Component

The ratio of cyclooxygenase-1 to cyclooxygenase-2 inhibitory potency

The ratio of cyclooxygenase-1 to cyclooxygenase-2 inhibitory potency. Species, exposure and limitations are retained in each linked claim.

4 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

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How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

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What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What acts on it

  1. Measurement of the inhibitory potency of non-steroidal anti-inflammatory drugs on cyclooxygenase isoforms is strongly influenced by variations in experimental conditions, the concentration of protein in the assay medium being particularly important because these drugs are highly protein bound in vivo so that assays based on human whole blood provide the most suitable test system, and of the drugs investigated only meloxicam showed selectivity for cyclooxygenase-2 at therapeutically relevant concentrations while standard drugs such as naproxen inhibited both isoforms to an equal degree.

    The human whole blood assay of cyclooxygenase activity → The ratio of cyclooxygenase-1 to cyclooxygenase-2 inhibitory potency source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/ibuprofen-research/9219317.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d3edafe44ec9bf9e15505ffebb96add5467f8874fe8b585ce3878c473f250714", "start_char": 0, "end_char": 1162, "text_sha256": "d3edafe44ec9bf9e15505ffebb96add5467f8874fe8b585ce3878c473f250714"}
    experimental_model
    Comparison of cyclooxygenase inhibitory potency across assay systems, using the human whole blood assay
    exposure
    Standard non-steroidal anti-inflammatory drugs compared at therapeutically relevant concentrations
    limitations
    Argues that the whole blood assay is the appropriate test because these drugs are highly protein bound. It reports conclusions about the class, with naproxen named rather than ibuprofen.
    nutrient_topic
    Ibuprofen research collection; topical membership is not evidence of a direct clinical effect, and the racemate is recorded separately from each of its two enantiomers. · Ibuprofen
    organism
    Human
    plain_language
    Measured in blood rather than in a tube of enzyme, the ordinary anti-inflammatories hit both enzymes about equally.
    primary_references
    [ibu-p9219317] Differentiating among nonsteroidal antiinflammatory drugs by pharmacokinetic and pharmacodynamic profiles. (1997). https://pubmed.ncbi.nlm.nih.gov/9219317/ DOI: 10.1016/s0049-0172(97)80050-9
    tissue_or_cell_type
    Whole blood

    Ibuprofen: the enantiomer that works, the one that was called inactive, the one-way chemistry that turns one into the other, and the targets that are not cyclooxygenase (2026-09-22) · lines 344–355

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Comparison of cyclooxygenase inhibitory potency across assay systems, using the human whole blood assay · source_derived_draft · unverified_draft

    ### ibu-no-selectivity-in-whole-blood Measurement of the inhibitory potency of non-steroidal anti-inflammatory drugs on cyclooxygenase isoforms is strongly influenced by variations in experimental conditions, the concentration of protein in the assay medium being particularly important because these drugs are highly protein bound in vivo so that assays based on human whole blood provide the most suitable test system, and of the drugs investigated only meloxicam showed selectivity for cyclooxygenase-2 at therapeutically relevant concentrations while standard drugs such as naproxen inhibited both isoforms to an equal degree. Condition category: normal nutrient_topic: Ibuprofen research collection; topical membership is not evidence of a direct clinical effect, and the racemate is recorded separately from each of its two enantiomers. plain_language: Measured in blood rather than in a tube of enzyme, the ordinary anti-inflammatories hit both enzymes about equally. organism: Human tissue_or_cell_type: Whole blood experimental_model: Comparison of cyclooxygenase inhibitory potency across assay systems, using the human whole blood assay limitations: Argues that the whole blood assay is the appropriate test because these drugs are highly protein bound. It reports conclusions about the class, with naproxen named rather than ibuprofen. exposure: Standard non-steroidal anti-inflammatory drugs compared at therapeutically relevant concentrations evidence_span: {"source_cache": "artifacts/ibuprofen-research/9219317.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d3edafe44ec9bf9e15505ffebb96add5467f8874fe8b585ce3878c473f250714", "start_char": 0, "end_char": 1162, "text_sha256": "d3edafe44ec9bf9e15505ffebb96add5467f8874fe8b585ce3878c473f250714"} [ibu-p9219317] Differentiating among nonsteroidal antiinflammatory drugs by pharmacokinetic and pharmacodynamic profiles. (1997). https://pubmed.ncbi.nlm.nih.gov/9219317/ DOI: 10.1016/s0049-0172(97)80050-9
    Complete structured claim and evidence

