Top 100 Mechanism of Action

Drug / Drug ClassMechanism of Action
AcetylcysteineReplenishing glutathione to conjugate toxic NAPQI in acetaminophen overdose.
Activated charcoalIncreased elimination of poisons by adsorbing chemical molecules onto the surface of charcoal – reducing systemic absorption of the toxin. Activated charcoal is used as an antidote for any oral toxins.
AdenosineAgonist at adenosine receptors – activating GPRCs to reduce the frequency of spontaneous depolarizations and increasing refractoriness to depolarisation.In turn, this leads to reduction of sinus rate, conduction velocity and increases AV node refractoriness – breaking re-entry circuits. Adenosine is used to treat supraventricular tachycardia (SVT).
EpinephrineAgonist at alpha-1, alpha-2, beta-1 and beta-2 receptors – corresponding to a wide array of flight-or-fight effects.
Aldosterone antagonistsExamples include spironolactone and eplerenone. Aldosterone antagonists competitively bind to the aldosterone receptor – increasing sodium / water excretion and potassium retention.
Alginates / antacidsAntacids work by buffering stomach acids. Alginates work by increasing the viscosity of gastric contents, reducing gastric acid reflux into the esophagus.
AllopurinolXanthine oxidase inhibitor. Febuxostat, another anti-gout drug, also works via this means. Allopurinol is used to prevent acute attacks of gout, not to treat an active attack.
Alpha blockersExamples include doxazosin, tamsulosin and terazosin. Alpha blockers are selective for the alpha-1 adrenoceptor of smooth muscle. For this reason, alpha blockers are used to relieve symptoms of patients with BPH.
AminoglycosidesProtein synthesis inhibitors – irreversibly binding to the 30S subunit. This is an oxygen-dependent mechanism, meaning aminoglycosides are ineffective against anaerobes. They are only effective against Gram-negative aerobes. Examples include gentamicin and tobramycin.
AminosalicylatesAminosalicylates include mesalamine – a drug used to treat ulcerative colitis. The active ingredient is 5-aminosalicylic acid (5-ASA); an intermediate with anti-inflammatory and immunosuppressive properties.
AmiodaroneAmiodarone is used to treat a variety of tachyarrhythmias. Amiodarone works via blockade of sodium, calcium and potassium channels and antagonism at both alpha and beta receptors. It is a class III antiarrhythmic drug.
ACE inhibitorsInhibitors of the enzyme angiotensin-converting enzyme; the enzyme that converts angiotensin I into angiotensin II. Angiotensin II is responsible for aldosterone release, vasoconstriction and fluid retention. Examples include ramipril, perindopril and lisinopril.
Angiotensin receptor blockersARBs work in a similar manner to ACE inhibitors – blocking the action of angiotensin II on the AT1 receptor. ARBs are often used when the persistent,dry cough (caused by kinin accumulation) associated with ACE inhibitors becomes intolerable. Examples include losartan and candesartan.
Antidepressants – SSRIsSelective serotonin reuptake inhibitors; as the name suggests, they increase serotonin availability in the synapse by inhibiting its reuptake by neurons – meaning greater availability to bind to and react with postsynaptic neurons.Examples include citalopram, sertraline, paroxetine and fluoxetine.
Antidepressants – Tricyclic antidepressantsDrugs that inhibit neuronal reuptake of serotonin and norepinephrine. Examples include amitriptyline, nortriptyline and imipramine. Venlafaxine is anon-tricyclic drug that acts as an SNRI.

Antiemetics –

D2 antagonists

Many D2 receptor antagonists are used to prevent and treat nausea and vomiting – particularly in the context of reduced gut motility. D2 receptors are highly concentrated in the chemoreceptor trigger zone (CTZ). Examples include metoclopramide and domperidone (not available in US).

Antiemetics –

H1 antagonists

Examples include cyclizine and promethazine. Used to treat nausea and vomiting – particularly in motion sickness and vertigo. H1 receptors are highly concentrated in the communication of the CTZ with the vestibular system.

