Pharmacokinetics studies a drug’s absorption, distribution, metabolism, and excretion (ADME) (Ritter et al., 2008). Pharmacokinetics answers, “How the body handle a drug.” Understanding pharmacokinetics is essential in determining an individual’s choice of drug, dose, route of administration, and dosing interval. This paper is focused on comparing and contrasting the pharmacokinetics of the following class of medication: Non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen. In addition, the paper will list the contraindications and common adverse effects of each class of medication.
Pharmacokinetics
Acetaminophen
Acetaminophen is absorbed in the gastrointestinal tract (GIT) and occurs by passive transport following oral administration. The absorption rate of acetaminophen is rapid in the small intestines, but it occurs slowly in the colon and the stomach. The half-life of acetaminophen is 30-60 minutes, and it undergoes first-pass metabolism. First-pass metabolism is a phenomenon that involves drug metabolization at a specific location in the body before reaching the systemic circulation or site of action. This phenomenon reduces active drug concentration (Gerriets & Nappe, 2019). The rate of gastric emptying influences the absorption of acetaminophen. Acetaminophen is distributed throughout most body tissue and fluids except cerebrospinal fluid and fats. Studies have indicated that the distribution volume of acetaminophen is similar among healthy subjects, the elderly, patients with epilepsy, and gilbert syndrome. The drug does not bind to plasma proteins at therapeutic levels, but 15 -21% is bound at plasma concentration in case of an overdose. The liver is the primary body site for acetaminophen metabolism. Glucuronide and sulfate conjugates are the primary metabolites of acetaminophen. They are converted to N-acetyl-p-benzo-Quinone-imine by CYP-450-dependent hepatic mixed function oxidase. The metabolites undergo conjugation and are rapidly inactivated and excreted as mercapturic acid and cysteine conjugates. Lastly, 2-5% of the therapeutic dose is extracted in the urine unchanged.
NSAIDs
Non-steroidal anti-inflammatory drugs (NSAIDs) treat fever, pain, and inflammation. In other words, they can be used as analgesics, anti-inflammatories, and antipyretic agents. They can be grouped as selective such as celecoxib and valdecoxib, and nonselective such as aspirin, ibuprofen, and meloxicam. NSAIDs work by inhibiting Coenzymes COX 1 and COX 2, which are used in prostaglandin synthesis (Ghlichloo & Gerriets, 2020). They are well absorbed from the GIT following oral absorption. After oral administration, peak blood plasma level occurs after 1-2 hours. NSAIDs have a half-life of between 2-4 hours. The liver is the primary site for NSAID metabolism and is eliminated mainly in the urine and feces.
Contraindications
The contraindication of NSAIDs includes
- A history of NSAIDs or salicylates hypersensitivity
- Severe renal impairment
- Heart failure
- Patients taking anticoagulant
- The third trimester of pregnancy
- A patient who has undergone CABG surgery
- Peptic ulcer
- Bleeding disorder
- In addition, asthmatic patients should avoid NSAIDs due to asthmatic symptoms execration (Ghlichloo & Gerriets, 2020).
The contradiction of acetaminophen includes
- Patients with severe live impairment
- Those taking carbamazepine and isoniazid
- Caution should be taken when administering acetaminophen to patients with liver disease and those who consume alcohol excessively (Gerriets & Nappe, 2019).
Adverse effects
NSAIDs’ adverse effects affect the hepatic, hematological, cardiovascular, gastric mucosa, and cardiovascular system. Therefore, they include acute renal dysfunction, nephrotic syndrome, myocardial infarction, atrial fibrillation, renal papillary necrosis, hepatotoxicity, peptic ulcers, thrombocytopenia, hemophilia, and urticaria (Ghlichloo & Gerriets, 2020).
Acetaminophen-associated adverse effects include nephrotoxicity, anemia, hypersensitivity reaction, neutropenia, decreased serum bicarbonate, hyperuricemia, increased serum glucose, leukopenia, Steven Johnson Syndrome, hepatotoxicity, vomiting, abdominal pain, acute generalized exanthematous pustulosis, and hyperammonemia (Gerriets & Nappe, 2019).
In sum, NSAIDs and acetaminophen are effective analgesic medications but with different pharmacokinetics, contraindications, and adverse effects. For example, the medication class has a different metabolism, including half-life and route of elimination Individuals should stop taking this medication through self-directing and seek a doctor’s guidance.
References
Gerriets, V., & Nappe, T. M. (2019, October 12). Acetaminophen. Nih.gov; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK482369/
Ghlichloo, I., & Gerriets, V. (2020). Non-steroidal Anti-inflammatory Drugs (NSAIDs). PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK547742/
Ritter, M., Lewsi, L., Mant, T., & Ferro, A. (2008). Clinical Pharmacology and Therapeutics. https://www.pharmaresearchlibrary.com/wp-content/uploads/2013/03/A-Textbook-of-Clinical-Pharmacology-and-Therapeutics-5th-edition.pdf
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