SECTION 6 Pharmacology

Drug classes 286

A–Z of drugs 289

Prescription abbreviations 316

Further reading 316

Drug classes

ACE inhibitors

Angiotensin-converting enzyme (ACE) inhibitors allow blood vessels to dilate by preventing the formation of angiotensin II, a powerful artery constrictor. Used in the treatment of heart failure, hypertension, diabetic nephropathy and post-myocardial infarction.

Analgesics

Used to relieve pain and can be divided into opioids and non-opioids.

Opioids block transmission of pain signals within the brain and spinal cord. They include morphine and pethidine and are used to treat moderate to severe pain arising from surgery, serious injury and terminal illness.

Non-opioids are less powerful and work by blocking the production of prostaglandins, thereby preventing stimulation of nerve endings at the site of pain. They include paracetamol and non-steroidal anti-inflammatory drugs such as aspirin.

Antibiotics

Used to treat bacterial disorders ranging from minor infections to deadly diseases. Antibiotics work by destroying the bacteria or preventing them from multiplying while the body’s immune system works to clear the invading organism. There are different classes of antibiotic, which include penicillins (amoxicillin, ampicillin, benzylpenicillin), cephalosporins (cefaclor, cefotaxime, cefuroxime), macrolides (erythromycin), tetracyclines (oxytetracycline, tetracycline), aminoglycosides (gentamicin) and glycopeptides (vancomycin).

Antiemetics

Act by blocking signals to the vomiting centre in the brain which triggers the vomiting reflex. Used to prevent or treat vomiting and nausea caused by motion sickness, vertigo, digestive tract infection and to counteract the side-effects of some drugs.

Antiepileptics

Used to prevent or terminate epileptic seizures. There are several types of epilepsy, each treated by a specific antiepileptic medication. It is therefore essential to classify the type of seizure in order to treat it effectively and minimize side-effects.

Antiretrovirals

Specific antiviral drugs for the treatment of infection caused by the human immunodeficiency virus (HIV). There are two groups:

Reverse transcriptase inhibitors reduce the activity of the reverse transcriptase enzyme, which is vital for virus replication. They are divided according to their chemical structure into nucleoside and non-nucleoside inhibitors.

Protease inhibitors interfere with the protease enzyme.

To reduce the development of drug resistance the drugs are used in combination. Treatment is usually initiated with a combination of two nucleoside reverse transcriptase inhibitors (NRTI) plus a non-nucleoside reverse transcriptase inhibitor (NNRTI) or a protease inhibitor (often referred to as ‘triple therapy’). Antiretrovirals are not a cure for HIV but they increase life expectancy considerably. However, they are toxic and treatment regimens have to be carefully balanced.

β-blockers

Prevent stimulation of the β-adrenoreceptors in the heart muscle (mainly β₁-receptors) and peripheral vasculature, bronchi, pancreas and liver (mainly β₂-receptors). Used to treat hypertension, angina, myocardial infarction, arrhythmias and thyrotoxicosis. Can also be used to alleviate some symptoms of anxiety. Since blocking β-adrenoreceptors in the lungs can lead to constriction of air passages, care needs to be taken when treating patients with asthma or COPD.

Benzodiazepines

Increase the inhibitory effect of gamma-aminobutyric acid (GABA), which depresses brain cell activity in the higher centres of the brain controlling consciousness. Used for anxiety, insomnia, convulsions, sedation for medical procedures and alcohol withdrawal.

Bronchodilators

Dilate the airways to assist breathing when constricted or congested with mucus. There are two main types:

Sympathomimetics (e.g. salbutamol) stimulate β₂-adreno-receptors on the surface of bronchial smooth muscle cells causing the muscle to relax.

Anticholinergics (e.g. ipratropium bromide) act by blocking the neurotransmitters that trigger muscle contraction.

Both are used to treat asthma and other conditions associated with reversible airways obstruction such as COPD.