Antiemetics –

Phenothiazines

Examples include prochlorperazine and chlorpromazine. Used to treat nausea / vomiting but, due to adverse effects, other drugs are preferred. They may also be used to treat schizophrenia. They act as D2 antagonists in the CTZ and also play a role with H1 receptors between the CTZ and vestibular system – meaning they can be used in a broad range of contexts.

Antiemetics –

5-HT3 antagonists

Drugs that are also known as ‘setrons’. Examples include ondansetron and granisetron. Particularly effective in the context of general anesthesia and chemotherapy-induced nausea and vomiting. 5-HT3 receptors are serotonergic receptors of which a high density can be found in the CTZ and gut (via vagus nerve).

Antifungal drugs –

Azoles

Examples include clotrimazole, fluconazole, ketoconazole and a range of other ‘azole’ drugs. Azoles work by inhibiting ergosterol synthesis, interrupting the integrity of the cell membrane.

Antihistamines –

H1 antagonists

Examples include cetirizine, loratadine, fexofenadine and chlorphenamine. H1receptors, once activated from histamine released from mast cells, are responsible for a range of allergy-type symptoms. Second-generation drugs cross the blood-brain barrier to a significantly lesser extent and so are not associated with sedation.

Antimotility Drugs –

Loperamide

Mu-opioid receptor agonist – leading to reduced bowel motility and hardening of stools. As an opioid, it may lead to constipation, particularly at higher doses.

Antimuscarinics –

Bronchodilators

Examples include ipratropium and tiotropium. Competitive inhibitors of the acetylcholine receptor. Used in the treatment of asthma and COPD, often in conjunction with a steroid.

Antimuscarinics –

Urinary system

Examples include oxybutynin, solifenacin and tolterodine – drugs used to reduce urinary frequency, urgency and urge incontinence in patients with overactive bladder. They are selective for the M3 receptor to exert their clinical effects.

Antipsychotics –

Typical

Examples include haloperidol and prochlorperazine. Typical, or first-generation agents, are associated with a greater degree of extrapyramidal effects compared to second-gen drugs. Typical antipsychotics work by blocking postsynaptic D2 receptors in the mesolimbic-mesocortical pathway.

Antipsychotics –

Atypical

Examples include quetiapine, olanzapine, risperidone and clozapine. Associated with metabolic side effects such as weight gain and diabetes. They also work by blocking D2 receptors.
AspirinIrreversible inhibition of the cyclooxygenase enzyme.
BenzodiazepinesEnhance binding of GABA to the GABA A receptor. Examples include diazepam, nitrazepam and midazolam.
Beta-2 agonistsExamples include albuterol, salmeterol, formoterol and terbutaline. Act as agonists at the beta-2 receptor that leads to smooth muscle relaxation. Beta-2 agonists also cause a shift of potassium to the intracellular compartment, making them a useful means to immediately reduce high potassium levels.
Beta-blockersExamples include metoprolol, bisoprolol, sotalol and propranolol. Beta-1 receptors impact cardiac function, whereas beta-2 receptors impact pulmonary function. Beta-blockers reduce myocardial contractile force and conduction speed. In atrial fibrillation, beta blockers prolong the refractory period at the AV node.
BisphosphonatesExamples include alendronic acid, pamidronate and zoledronic acid. Used to treat osteoporosis, severe hypercalcemia in cases of malignancy and Paget’s disease of bone. Bisphosphonates work by inhibiting the effect of osteoclasts,reducing bone turnover. Bisphosphonates structurally resemble pyrophosphate.
Calcium channel blockersExamples include the non-dihydropyridine verapamil and diltiazem; and the dihydropyridines such as nifedipine and amlodipine. Blockade of calcium entry leads to vasodilation in arterial smooth muscle, reduce myocardial contractility, suppress cardiac conduction and reduce myocardial oxygen demand.
CarbamazepineInhibition of neuronal sodium channels. Carbamazepine is used to treat seizures, trigeminal neuralgia and bipolar disorder.
CephalosporinsAntimicrobial activity is down to the presence of the beta-lactam ring – inhibiting cross-linkage of peptidoglycan and compromising the structure of the microbial cell wall. Examples include ceftriaxone, cefazolin and cefoxitin.
ClopidogrelIrreversible inhibition of the P2Y12 receptor found on platelets – preventing platelet aggregation. Prasugrel also acts by this means. Ticagrelor acts via the same means, except that it acts reversibly.

