(in-hib′ĭt-ŏr)

[L. inhibere, to hold back, restrain]
An agent that blocks a cellular receptor, stops a chemical reaction, prevents an enzyme from working, or suppresses a muscle or nerve.

acetylcholinesterase inhibitor

SEE: Cholinesterase inhibitor.

alpha-2 plasmin inhibitor

SEE: Alpha-2 antiplasmin.

alpha-glucosidase inhibitor

An oral drug that lowers blood sugars by preventing carbohydrate absorption from the gastrointestinal tract.

alpha-reductase inhibitor

A medication to treat benign prostatic hyperplasia. It blocks the conversion of testosterone to dihydrotestosterone.

androgen-signaling targeting inhibitor

Any medication that blocks or alters the binding of male hormones at their receptor sites. Medications from this class are used to treat metastatic prostate cancer.

angiotensin-converting-enzyme inhibitor

ABBR: ACE inhibitor Any of the therapeutic agents that inhibit conversion of angiotensin I to angiotensin II. ACE inhibitors are used to treat hypertension and heart failure and to protect kidney function in patients with diabetes mellitus.

aromatase inhibitor

Any of a class of drugs that block the synthesis of estrogen in the body. A number of these agents have been developed to treat breast cancer, which is often a hormone-responsive malignancy.

attachment inhibitor

SEE: Entry inhibitor.

bcl-2 inhibitor

An agent that blocks the antiapoptotic protein bcl-2 and thereby encourages cell death. These agents are used to treat cancers, esp. chronic lymphocytic leukemias.

bone resorption inhibitor

Any of a class of drugs that prevent or retard osteoporosis. Examples include the bisphosphonates.
Patients with achalasia should avoid these medications because bisphosphonates may cause inflammation and ulceration in the esophagus.

calcitonin-gene related peptide inhibitor

ABBR: CGRP inhibitor Any agent that blocks the vasodilatory and painful effects of calcitonin-gene related peptides. Drugs from this class are used to prevent migraine headaches.

carbonic anhydrase inhibitor

Any agent or medication that blocks the enzymatic hydration of carbon dioxide to carbonic acid. Medications that inhibit carbonic anhydrase are used topically (on to the eye) to lower intraocular pressures. They can also be taken orally, e.g., as diuretics or treatments for mountain sickness.

catechol-O-methyltransferase inhibitor

ABBR: COMT inhibitor An inhibitor such as entacapone or tolcapone used to treat the “wearing off” phenomenon of Parkinson disease. “Wearing off” is the reduction of the rate at which levodopa is metabolized. The COMT inhibitors reduce this rate and prolong the effectiveness of levadopa.

chitin synthase inhibitor

Any agent that prevents chitin, a critical component of fungal cell walls, from forming. Agents from this class may be used to treat serious fungal infections, such as coccidiomycosis.

cholesteryl ester transfer protein inhibitor

Any drug that inhibits the transfer of cholesteryl esters from high-density lipoproteins (HDLs) to other lipoproteins. Drugs from this class increase HDL levels, potentially improving the lipid profiles of patients and decreasing their risk of atherosclerosis.

cholinesterase inhibitor

ABBR: ChEI Any of a class of drugs that prevent the degradation of the neurotransmitter acetylcholine, which is involved in memory and learning. Drugs from this class are used to treat Alzheimer dementia.
SYN: SEE: acetylcholinesterase inhibitor

competitive inhibitor

1. A chemical that binds to or blocks another reagent from participating in a reaction.
2. A medication, hormone, or other intercellular messenger that binds and blocks the cellular receptor or target enzyme of another agent. Drugs that act by competitive inhibition may treat or prevent disease by inactivating pathogenic enzymes or by blocking the effects of hormones or precursor molecules. For example, protease inhibitors interfere with production of HIV by binding and inactivating the protease enzyme; selective estrogen-receptor modulators limit the impact of estrogen by replacing this hormone on cells sensitive to its effects.