Calcium channel blockers

Interfere with the transport of calcium ions through the cell walls of cardiac and vascular smooth muscle. Reduce the contractility of the heart, depress the formation and conduction of impulses in the heart and cause peripheral vasodilation. Used to treat angina, hypertension and arrhythmias.

Corticosteroids

Reduce inflammation by inhibiting the formation of inflammatory mediators, e.g. prostaglandins. Used to control many inflammatory disorders thought to be caused by excessive or inappropriate activity of the immune system, e.g. asthma, rheumatoid arthritis, lupus, eczema, as well as inflammation caused by strain and damage to muscles and tendons. Also known as glucocorticoids.

Diuretics

Work on the kidneys to increase the amount of sodium and water excreted. There are different types of diuretic that work on the nephron:

Thiazides (bendroflumethiazide/bendrofluazide)

Loop (furosemide/frusemide, bumetanide)

Potassium-sparing (amiloride, spironolactone)

Osmotic (mannitol)

Carbonic anhydrase inhibitors (acetazolamide, dorzolamide)

Used to treat hypertension (thiazides), chronic heart failure and oedema (loop diuretics, thiazides or a combination of both), glaucoma (carbonic anhydrase inhibitors or osmotic), raised intracranial pressure (osmotic).

Inotropes

Work by increasing the contractility of the heart muscle. They can be divided into three groups:

Cardiac glycosides (e.g. digoxin) assist activity of heart muscle by increasing intracellular calcium storage in myocardial cells. Used for heart failure and supraventricular arrhythmias.

Sympathomimetics (e.g. dobutamine, dopamine) stimulate β₁-receptors on the heart which increase the rate and force of myocardial contraction. Provide inotropic support in infarction, cardiac surgery, cardiomyopathies, septic shock and cardiogenic shock.

Phosphodiesterase inhibitors (e.g. milrinone) inactivate cyclic AMP, which increases the force of myocardial contraction and relaxes vascular smooth muscle. Used to treat congestive heart failure.

Mucolytics

Reduce the viscosity of bronchopulmonary secretions by breaking down their molecular complexes. Used to treat excessive or thickened mucus secretions.

Non-steroidal anti-inflammatory drugs (NSAIDs)

Inhibit the production of prostaglandins, which are responsible for inflammation and pain following tissue damage. They are called non-steroidals to distinguish them from corticosteroids, which have a similar function. Used for inflammatory diseases, pain and pyrexia.

A–Z of drugs

Acetylcysteine (mucolytic)

Reduces the viscosity of secretions associated with impaired or abnormal mucus production. Administered with a bronchodilator as it can cause bronchospasm and inhibit ciliary function. Also used as an antidote for paracetamol overdose.

Side-effects: bronchoconstriction, nausea and vomiting.

Aciclovir (antiviral)

Used against infections caused by herpes virus (herpes simplex and varicella zoster).

Side-effects are rare.

Adenosine (anti-arrhythmic)

Reverses supraventricular tachycardias to sinus rhythm.

Side-effects: chest pain, dyspnoea, nausea, bronchospasm, facial flush.

Adrenaline/epinephrine (sympathomimetic agent)

Used during cardiopulmonary resuscitation to stimulate heart activity and raise low blood pressure. Adrenaline (epinephrine) acts as a vasoconstrictor and is used to reduce bleeding and prolong the effects of local anaesthetic. It is also used to treat anaphylactic shock as it raises blood pressure and causes bronchodilation. Since it lowers pressure in the eye by decreasing production of aqueous humour it is used for glaucoma and eye surgery.

Side-effects: dry mouth, anxiety, restlessness, palpitations, tremor, headache, blurred vision, hypertension, tachycardias.

Alendronate (bisphosphonate)

Inhibits the release of calcium from bone by interfering with the activity of osteoclasts, thereby reducing the rate of bone turnover. Used in the prophylaxis and treatment of postmenopausal osteoporosis and corticosteroid-induced osteoporosis. Often used in conjunction with calcium tablets. Also used in the treatment of Paget’s disease, hypercalcaemia of malignancy and in bone metastases in breast cancer.