Corticosteroids –

Systemic

Examples include prednisolone, dexamethasone and hydrocortisone. Systemic corticosteroids work by modifying the immune response – upregulating anti-inflammatory genes and downregulating anti-inflammatory genes. Systemic corticosteroids suppress circulating monocytes and eosinophils.

Corticosteriods –

Inhaled

Examples include beclometasone, budesonide and fluticasone. Inhaled corticosteroids work by reducing mucosal inflammation, widening airways, reducing mucus secretion and reducing exacerbations in patients with asthma or COPD.

Corticosteroids –

Topical

Examples include hydrocortisone and betamethasone. Mechanism is much the same as that described above. Topical corticosteroids applied at high doses may have a systemic effect. Avoid where active infection is present on the skin.
DigoxinDigoxin works as a negative chronotrope (reducing heart rate) and a positive inotrope (increase myocardial contractile force). It reduces conduction at the AV node through increased vagal tone. Digoxin is used in atrial fibrillation /flutter and, in some cases, in the management of heart failure.
Dipyridamole

Works as an adenosine reuptake inhibitor and as an inhibitor of

phosphodiesterase-type 5.

Diuretics –

Loop

Act at ascending loop of Henle – inhibiting the Na+/K+/Cl- co-transporter – the pump responsible for sodium, potassium and chloride transport. Water follows by osmosis. Loop diuretics also act via dilatation of capacitance veins.Examples include furosemide and bumetanide.

Diuretics –

Potassium-sparing

Amiloride

Examples include amiloride. Amiloride work by enhancing diuresis of other diuretics, such as thiazide diuretics, and by retaining potassium. In this way,amiloride improves diuresis, avoids hypokalemia and reduces adverse effects associated with the second diuretic. Amiloride acts on the distal convoluted tubule.

Diuretics –

Thiazide

Thiazide diuretics act by inhibiting the sodium-chloride co- transporter found in the distal convoluted tubule. Examples include bendroflumethiazide,hydrochlorothiazide, indapamide and chlorthalidone. 

Dopaminergic drugs –

Levodopa

Ropinirole

Pramipexole

Levodopa is used alongside a peripheral dopa-decarboxylase inhibitor, such as carbidopa, to prevent peripheral conversion of levodopa into dopamine.Parkinson’s disease results in part from dopamine deficiency in the nigrostriatal pathway. Levodopa works to regenerate dopamine levels. Other dopaminergic drugs, such as ropinirole and pramipexole, work as agonists atD2 receptors. Pramipexole has also been used to treat restless legs syndrome.

Fibrinolytic drugs –

Alteplase

Reteplase

Thrombolytic drugs work by dissolving fibrinous clots and re-canalising occluded blood vessels. These drugs are also known as tissue plasminogen activators (tPAs).
Pregabalin / GabapentinThough structurally GABA analogs, they do not work via this means. Instead, they act at voltage-gated calcium channels (alpha-2 delta) to prevent calcium release and subsequent neurotransmitter release. Both drugs are used to treat seizures and neuropathic pain. Gabapentin may also be used for migraine prophylaxis. Pregabalin has been used to treat GAD.
H2 antagonistsExamples include ranitidine. H2 antagonists work by reducing gastric acid secretion by inhibiting histamine release from enterochromaffin-like cells (ECL) and preventing its binding to H2 receptors on gastric parietal cells. H2 antagonists are used to treat peptic ulcer disease and GERD.
HeparinsHeparins work by inhibiting thrombin and factor Xa in the final blood coagulation pathway. LMWHs – such as enoxaparin and dalteparin – preferentially inhibit factor Xa. Fondaparinux inhibits factor Xa only.
InsulinExamples include aspart, glargine and insulin detemir. Insulin works in much the same way as endogenous insulin – promoting glucose reuptake into cells and tissues, reducing circulating glucose levels. Insulin stimulates glycogen,lipid and protein synthesis and reduces gluconeogenesis.
IronReplenish iron stores to treat and prevent iron-deficiency anemia. Iron, as a divalent ion, interferes with the mechanism and absorption of levothyroxine,fluoroquinolones, tetracyclines and bisphosphonates.

