4.1 Routes of Administration
Research has shown that the faster a substance reaches the brain, the more likely it is to be misused. Different methods of delivery—smoking, injecting, or snorting—largely influence how quickly a substance reaches the brain. Delivery methods, genetics, and the environment all influence the potential of a Substance to cause addiction.
Delivery methods, genetics, and environment all influence the potential of a substance to develop into a substance use disorder.
Activities / Reflection:
- Create a list of all the different routes of administration that a person can get a substance/drug into their body?
- What influences the potential impact of the substance in their body?
- Rate your list; which do you think has the biggest impact? What way do you think is fastest or slowest? Why?
Lets watch a video on Methods of Drug Administration.
Methods of Drug Administration. by Professor Dave Explains. When a patient must be administered a drug in a medical setting, how does this occur? Well there are lots of ways. Pills or tablets can be ingested orally. There are topical creams, tubes, injections, and more. How does each one work, and why would one select that method over another? Let’s go through a summary of the methods of drug administration now! (1)
When a person injects a substance into their vein or smokes and inhales into their lungs, they feel the effects of the substance very quickly. Snorting a substance into a nasal cavity or swallowing a substance means it takes longer for the body to absorb and feel the effects; the drugs uptake is slower(2). People can take a substance in a number of different ways. The route of administration are described in the table below.(3)
| Method | Example of Drug | Time Needed for Effect | Advantages of Route | Disadvantages of Route |
| Oral | Alcohol | 30-60 minutes | Convenient | Slow, irregular |
| Inhalation | Nicotine | 8 seconds | Fast | Lung damage |
| Intravenous Injection | Heroin | 15 seconds | Fast | Overdose/ infections |
| Mucous membrane | Cocaine | 1-2 minutes | Convenient | Local tissue damage |
| Subcutaneous injection | Heroin | 5-10 minutes | Safer & easier than IV | Infection |
| Intramuscular Injection | Morphine | 10-15 minutes | Controlled | Painful |
| Transdermal | Nicotine | 15-20 minutes | Convenient | Limited application/ potential misuse |
The fastest way to get a substance to the brain is by smoking it. When a substance like tobacco smoke for instance is taken into the lungs, nicotine seeps into lung blood where it can quickly travel to the brain. This fast delivery is one reason smoking cigarettes is can turn into a disorder quickly.
Injecting directly into a blood vessel is the second fastest way to get a substance to the brain, followed by snorting or sniffing it through the nose. A slow mode of delivery is ingestion, such as drinking alcohol. The effects of alcohol take many minutes rather than a few seconds to cause behavioural and biological changes in the brain.
Rapid Delivery Changes Your Brain
People who have a substance use disorder often choose a delivery method that gets them higher quickly. As the SUD progresses, people will often seek out the more immediate and more intense high. But speed doesn’t seem to be the only reason that rapid delivery is an important factor. Recent evidence suggests that the mode of delivery can actually influence which part of the brain is most affected by a substance. Rapid delivery, such as smoking, affects brain regions that facilitate substance use disorders.
Slow Delivery: An Addiction Therapy?
Increased knowledge about substance delivery methods is leading to new therapies to support substance use disorders. It turns out that delivering a substance slowly, by ingestion or through the skin, produces a weaker, longer-lasting effect. Nicotine patches are for people who have tobacco use disorder. Slow delivery allows the substance to temporarily stabilize the brain and help reduce withdrawal symptoms over a longer period of time. Research suggests a slower delivery method can reduce the risk of an addiction(4).
Drug Administration(5)
Drug administration is the giving of a drug by one of several means (routes).
| Route | Explanation |
| buccal | held inside the cheek |
| enteral | delivered directly into the stomach or intestine (with a G-tube or J-tube) |
| inhalable | breathed in through a tube or mask |
| infused | injected into a vein with an IV line and slowly dripped in over time |
| intramuscular | injected into muscle with a syringe |
| intrathecal | injected into your spine |
| intravenous | injected into a vein or into an IV line |
| nasal | given into the nose by spray or pump |
| ophthalmic | given into the eye by drops, gel, or ointment |
| oral | swallowed by mouth as a tablet, capsule, lozenge, or liquid |
| otic | given by drops into the ear |
| rectal | inserted into the rectum |
| subcutaneous | injected just under the skin |
| sublingual | held under the tongue |
| topical | applied to the skin |
| transdermal | given through a patch placed on the skin |
| vaginal | inserted into the vagina |
Pharmacokinetics & Pharmacodynamics
Pharmacokinetics is how a body processes a drug whereas Pharmacodynamics takes into account the complex interactions between the drug, the human body, and then the pathogen that might be causing an infection in the patient.
Pharmacokinetics: How Drugs Move through the Body.
Pharmacokinetics: How Drugs Move through the Body. by Professor Dave Explains. We just learned about drug administration, or the ways that drugs can enter the body. What happens next? How do drugs move around the body to get to where they need to go? The study of this is called pharmacokinetics. Let’s get into the basics of this topic now!(6)
Pharmacodynamics: Mechanisms of Drug Action
Pharmacodynamics: Mechanisms of Drug Action. by Professor Dave Explains. Now that we know how drugs move through the body to reach their target, what happens once they get there? By what mechanisms can drugs interact with target proteins to elicit a particular cellular response, and by extension a physiological effect?(7)
CHAPTER CREDIT
Adapted from Unit 4.2 in Exploring Substance Use in Canada by Julie Crouse is licensed under CC BY-NC-SA 4.0 and Unit 2.1 in Drugs, Health & Behavior by Jacqueline Schwab. CC BY-NC-SA. with minor revisions for clarity and ease of use.
References
- Professor Dave Explains. (2020, March 10). Methods of Drug Administration [Video]. YouTube. https://www.youtube.com/watch?v=EakBZqmmfMQ
- Samaha, A-N., & Robinson T. E. (2005). Why does the rapid delivery of drugs to the brain promote addiction? Trends in Pharmacological Sciences, 26(2), 82-87. https://pubmed.ncbi.nlm.nih.gov/15681025/
- Case-Lo, C. (2019, March 28). Medication administration: Why it’s important to take drugs the right way. https://www.healthline.com/health/administration-of-medication
- Genetic Science Learning Center. (2013, August 30). Drug delivery methods. https://learn.genetics.utah.edu/content/addiction/delivery/
- Le, J.(2012, October 12). Introduction to administration and Kinetics of Drugs. Merck Manual Consumer Version. https://www.merckmanuals.com/home/drugs/administration-and-kinetics-of-drugs/introduction-to-administration-and-kinetics-of-drugs
- Professor Dave Explains. (2020b, March 24). Pharmacokinetics: How Drugs Move Through the Body [Video]. YouTube. https://www.youtube.com/watch?v=L1W0q1kEof4
- Professor Dave Explains. (2020c, April 7). Pharmacodynamics: Mechanisms of Drug Action [Video]. YouTube. https://www.youtube.com/watch?v=PGzT3cTPah8
