Drug / Drug
Class

Mechanism
of Action

Acetylcysteine

Replenishing
glutathione to conjugate toxic NAPQI in acetaminophen overdose.

Activated
charcoal

Increased
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.

Adenosine

Agonist
at adenosine receptors – activating GPRCs to reduce the frequency of
spontaneous depolarisations 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).

Epinephrine

Agonist
at alpha-1, alpha-2, beta-1 and beta-2 receptors – corresponding to a wide
array of flight-or-fight effects.

Aldosterone
antagonists

Examples
include spironolactone and eplerenone. Aldosterone antagonists competitively
bind to the aldosterone receptor – increasing sodium / water excretion and
potassium retention.

Alginates /
antacids

Antacids
work by buffering stomach acids. Alginates work by increasing the viscosity
of gastric contents, reducing gastric acid reflux into the esophagus.

Allopurinol

Xanthine
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
blockers

Examples
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.

Aminoglycosides

Protein
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.

Aminosalicylates

Aminosalicylates
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.

Amiodarone

Amiodarone
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
inhibitors

Inhibitors
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 blockers

ARBs
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
– SSRIs

Selective
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 post-synaptic neurons.
Examples include citalopram, sertraline, paroxetine and fluoxetine.

Drugs
that inhibit neuronal reuptake of serotonin and norepinephrine. Examples
include amitriptyline, nortriptyline and imipramine. Venlafaxine is a
non-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. H1
receptors, 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
post-synaptic 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.

Aspirin

Irreversible
inhibition of the cyclooxygenase enzyme.

Benzodiazepines

Enhance
binding of GABA to the GABA A receptor. Examples include diazepam, nitrazepam
and midazolam.

Beta-2
agonists

Examples
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-blockers

Examples
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.

Bisphosphonates

Examples
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 blockers

Examples
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.

Carbamazepine

Inhibition
of neuronal sodium channels. Carbamazepine is used to treat seizures,
trigeminal neuralgia and bipolar disorder.

Cephalosporins

Antimicrobial
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.

Clopidogrel

Irreversible
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.

Digoxin

Digoxin
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 conversation 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 at
D2 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
/ Gabapentin

Though
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
antagonists

Examples
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.

Heparins

Heparins
work by inhibiting thrombin and factor Xa in the final blood coagulation
pathway. LMWHs – such as enoxaparin and dalteparin – preferentially inhibit
facto Xa. Fondaparinux inhibits factor Xa only.

Insulin

Examples
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.

Iron

Replenish
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.

Lidocaine

Lidocaine
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.

Macrolides

Examples
include clarithromycin and erythromycin. Macrolides are protein synthesis
inhibitors – binding to the 50S subunit and blocking translocation.

Metformin

A
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.

Methotrexate

Methotrexate
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.

Metronidazole

An
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.

Naloxone

An
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.

Nitrofurantoin

An
antibacterial drug used to treat UTIs. Nitrofurantoin works by creating free
radicals that damages bacterial DNA.

NSAIDs

Non-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
/ Estrogens

Examples
include ethinylestradiol products and desogestrel. These drugs work in part
by suppressing LH/FSH release and, as a result, ovulation.

Opioids

Mu-opioid
receptor agonists used to treat pain. Examples include codeine, tramadol,
morphine and oxycodone.

Oxygen

Oxygen
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.

Acetaminophen

Acetaminophen
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.

Penicillins

Beta-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.

Phenytoin

Phenytoin
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
inhibitors

Examples
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
inhibitors

Examples
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.

Quinine

Originally
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.

Fluoroquinolones

Examples
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.

Statins

HMG-CoA
reductase inhibitors – the enzyme responsible for making cholesterol.
Examples include simvastatin, lovastatin and pravastatin.

Sulfonylureas

Examples
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.

Tetracyclines

Tetracyclines
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.

Thiazolidinediones

Also
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.

Trimethoprim

Trimethoprim
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.

Valproate

Valproate
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.

Vancomycin

An
antibacterial drug that works to treat Gram-positive infections.
Specifically, vancomycin works by inhibiting cell wall synthesis.

Warfarin

Wafarin
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.

Carbapenems

Examples
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.

Oxazolidinones

Examples
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
agents

Alkylating
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
inhibitors

MAO
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 inhibitors

Include
finaster 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.

Etanercept

Etanercept
is a DMARD that works as a decoy receptor for TNF. It is used for a wide
variety of autoimmune disorders.

Leflunomide

Leflunomide
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.

Taxanes

Taxanes
are chemotherapeutic drugs that include paclitaxel and docetaxel. Both drugs
inhibit microtubule formation, microtubules being fundamental to the process
of cell division.

Vinca
alkaloids

Vinca
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.

Fibrates

Fibrates
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.

Pyridostigmine

A
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.

Sevelamer

Sevelamer
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.

Lithium

Lithium
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.

Filgrastim

Filgrastim
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.

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.