Laxatives –

Bulk-forming

Examples include ispaghula husk, methylcellulose and sterculia. They attract water into the stool, increasing bulk, which stimulates peristalsis.

Laxatives –

Osmotic

Examples include lactulose, macrogol and phosphate enema. Osmotic laxatives work by osmotically drawing water into stools and stimulating peristalsis. Lactulose also works to reduce ammonia absorption and so may be used to treat hepatic encephalopathy.

Laxatives –

Stimulant

Examples include senna, bisacodyl, glycerol suppositories and docusate sodium. Stimulant laxatives work by increasing water and electrolyte secretion into stools, stimulating peristalsis.
LidocaineLidocaine blocks voltage-gated sodium channels, hence its use as a local anesthetic and, more rarely, in treating arrhythmias. Sodium blockade prevents initiation and propagation of action potentials.
MacrolidesExamples include clarithromycin and erythromycin. Macrolides are protein synthesis inhibitors – binding to the 50S subunit and blocking translocation.
MetforminA biguanide anti-diabetic drug that works by increasing insulin sensitivity.Metformin works by suppressing hepatic glucose production, increasing glucose uptake into cells and tissues, and inhibiting intestinal glucose absorption. Unlike other oral anti-diabetic drugs, metformin is not associated with weight gain.
MethotrexateMethotrexate works via two means. It is both an anticancer drug and a DMARD. It inhibits dihydrofolate reductase – preventing cellular replication, hence its use in cancer. As a DMARD, methotrexate also modifies the immune response to downregulate pro-inflammatory mediators and cytokines.
MetronidazoleAn antibacterial and anti-protozoal drug that works by damaging cellular DNA.Metronidazole is only effective against anaerobic bacteria, causing substantial damage to microbial DNA and causing cell death.
NaloxoneAn antidote to opioid toxicity. Naloxone is a competitive opioid receptor antagonist.

Nitrates –

Isosorbide mononitrate

Nitroglycerin

Nitrates work by converting to nitric oxide (NO) in vivo, leading to a reduction of intracellular calcium. In turn, this leads to relaxation of venous capacitance vessels – reducing cardiac preload and myocardial oxygen demand.
NitrofurantoinAn antibacterial drug used to treat UTIs. Nitrofurantoin works by creating free radicals that damages bacterial DNA.
NSAIDsNon-steroidal anti-inflammatory drugs that work by inhibiting cyclooxygenase enzymes. Therapeutic effects drive from COX-2 inhibition. Most undesirable side effects drive from COX-1 inhibition. Examples include ibuprofen, aspirin and ketorolac.
Progestogens / EstrogensExamples include ethinylestradiol products and desogestrel. These drugs work in part by suppressing LH/FSH release and, as a result, ovulation.
OpioidsMu-opioid receptor agonists used to treat pain. Examples include codeine, tramadol, morphine and oxycodone.
OxygenOxygen works by increasing oxygen deliver to hypoxic tissues. Oxygen is used to accelerate reabsorption of pleural gas in pneumothorax and to reduce half-life of carboxyhemoglobin in cases of carbon monoxide poisoning.
AcetaminophenAcetaminophen is a weak COX inhibitor. Its precise mechanism is not yet fully elucidated. It is used to treat pain and fever. Due to the fact it has weak anti-inflammatory activity, acetaminophen is not classified as an NSAID.
PenicillinsBeta-lactam drugs that work as antimicrobials – disrupting peptidoglycan cross-linkage, leading to a compromised cell wall and subsequent lysis and cell death. Examples include benzylpenicillin, flucloxacillin, piperacillin and amoxicillin.
PhenytoinPhenytoin works by binding to sodium channels in their inactive state, prolonging inactivity. Phenytoin reduces electrical conductance and neuronal activity in the brain. It is used to treat status epilepticus among other seizure states.
PDE5 inhibitorsExamples include sildenafil and tadalafil. Both drugs work as phosphodiesterase-type 5 inhibitors – enhancing the effects of nitric oxide to cause vasodilation and increase penile blood flow. Both drugs are used to treat erectile dysfunction and pulmonary arterial hypertension.