  2. Paracetamol and salicylate are weak inhibitors of both isolated cyclooxygenase-1 and -2 but potent inhibitors of prostaglandin synthesis in intact cells if low concentrations of arachidonic acid are available, the effects of both being overcome by increased hydroperoxide levels; at low arachidonic acid concentrations cyclooxygenase-2 is the major isoenzyme involved when both are present, so these drugs may selectively inhibit synthesis involving cyclooxygenase-2 because the lower flux through that pathway produces less prostaglandin G2 than the pathway involving cyclooxygenase-1, and the authors propose the class name peroxide sensitive analgesic and antipyretic drugs.

    Ambient cellular hydroperoxide concentration → The ratio of cyclooxygenase-1 to cyclooxygenase-2 inhibitory potency source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/paracetamol-research/15035793.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "f72415969de66bea6c0588049cbe1fd1a4b23195c0e2f5a60293eaf99a0f641e", "start_char": 0, "end_char": 1279, "text_sha256": "f72415969de66bea6c0588049cbe1fd1a4b23195c0e2f5a60293eaf99a0f641e"}
    experimental_model
    Review of the mechanism of paracetamol and salicylate as peroxide-sensitive inhibitors
    exposure
    Paracetamol and salicylate at low arachidonic acid concentrations
    limitations
    A review proposing a drug class rather than a new measurement. Its argument that apparent cyclooxygenase-2 selectivity arises from flux rather than binding is the useful part.
    nutrient_topic
    Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. · Paracetamol
    organism
    Human and enzyme
    plain_language
    The apparent preference for the second enzyme may be nothing to do with binding it, and everything to do with how much peroxide each pathway makes.
    primary_references
    [apap-p15035793] Mechanisms of action of paracetamol and related analgesics. (2003). https://pubmed.ncbi.nlm.nih.gov/15035793/ DOI: 10.1163/156856003322699573
    tissue_or_cell_type
    Cyclooxygenase

    Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22) · lines 181–192

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Review of the mechanism of paracetamol and salicylate as peroxide-sensitive inhibitors · source_derived_draft · unverified_draft

    ### apap-apparent-selectivity-from-flux Paracetamol and salicylate are weak inhibitors of both isolated cyclooxygenase-1 and -2 but potent inhibitors of prostaglandin synthesis in intact cells if low concentrations of arachidonic acid are available, the effects of both being overcome by increased hydroperoxide levels; at low arachidonic acid concentrations cyclooxygenase-2 is the major isoenzyme involved when both are present, so these drugs may selectively inhibit synthesis involving cyclooxygenase-2 because the lower flux through that pathway produces less prostaglandin G2 than the pathway involving cyclooxygenase-1, and the authors propose the class name peroxide sensitive analgesic and antipyretic drugs. Condition category: normal nutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. plain_language: The apparent preference for the second enzyme may be nothing to do with binding it, and everything to do with how much peroxide each pathway makes. organism: Human and enzyme tissue_or_cell_type: Cyclooxygenase experimental_model: Review of the mechanism of paracetamol and salicylate as peroxide-sensitive inhibitors limitations: A review proposing a drug class rather than a new measurement. Its argument that apparent cyclooxygenase-2 selectivity arises from flux rather than binding is the useful part. exposure: Paracetamol and salicylate at low arachidonic acid concentrations evidence_span: {"source_cache": "artifacts/paracetamol-research/15035793.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "f72415969de66bea6c0588049cbe1fd1a4b23195c0e2f5a60293eaf99a0f641e", "start_char": 0, "end_char": 1279, "text_sha256": "f72415969de66bea6c0588049cbe1fd1a4b23195c0e2f5a60293eaf99a0f641e"} [apap-p15035793] Mechanisms of action of paracetamol and related analgesics. (2003). https://pubmed.ncbi.nlm.nih.gov/15035793/ DOI: 10.1163/156856003322699573
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Reversible inhibition of both cellular cyclooxygenase-1 and cyclooxygenase-2 was observed with the nonselective drugs ibuprofen and indomethacin, whereas the selective inhibitor DuP-697 was reversible against cyclooxygenase-1 but irreversible against cyclooxygenase-2, and indomethacin displayed time-dependent inhibition of both cellular isoforms; the selectivities and potencies of inhibitors determined using intact cells are affected by substrate concentration and differ from those determined in cell-free microsomal or purified enzyme preparations.