cyclooxygenase inhibitor

Any agent that suppresses inflammation by blocking the inflammatory effects of cyclooxygenase.

dipeptidyl peptidase-4 inhibitor

ABBR: DPP-4 inhibitor SEE: Gliptin.

direct thrombin inhibitor

ABBR: DTI Any medication or substance that interferes with the coagulation of blood by blocking the action of thrombin. Unlike heparins, which are anticoagulants that require the presence of antithrombin to inactivate thrombin, DTIs exert their effects without an intermediary. DTIs can be used to treat and prevent clots in both arteries and veins (heparin and warfarin are usually preferred for these uses). They are an alternative to heparin in patients with a history of heparin-induced thrombocytopenia. The primary side effect of DTIs is bleeding.

DPP-4 inhibitor

dipeptidyl peptidase-4 inhibitor.

dual reuptake inhibitor

An antidepressant medication that works by blocking the reuptake of both serotonin and norepinephrine.

entry inhibitor

Any agent that prevents a pathogen, e.g., HIV, from binding to cell membranes and infecting cells.
SYN: SEE: attachment

factor Xa inhibitor

Any drug that prevents blood coagulation by interfering with the activity of coagulation Factor Xa. Examples include: apixaban, edoxaban, and rivaroxaban.

fusion inhibitor

Any drug that prevents a virus from attaching itself to the membrane of a vulnerable cell.

glycoprotein IIB/IIIa receptor inhibitor

Any of a class of drugs that block the fibrinogen receptor on the surface of platelets. Drugs from this class are used to treat acute myocardial infarction, unstable angina pectoris, and other acute coronary syndromes. The most common side effect of treatment with these drugs is bleeding.

helicase-primase inhibitor

Any drug that blocks the replication of herpes simplex virus by targeting enzymes crucial to viral DNA synthesis.

histone deacetylase inhibitor

Any agent that prevents the uncoiling of chromosomes from their condensed form on histones. Drugs from this class limit protein expression, and are used to treat some forms of lymphoma and multiple myeloma.

HMG CoA enzyme inhibitor

SEE: Statin.

If inhibitor

Any drug that blocks the pacemaking current in the heart, slowing the heart rate without reducing the strength of heart muscle contraction.

IL-12/23 inhibitor

Any agent that blocks the pro-inflammatory effect of the cytokines interleukin 12 and interleukin 23. Drugs from this class are used to treat psoriasis and psoriatic arthritis.

IL-17A inhibitor

Any agent that blocks the pro-inflammatory effect of interleukin 17A. Drugs from this class are used to treat psoriasis and psoriatic arthritis.

immune checkpoint inhibitor

Any drug that blocks immune checkpoints and thereby augments the immune response. Checkpoint inhibitors are used in cancer therapy.

integrase strand transfer inhibitor

ABBR: INSTI Any antiretroviral drug that blocks the effect of integrase.
SEE: integrase

interleukin-1 inhibitor

Any drug or monoclonal antibody used to reduce inflammation caused by the release of the cytokine interleukin-1, from leukocytes and other nucleated cells.

JAK inhibitor

Any agent that blocks the effect of Janus kinases on blood cell formation. Drugs from this class are used to treat bone marrow diseases, like polycythemia rubra vera, and rheumatological diseases, like rheumatoid arthritis.

matrix metalloproteinase inhibitor

An agent that inhibits cancer cells by blocking their abilities to invade tissues, demand new blood supply, and metastasize.

metalloprotease inhibitor

SEE: Metalloproteinase inhibitor.

metalloproteinase inhibitor

Any of numerous compounds that inhibit the activity of the metalloproteinase family of enzymes. These agents share the ability to suppress or eliminate the enzyme activity of the metalloproteinases. Agents identified in this group include the tetracycline antibiotics, numerous specially designed synthetic peptides and proteins, chemicals such as ethylenediaminetetra-acetic acid (EDTA), and a variety of agents used in cancer chemotherapy.
SYN: SEE: metalloprotease inhibitor

monoamine oxidase inhibitor

ABBR: MAOI Any of a group of drugs that can be used to treat depression and Parkinson disease. Nonselective versions of these medications produced hypertensive crises and other severe side effects when they were taken with tyramine-containing foods (some cheeses) and several other drugs. Newer members of this class of drugs do not have these effects, but should be used with caution, esp. by those taking selective serotonin reuptake inhibitors.
MAOIs may have unfavorable drug-drug interactions with many anesthetics and should be discontinued approximately 2 weeks before surgery.