Prostaglandin analogs –

Latanoprost

Bimatoprost

Analogs of prostaglandin F2 alpha – reducing intraocular pressure and increasing aqueous humor flow through the uveoscleral pathway. Both drugs are used for ocular hypertension and open-angle glaucoma.
Proton-pump inhibitorsExamples include lansoprazole, omeprazole and pantoprazole. Inhibit the terminal phase of gastric acid production through irreversible inhibition of the hydrogen-potassium pump found on gastric parietal cells.
QuinineOriginally derived from the bark of the Cinchona tree. Quinine is used to treat malaria – killing the parasite in the schizont stage and preventing it from metabolizing hemoglobin. Quinine also reduces neuronal excitability at the motor-end plate and so has been used to treat leg cramps.
FluoroquinolonesExamples include ciprofloxacin and levofloxacin – drugs that act by inhibiting DNA synthesis. Later drugs – such as moxifloxacin and levofloxacin – have greater activity against Gram-positive organisms.
StatinsHMG-CoA reductase inhibitors – the enzyme responsible for making cholesterol. Examples include simvastatin, lovastatin and pravastatin.
SulfonylureasExamples include glyburide and gliclazide. Sulfonylureas work by stimulating pancreatic insulin release. In other words, they work as secretagogues that block the potassium channel on pancreatic beta-cells. This causes depolarisation of the cell membrane and opens calcium channels. Higher intracellular calcium leads to higher insulin release.
TetracyclinesTetracyclines are protein synthesis inhibitors – binding to the 30S ribosomal subunit and preventing binding of tRNA to mRNA – preventing chain elongation. Examples include minocycline and doxycycline.
ThiazolidinedionesAlso known as glitazones, these drugs work as PPAR-gamma agonists – inducing genes to enhance the effects of insulin on muscle, adipose tissue and the liver – increasing glucose uptake and reducing gluconeogenesis. Examples include pioglitazone.

Thyroid Hormones –

Levothyroxine

Liothyronine

Levothyroxine is synthetic T4 and is used to replenish deficient thyroid hormone levels. Liothyronine is synthetic T3. Both drugs are used to treat hypothyroidism.
TrimethoprimTrimethoprim inhibits bacterial folate synthesis, thereby interfering with DNA synthesis. Trimethoprim is effective in the treatment of UTIs and to treat / prevent pneumocystis pneumonia in immunocompromised patients.
ValproateValproate works in part by inhibiting neuronal sodium channels. It also increases GABA levels in the brain. For these reasons, valproate is used to treat epilepsy and bipolar disorder.
VancomycinAn antibacterial drug that works to treat Gram-positive infections. Specifically, vancomycin works by inhibiting cell wall synthesis.
WarfarinWarfarin works by inhibiting vitamin K epoxide reductase – preventing vitamin K reactivation and the synthesis of pro-coagulation factors. Phytomenadione is an antidote to warfarin toxicity.