    Ibuprofen → Cyclooxygenase-2 (PTGS2) source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/ibuprofen-research/8831731.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d3161aac692f44c874cafb498e9606f0382b380662ccb58cd1683139f1c1df99", "start_char": 0, "end_char": 1993, "text_sha256": "d3161aac692f44c874cafb498e9606f0382b380662ccb58cd1683139f1c1df99"}
    experimental_model
    Chinese hamster ovary cell lines stably expressing each human cyclooxygenase isoform, with cell-free comparison
    exposure
    Ibuprofen, indomethacin, NS-398 and DuP-697 across intact cells and microsomal preparations
    limitations
    Shows that the selectivity numbers depend on the assay, which bears on every potency ratio quoted for this drug class. A heterologous expression system.
    nutrient_topic
    Ibuprofen research collection; topical membership is not evidence of a direct clinical effect, and the racemate is recorded separately from each of its two enantiomers. · Ibuprofen
    organism
    Human enzyme in hamster cells
    plain_language
    Against both enzymes it is a reversible blocker, and the numbers you get depend on which assay you use.
    primary_references
    [ibu-p8831731] Mechanism of selective inhibition of human prostaglandin G/H synthase-1 and -2 in intact cells. (1996). https://pubmed.ncbi.nlm.nih.gov/8831731/ DOI: 10.1016/0006-2952(96)00462-5
    tissue_or_cell_type
    Intact cells and cell-free preparations

    Ibuprofen: the enantiomer that works, the one that was called inactive, the one-way chemistry that turns one into the other, and the targets that are not cyclooxygenase (2026-09-22) · lines 292–303

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Chinese hamster ovary cell lines stably expressing each human cyclooxygenase isoform, with cell-free comparison · source_derived_draft · unverified_draft

    ### ibu-reversible-against-both-isoforms Reversible inhibition of both cellular cyclooxygenase-1 and cyclooxygenase-2 was observed with the nonselective drugs ibuprofen and indomethacin, whereas the selective inhibitor DuP-697 was reversible against cyclooxygenase-1 but irreversible against cyclooxygenase-2, and indomethacin displayed time-dependent inhibition of both cellular isoforms; the selectivities and potencies of inhibitors determined using intact cells are affected by substrate concentration and differ from those determined in cell-free microsomal or purified enzyme preparations. Condition category: normal nutrient_topic: Ibuprofen research collection; topical membership is not evidence of a direct clinical effect, and the racemate is recorded separately from each of its two enantiomers. plain_language: Against both enzymes it is a reversible blocker, and the numbers you get depend on which assay you use. organism: Human enzyme in hamster cells tissue_or_cell_type: Intact cells and cell-free preparations experimental_model: Chinese hamster ovary cell lines stably expressing each human cyclooxygenase isoform, with cell-free comparison limitations: Shows that the selectivity numbers depend on the assay, which bears on every potency ratio quoted for this drug class. A heterologous expression system. exposure: Ibuprofen, indomethacin, NS-398 and DuP-697 across intact cells and microsomal preparations evidence_span: {"source_cache": "artifacts/ibuprofen-research/8831731.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "d3161aac692f44c874cafb498e9606f0382b380662ccb58cd1683139f1c1df99", "start_char": 0, "end_char": 1993, "text_sha256": "d3161aac692f44c874cafb498e9606f0382b380662ccb58cd1683139f1c1df99"} [ibu-p8831731] Mechanism of selective inhibition of human prostaglandin G/H synthase-1 and -2 in intact cells. (1996). https://pubmed.ncbi.nlm.nih.gov/8831731/ DOI: 10.1016/0006-2952(96)00462-5
    Complete structured claim and evidence

  2. In vitro acetaminophen elicited a 4.4-fold selectivity toward cyclooxygenase-2 inhibition with half-maximal inhibitory concentrations of 113.7 micromolar for cyclooxygenase-1 and 25.8 micromolar for cyclooxygenase-2, following a single oral 1000 milligram dose maximal ex vivo inhibitions were 56% for cyclooxygenase-1 and 83% for cyclooxygenase-2, plasma concentrations remained above the in vitro cyclooxygenase-2 value for at least 5 hours, and ex vivo values compared favourably with in vitro ones; acetaminophen inhibited cyclooxygenase-2 by more than 80%, comparable to non-steroidal anti-inflammatory drugs and selective inhibitors, but the greater than 95% cyclooxygenase-1 blockade relevant for suppression of platelet function was not achieved, and in view of its substantial cyclooxygenase-2 inhibition the cardiovascular warnings defined for selective inhibitors should also be considered.