SEE: tyramine

neprilysin inhibitor

ABBR: ARNI A medication that blocks (angiotensin and) neprilysin, causing blood vessels to dilate and the kidneys to excrete sodium. It is used to treat heart failure. Adverse effects can include hypotension, reduced kidney function, and increases in serum potassium. VAR: angiotensin-receptor neprilysin inhibitor

neuraminidase inhibitor

Any of a class of antiviral drugs that block neuraminidase, which helps the influenza virus to bud from cells it has infected so that it can spread to other ciliated epithelial cells of the respiratory tract. Agents in this class include oseltamivir and zanamivir.

nonnucleoside analog reverse transcriptase inhibitor

ABBR: NNRTI Any of a class of antiretroviral drugs used to treat those infected with HIV. NNRTIs bind with and inhibit the activity of reverse transcriptase, an enzyme needed to transcribe viral RNA into the host cell DNA. Examples include nevirapine, delavirdine, and efavirenz.

nucleoside reverse transcriptase inhibitor

ABBR: NRTI Any of a class of antiretroviral drugs used to treat patients with HIV infection. NRTIs prevent transcription of viral RNA to host DNA by interfering with the action of the enzyme reverse transcriptase. Zidovudine, dideoxyinosine, zalcitabine, d4T, and abacavir are NRTIs.
SEE: reverse transcriptase inhibitor

PCSK9 inhibitor

Any of a class of drugs that bind to cellular receptors for low-density lipoproteins (LDLs). They are used to improve serum cholesterol levels by improving the clearance of LDLs from the circulation.

phosphodiesterase inhibitor

ABBR: PDE inhibitor Any agent that blocks phosphodiesterase, inhibiting the production of second messengers within cells, such as cyclic adenosine monophosphate or cyclic glucose monophosphate. Drugs that inhibit PDE include sildenafil and other agents used as positive inotropes and vasodilators in heart failure.

phosphodiesterase type-4 inhibitor

ABBR: PDE 4 inhibitor Any agent that blocks the pro-inflammatory effects of phosphodiesterase 4. Drugs from this class are used to treat a wide variety of diseases including rheumatoid arthritis, plaque psoriasis, and COPD with airway inflammation and bronchoconstriction.

PI3K inhibitor

Any agents which block phosphatidylinositol 3-kinase (PI3K) from stimulating cells to take up nutrients, synthesize important molecules, and divide. Agents from this class are used to treat certain cancers.

poly(adenosine diphosphate-ribose) polymerase inhibitor

ABBR: PARP inhibitor A medicine that blocks a DNA repair enzyme (PARP). In some cancers (e.g., ovarian cancer), PARP helps repair malignant cells with DNA lesions. Inhibitors of PARP prevent the cells from fixing themselves.

polymerase acidic endonuclease inhibitor

A medication that interferes with influenza viral RNA transcription, reducing both the duration of symptomatic influenza and the time when infected patients shed live virus.

proprotein convertase subtilisin-kexin type 9 inhibitor

A monoclonal antibody used to treat elevated low density lipoprotein cholesterol levels.

prostaglandin inhibitor

A substance that inhibits the production of prostaglandins. Nonsteroidal and steroidal anti-inflammatory agents are two major categories of such inhibitors.

protease inhibitor

1. A substance that inhibits the action of enzymes.
2. Any of a class of medications that prevent immature virions (as of hepatitis viruses or HIV) from assembling into structures capable of replication.