Z-drugs –

Zopiclone

Zolpidem

Zaleplon

Z-drugs are used for the short-term treatment of insomnia, up to 4 weeks. They are not benzodiazepines, but they are structurally related. Z-drugs work by enhancing the binding of GABA to the GABA A receptor.
CarbapenemsExamples include imipenem and meropenem. Carbapenems work as cell wall synthesis inhibitors. Imipenem is always given alongside cilastatin to prevent its degradation by the renal enzyme dehydropeptidase 1.
OxazolidinonesExamples include linezolid. Linezolid acts as a protein synthesis inhibitor at the initiation step. Linezolid is also a weak MAO inhibitor and so increases risk of serotonin syndrome.
Alkylating agentsAlkylating agents include cyclophosphamide, carmustine, lomustine and busulfan. Alkylating-like drugs include the platinum compounds cisplatin and carboplatin. Alkylating agents work by attaching an alkyl group (CnH2n +1) to the guanine base of DNA, at the #7 nitrogen atom of the purine ring.
MAO inhibitorsMAO inhibitors inhibit the monoamine oxidase enzyme and are used to treat depression. There are two isoforms: MAO-A and MAO-B. Selegiline and rasagiline are selective MAO-B inhibitors. Selective MAO-A inhibitors include moclobemide; whilst non-selective drugs include isocarboxazid, phenelzine and tranylcypromine.
5-alpha reductase inhibitorsInclude finasteride and dutasteride. Both drugs are used to treat BPH and androgenic alopecia. Dutasteride inhibits all three isoforms of the 5-alpha reductase enzyme, whereas finasteride inhibits only isoforms II and III. Both drugs reduce DHT levels.
EtanerceptEtanercept is a DMARD that works as a decoy receptor for TNF. It is used for a wide variety of autoimmune disorders.
LeflunomideLeflunomide is a pyrimidine synthesis inhibitor – specifically by inhibiting dihydroorotate dehydrogenase. Leflunomide is also a DMARD used to treat conditions such as rheumatoid arthritis and psoriatic arthritis.
TaxanesTaxanes are chemotherapeutic drugs that include paclitaxel and docetaxel. Both drugs inhibit microtubule formation, microtubules being fundamental to the process of cell division.
Vinca alkaloidsVinca alkaloids are also chemotherapeutic drugs. Examples include vincristine and vinblastine. Vinca alkaloids work by actin on tubulin, preventing it from developing into microtubules necessary to complete the process of cell division.
FibratesFibrates include drugs such as fenofibrate. They are PPAR-alpha agonists – an effect that impacts the modulation of fat and carbohydrate metabolism. Fibrates also work by modulating adipose tissue differentiation. They are consequently used in the treatment of hypercholesterolemia.
PyridostigmineA drug used to treat myasthenia gravis. Pyridostigmine works as a neuromuscular blocking drug of the non-depolarizing type. The drug inhibits acetylcholinesterase in the synaptic cleft, reducing hydrolysis of acetylcholine.
SevelamerSevelamer is used to reduce phosphate levels in the blood. It may, for example, be used in chronic kidney disease where phosphate levels often elevate. Amine groups on sevelamer become protonated in the intestine and capture phosphate ions.
LithiumLithium is used to treat bipolar disorder and major depressive disorder. Its mechanism of action is not yet fully elucidated, but it is believed to act in part by decreasing norepinephrine release and increasing serotonin release.
FilgrastimFilgrastim is used to promote neutrophil production – for example, in patients with neutropenia from chemotherapy. Filgrastim works as a recombinant form of naturally-occurring granulocyte colony stimulating factor (G-CSF) –increasing neutrophil production.

Antiarrhythmic drugs

Class I

Class II

Class III

Class IV

Antiarrhythmic drugs work as specified by the Vaughan-Williams classification. Class I drugs work as sodium channel blockers (quinidine and procainamide). Class II drugs work as beta-blockers (metoprolol, nebivolol). Class III drugs work via potassium-channel block (amiodarone, sotalol dronedarone). Class IV drugs work as calcium channel blockers (diltiazem, verapamil). Adenosine is sometimes classified as a class V drug.
HIV Drugs

Entry inhibitors

Maraviroc, enfuvirtide

Nucleoside reverse transcriptase inhibitors (NRTIs)

Zidovudine, didanosine, stavudine, lamivudine, abacavir, emtricitabine, entecavir

Non-nucleoside reverse transcriptase inhibitors (NNRTIs)

Efavirenz, nevirapine, rilpivirine

Nucleotide RTIs

Tenofovir, adefovir

Integrase inhibitors

Dolutegravir, elvitegravir, raltegravir

Protease inhibitors

Lopinavir, ritonavir, amprenavir, saquinavir, nelfinavir

CYP 3A inhibitors

Cobicistat

Sofosbuvir / Ledipasvir

Combination medicine (Harvoni) used to treat hepatitis C.

Sofosbuvir works by inhibiting the protein NS5B.

Ledipasvir works by inhibiting the viral protein NS5A.

The combined effect is to inhibit viral replication.