to severe pain usually following surgery or injury, or to alleviate pain associated with medical conditions such as cancer. In combination with homatropine, hydrocodone can also be used as a cough suppressant. Unlike other opioids, hydrocodone is not often illicitly manufactured and the vast majority of misused hydrocodone is pharmaceutical.
How do drugs know where to go in the body? A pharmaceutical scientist explains
Canva
- Misuse over the past year (previous users): 14.5%
- Misuse over the past year (general population): 1.1%
Oxycodone is an opioid prescribed to treat ongoing severe pain. OxyContin and Percocet are two of the most recognizable brands, with the former being a pure form of oxycodone and the latter a combination of oxycodone and aspirin. Roughly 3.2 million people misused oxycodone products in 2020, making it the second-most commonly misused pain reliever behind hydrocodone. Oxycodone misuse is prevalent across the spectrum of geographic, demographic, and socioeconomic conditions.
Canva
- Misuse over the past year (previous users): 14.5%
- Misuse over the past year (general population): 1.1%
Oxycodone is an opioid prescribed to treat ongoing severe pain. OxyContin and Percocet are two of the most recognizable brands, with the former being a pure form of oxycodone and the latter a combination of oxycodone and aspirin. Roughly 3.2 million people misused oxycodone products in 2020, making it the second-most commonly misused pain reliever behind hydrocodone. Oxycodone misuse is prevalent across the spectrum of geographic, demographic, and socioeconomic conditions.
How do drugs know where to go in the body? A pharmaceutical scientist explains
PureRadiancePhoto // Shutterstock
- Misuse over the past year (previous users): 14.8%
- Misuse over the past year (general population): 0.1%
Pharmaceutical fentanyl, which this data refers to, can be up to 100 times more potent than morphine and is most often used to treat pain associated with advanced cancer. Legally produced fentanyl is typically administered through patches or lozenges. According to the Drug Enforcement Administration, misuse of these products can include ingesting the gel inside the patches or freezing the patches, cutting them into pieces, and placing them inside the cheek to absorb the contents. Because a percentage of fentanyl remains in used patches even after a three-day use, used patches are also targeted for misuse. Illegally manufactured, nonpharmaceutical fentanyl is at the heart of the third and current wave of America’s opioid epidemic.
PureRadiancePhoto // Shutterstock
- Misuse over the past year (previous users): 14.8%
- Misuse over the past year (general population): 0.1%
Pharmaceutical fentanyl, which this data refers to, can be up to 100 times more potent than morphine and is most often used to treat pain associated with advanced cancer. Legally produced fentanyl is typically administered through patches or lozenges. According to the Drug Enforcement Administration, misuse of these products can include ingesting the gel inside the patches or freezing the patches, cutting them into pieces, and placing them inside the cheek to absorb the contents. Because a percentage of fentanyl remains in used patches even after a three-day use, used patches are also targeted for misuse. Illegally manufactured, nonpharmaceutical fentanyl is at the heart of the third and current wave of America’s opioid epidemic.
How do drugs know where to go in the body? A pharmaceutical scientist explains
Canva
- Misuse over the past year (previous users): 16.6%
- Misuse over the past year (general population): 0.1%
Hydromorphone, commonly referred to by brand names Dilaudid or Exalgo, is an opioid prescribed to treat severe pain in patients who are resistant to less potent opioids. It is roughly eight times stronger than morphine, and the effects of a 1-2mg dose can be felt in as little as 15 minutes. Hydromorphone carries a high risk of addiction and is prescribed only in certain medical circumstances, like managing pain from cancer or cancer-related treatment. According to the Drug Enforcement Administration, hydromorphone used to be the most commonly misused or diverted drug, now supplanted by oxycodone and hydrocodone.
Canva
- Misuse over the past year (previous users): 16.6%
- Misuse over the past year (general population): 0.1%
Hydromorphone, commonly referred to by brand names Dilaudid or Exalgo, is an opioid prescribed to treat severe pain in patients who are resistant to less potent opioids. It is roughly eight times stronger than morphine, and the effects of a 1-2mg dose can be felt in as little as 15 minutes. Hydromorphone carries a high risk of addiction and is prescribed only in certain medical circumstances, like managing pain from cancer or cancer-related treatment. According to the Drug Enforcement Administration, hydromorphone used to be the most commonly misused or diverted drug, now supplanted by oxycodone and hydrocodone.
How do drugs know where to go in the body? A pharmaceutical scientist explains
PureRadiancePhoto // Shutterstock
- Misuse over the past year (previous users): 26.5%
- Misuse over the past year (general population): 0.2%
Buprenorphine is an opioid used in the medication-assisted treatment of opioid use disorder, or OUD, particularly to reduce intense withdrawal symptoms that can lead to relapse. It works by stimulating the brain in the same way as heroin or methadone, but to a lesser degree, creating a limit to its effects. It can produce euphoria without the risk of suppressing breathing, which is the actual cause of death in opioid overdoses. Since prolonged opioid use inhibits the brain’s ability to produce dopamine on its own, the right dosage of buprenorphine and a comprehensive treatment plan allows OUD patients to feel “normal” or at equilibrium.
This story originally appeared on Zinnia Health and was produced and distributed in partnership with Stacker Studio.
PureRadiancePhoto // Shutterstock
- Misuse over the past year (previous users): 26.5%
- Misuse over the past year (general population): 0.2%
Buprenorphine is an opioid used in the medication-assisted treatment of opioid use disorder, or OUD, particularly to reduce intense withdrawal symptoms that can lead to relapse. It works by stimulating the brain in the same way as heroin or methadone, but to a lesser degree, creating a limit to its effects. It can produce euphoria without the risk of suppressing breathing, which is the actual cause of death in opioid overdoses. Since prolonged opioid use inhibits the brain’s ability to produce dopamine on its own, the right dosage of buprenorphine and a comprehensive treatment plan allows OUD patients to feel “normal” or at equilibrium.
This story originally appeared on Zinnia Health and was produced and distributed in partnership with Stacker Studio.
While pills come in many shapes and sizes, they all eventually reach your bloodstream and travel throughout your body. Vadim Sazhniev/iStock via Getty Images
Drugs aren’t sentient, but good design can help them get where doctors and patients want them to go. Andersen Ross/DigitalVision via Getty Images
Sometimes the most effective way to deliver a drug is through an infusion. gorodenkoff/iStock via Getty Images
Taking medications as instructed can help increase their effectiveness and reduce the risk of side effects. violetphoto/Moment via Getty Images
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