proteasome inhibitor

Medications that prevent cells from degrading and destroying potentially toxic proteins. Examples, including bortezomib, carfilzomid, and ixazomib, are used to treat multiple myeloma.

proton pump inhibitor

ABBR: PPI Any of a class of medications that eliminate acid production in the stomach. These drugs are used to treat peptic ulcers, gastroesophageal reflux disease, infection with Heliobacter pylori, and related disorders. Omeprazole and lansoprazole are members of this drug class.

reverse transcriptase inhibitor

ABBR: RTI Any of a class of antiretroviral agents that competitively inhibit the reverse transcriptase enzyme of HIV and other viruses.
SEE: antiretroviral

Rho kinase inhibitor

A medication that increases resistance in the trabecular network; used to lower intraocular pressure.

selective serotonin reuptake inhibitor

ABBR: SSRI Any of a class of drugs that interfere with serotonin transport and are used to treat depression, obsessive-compulsive behaviors, eating disorders, and social phobias. Examples include fluoxetine (Prozac), paroxetine (Paxil), and sertraline.
The use of SSRIs in the treatment of depression may sometimes be associated with an increased risk of suicide, esp. during the initiation of treatment. The risk is greatest among children and adolescents. All patients who begin treatment with SSRIs should be monitored closely for evidence that they intend to harm themselves.

serine protease inhibitor

ABBR: serpin Any of the compounds that inhibit platelet function and coagulation. Serpins have been used to reduce deposition of microemboli in cases of disseminated intravascular coagulation associated with sepsis.

serotonin and norepinephrine reuptake inhibitor

ABBR: SNRI An antidepressant medication (such as duloxetine or venlafaxine) that elevates mood by blocking neurons from taking up both norepinephrine and serotonin. Combined reuptake inhibitors differ from medications such as sertraline (Zoloft) or fluoxetine (Prozac), which are relatively selective serotonin reuptake inhibitors, and from tricyclic antidepressants, which primarily prevent the reuptake of norepinephrine by brain cells. SNRIs treat neuropathic pain as well as depression.

sodium-glucose cotransporter 2 inhibitor

ABBR: SGLT-2 inhibitor Any drug, such as dapaglifozin or canagliflozin, that reduces serum blood sugars by increasing the urinary excretion of glucose.

T-cell activation inhibitor

Any agent that blocks T-cells from mounting a cellular immune response. Drugs from this class are immunomodulators and are used to treat conditions like rheumatoid arthritis.

tubulin inhibitor

Any drug that blocks the polymerization of microtubules in cells, and thereby preventing mitosis from occurring. An example of a drug from this class is colchicine.

tumor necrosis factor alpha inhibitor

ABBR: TNF inhibitor A drug that blocks the effects of tumor necrosis factor alpha (TNF-α), a biologically active cytokine that is a critical element of the inflammatory response. Such drugs, which include adalimumab, etanercept, and infliximab, are agents used to treat autoimmune illnesses such as rheumatoid arthritis.
Because these drugs are immunologically active, patients with active infection or those with chronic infections such as tuberculosis should not use them. These agents also sometimes increase the risk of cancers and have rarely been associated with demyelinating diseases of the central nervous system such as multiple sclerosis.

vascular endothelial growth factor inhibitor

Any agent or medication that blocks the growth of blood vessels and decreases blood vessel permeability. Drugs from this class are used (by intraocular injection) to treat “wet” age-related macular degeneration.

vasopeptidase inhibitor

Any of a class of medications that blocks the actions of both angiotensin-converting enzymes (ACE) and neural endopeptidase. Drugs from this class may be used to treat heart failure.

visceral adipose tissue-derived serine protease inhibitor

SEE: Vaspin.

xanthine oxidase inhibitor

Any drug, such as allopurinol or febuxostat, that decreases serum uric acid concentrations by inhibiting the enzyme xanthine oxidase.