Ibuprofen pharmacokinetics
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Ibuprofen Pharmacokinetics: Absorption, Distribution, Metabolism, and Excretion
Absorption and Formulation Differences
Ibuprofen is absorbed rapidly after oral administration, but the rate and extent of absorption can vary depending on the formulation. Fast-acting formulations like ibuprofen arginine and solubilized capsules reach peak plasma concentrations much faster (median times to maximum concentration: 0.42 and 0.5 hours) compared to standard ibuprofen tablets (1.25 hours). These fast-acting forms also achieve higher peak concentrations, although the overall exposure (AUC) is similar across formulations. Rapid absorption leads to more pronounced COX2 inhibition, which may enhance therapeutic effects in the early hours after dosing . Feeding can delay absorption, increasing both the absorption half-life and lag time, especially for tablet formulations .
Distribution and Protein Binding
Ibuprofen is highly bound to plasma proteins, with the free fraction remaining low (about 5.5%) at therapeutic concentrations. However, at higher concentrations, protein binding becomes more concentration-dependent, and the free fraction can increase significantly . The drug is best described by a two-compartment open model, and its distribution is influenced by body composition, with fat mass being an important covariate for both clearance and volume of distribution 29.
Metabolism and Nonlinear Kinetics
Ibuprofen undergoes extensive hepatic metabolism, primarily to OH-ibuprofen and COOH-ibuprofen. The pharmacokinetics of total ibuprofen show a nonlinear relationship with dose, meaning that as the dose increases, the area under the curve (AUC) for total ibuprofen does not increase proportionally. However, the AUC for free (unbound) ibuprofen is linearly related to dose, indicating that oral clearance based on free drug is dose-independent . In rats, systemic plasma clearance decreases with increasing dose, mainly due to reduced metabolic clearance to OH-ibuprofen, and the mean residence time increases .
Excretion
Ibuprofen and its metabolites are primarily excreted in the urine. The efficiency of absorption and urinary recovery of ibuprofen is generally dose-independent in humans, but in animal studies, higher doses result in a lower percentage of the drug being excreted in the urine, mainly due to changes in metabolite recovery 13.
Special Populations: Age, Disease, and Ethnicity
- Children and Premature Infants: In premature infants, ibuprofen pharmacokinetics show wide variability, with a much longer elimination half-life (average 15.7 hours) compared to adults. Factors like gestational age, birth weight, and sex do not significantly affect pharmacokinetics in this group . In children with cystic fibrosis, ibuprofen clearance is increased and exposure is reduced compared to healthy children, but the drug remains well-tolerated .
- Elderly and Disease States: Advanced age, alcoholic liver disease, and rheumatoid arthritis have minimal influence on ibuprofen pharmacokinetics .
- Ethnic Differences: Studies show that intravenous ibuprofen has similar pharmacokinetic profiles in Chinese and Caucasian populations, both in adults and children, supporting the use of the same dosing regimens across these groups 510.
Enantioselective Pharmacokinetics
Ibuprofen is a chiral drug, and its pharmacokinetics are enantioselective. The S-enantiomer (dexibuprofen) is the active form, and there is metabolic chiral inversion from the R- to the S-enantiomer. Protein binding, metabolism, and chiral inversion mechanisms are important for understanding the drug’s pharmacological and toxicological effects, as well as potential drug interactions .
Drug Interactions
Ibuprofen can be combined with acetaminophen without altering its pharmacokinetic profile. However, co-administration with aspirin may reduce ibuprofen plasma levels to less than half, potentially impacting its efficacy .
Conclusion
Ibuprofen pharmacokinetics are influenced by formulation, dose, body composition, and special populations such as infants and those with cystic fibrosis. The drug is rapidly absorbed, highly protein-bound, and primarily metabolized in the liver. While most factors like age, disease, and ethnicity have minimal impact, formulation and feeding can significantly affect absorption rates. Understanding these pharmacokinetic properties is essential for optimizing ibuprofen therapy across diverse patient groups 1234+6 MORE.
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Most relevant research papers on this topic
Enantioselective Pharmacokinetics of Ibuprofen and Involved Mechanisms
Ibuprofen's chiral pharmacokinetics and mechanisms may provide insights into other chiral drugs, aiding in understanding and predicting clinical drug interactions and pathological states.
Pharmacokinetics of Oral Ibuprofen in Premature Infants
Oral ibuprofen pharmacokinetics show wide variability in premature infants, warranting revision of the dosage schedule to achieve comparable plasma concentrations for successful patent ductus arteriosus closure.
Comparison of intravenous ibuprofen pharmacokinetics between Caucasian and Chinese populations using physiologically based pharmacokinetics modeling and simulation.
Intravenous ibuprofen pharmacokinetics are analogous in Caucasian and Chinese populations, with no significant differences observed in adult or pediatric populations.
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