    Paracetamol → Cyclooxygenase-2 (PTGS2) source_derived_draftungraded
    Experimental context and source evidence
    evidence_span
    {"source_cache": "artifacts/paracetamol-research/17884974.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e2856e9fc1c319219fd3d3cb145f70bb1157f7ca0baa0221594c9583cf7ddc23", "start_char": 0, "end_char": 1857, "text_sha256": "e2856e9fc1c319219fd3d3cb145f70bb1157f7ca0baa0221594c9583cf7ddc23"}
    experimental_model
    Ex vivo and in vitro human whole blood cyclooxygenase assays in five volunteers given a single oral dose
    exposure
    1000 milligrams oral acetaminophen, with coagulation-induced thromboxane B2 and lipopolysaccharide-induced prostaglandin E2 as isoform indices
    limitations
    Measures both isoform indices in dosed people and relates them to plasma concentration. Five volunteers and a single dose.
    nutrient_topic
    Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. · Paracetamol
    organism
    Human
    plain_language
    In people it blocks the second enzyme as hard as a proper anti-inflammatory does, and never blocks the first enough to touch platelets.
    primary_references
    [apap-p17884974] Acetaminophen (paracetamol) is a selective cyclooxygenase-2 inhibitor in man. (2008). https://pubmed.ncbi.nlm.nih.gov/17884974/ DOI: 10.1096/fj.07-8506com
    tissue_or_cell_type
    Whole blood

    Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22) · lines 259–270

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Ex vivo and in vitro human whole blood cyclooxygenase assays in five volunteers given a single oral dose · source_derived_draft · unverified_draft

    ### apap-four-fold-cox2-selective-in-man In vitro acetaminophen elicited a 4.4-fold selectivity toward cyclooxygenase-2 inhibition with half-maximal inhibitory concentrations of 113.7 micromolar for cyclooxygenase-1 and 25.8 micromolar for cyclooxygenase-2, following a single oral 1000 milligram dose maximal ex vivo inhibitions were 56% for cyclooxygenase-1 and 83% for cyclooxygenase-2, plasma concentrations remained above the in vitro cyclooxygenase-2 value for at least 5 hours, and ex vivo values compared favourably with in vitro ones; acetaminophen inhibited cyclooxygenase-2 by more than 80%, comparable to non-steroidal anti-inflammatory drugs and selective inhibitors, but the greater than 95% cyclooxygenase-1 blockade relevant for suppression of platelet function was not achieved, and in view of its substantial cyclooxygenase-2 inhibition the cardiovascular warnings defined for selective inhibitors should also be considered. Condition category: normal nutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. plain_language: In people it blocks the second enzyme as hard as a proper anti-inflammatory does, and never blocks the first enough to touch platelets. organism: Human tissue_or_cell_type: Whole blood experimental_model: Ex vivo and in vitro human whole blood cyclooxygenase assays in five volunteers given a single oral dose limitations: Measures both isoform indices in dosed people and relates them to plasma concentration. Five volunteers and a single dose. exposure: 1000 milligrams oral acetaminophen, with coagulation-induced thromboxane B2 and lipopolysaccharide-induced prostaglandin E2 as isoform indices evidence_span: {"source_cache": "artifacts/paracetamol-research/17884974.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "e2856e9fc1c319219fd3d3cb145f70bb1157f7ca0baa0221594c9583cf7ddc23", "start_char": 0, "end_char": 1857, "text_sha256": "e2856e9fc1c319219fd3d3cb145f70bb1157f7ca0baa0221594c9583cf7ddc23"} [apap-p17884974] Acetaminophen (paracetamol) is a selective cyclooxygenase-2 inhibitor in man. (2008). https://pubmed.ncbi.nlm.nih.gov/17884974/ DOI: 10.1096/fj.07-8506com
    Complete structured claim and evidence

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