Side-effects: oesophageal irritation and ulceration, gastrointestinal upset, increased bone pain in Paget’s disease.

Alfentanil (opioid analgesic)

Fast-acting, it is used as a respiratory depressant in patients needing prolonged assisted ventilation. Also used as an analgesic during surgery and to enhance anaesthesia.

Side-effects: drowsiness, nausea, vomiting, constipation, dizziness, dry mouth.

Allopurinol (anti-gout)

A prophylactic for gout and uric acid kidney stones.

Side-effects: rash, itching, nausea.

Aminophylline (xanthine)

Acts as a bronchodilator and is used for reversible airways obstruction and intravenously for acute severe asthma.

Side-effects: tachycardias, palpitations, nausea, headache, insomnia, arrhythmias, convulsions.

Amiodarone (anti-arrhythmic)

Slows nerve impulses in the heart muscle. Used to treat ventricular and supraventricular tachycardias and prevent recurrent atrial and ventricular fibrillation.

Side-effects: photosensitivity, reversible corneal depositions, liver damage and thyroid disorders.

Amitriptyline (tricyclic antidepressant)

Used as a long-term treatment for depression, particularly when accompanied by anxiety or insomnia, owing to its sedative properties. In low doses it is also useful for the treatment of neuropathic pain. It is also sometimes used to treat nocturnal enuresis (bedwetting) in children.

Side-effects: drowsiness, sweating, dry mouth, blurred vision, dizziness, fainting, palpitations, gastrointestinal upset.

Amlodipine (calcium channel blocker)

Used to treat hypertension and angina. Can be used safely by asthmatics and non-insulin-dependent diabetics.

Side-effects: oedema, headache, dizziness, fatigue, sleep disturbances, palpitations, flushing, gastrointestinal upset.

Amoxicillin (penicillin antibiotic)

See antibiotics in ‘Drug classes’.

Ampicillin (penicillin antibiotic)

See antibiotics in ‘Drug classes’.

Aspirin (NSAID)

Used as an anti-inflammatory, as an analgesic and to reduce fever. It also inhibits thrombus formation and is used to reduce the risk of heart attacks and stroke.

Side-effects: gastric irritation leading to dyspepsia and bleeding, and wheezing in aspirin-sensitive asthmatics.

Atenolol (β-blocker)

Used to treat hypertension, angina and arrhythmias.

Side-effects: muscle ache, fatigue, dry eyes, bradycardia and atrioventricular (AV) block, hypotension, cold peripheries.

Atorvastatin (statin)

Lowers low-density lipoprotein (LDL) cholesterol and is prescribed for those who have not responded to diet and lifestyle modification to protect them from cardiovascular disease.

Side-effects: mild: gastrointestinal upset, headache, fatigue, rarely myositis.

Atracurium (non-depolarizing muscle relaxant)

Used as a muscle relaxant during surgery and to facilitate intermittent positive pressure breathing in intensive care unit.

Side-effects: skin rash, flushing, hypotension.

Atropine (antimuscarinic)

Relaxes smooth muscle by blocking the action of acetylcholine and is used to treat irritable bowel syndrome. Can be used to paralyse ciliary action and enlarge the pupils during eye examinations. Also used to reverse excessive bradycardia, in cardiopulmonary resuscitation and for patients who have been poisoned with organophosphorous anticholinesterase drugs.

Side-effects: blurred vision, dry mouth, thirst, constipation, flushing, dry skin.

Azathioprine (immunosuppressant)

Prevents rejection of transplanted organs by the immune system and in a number of autoimmune and collagen diseases (including rheumatoid arthritis, polymyositis, systemic lupus erythematosus).

Side-effects: nausea, vomiting, hair loss, loss of appetite, bone marrow suppression.

Baclofen (skeletal muscle relaxant)

Acts on the central nervous system to reduce chronic severe spasticity resulting from a number of disorders, including multiple sclerosis, spinal cord injury, brain injury, cerebral palsy or stroke.

Side-effects: drowsiness, nausea, urinary disturbances.

Beclometasone (corticosteroid)

Given by inhaler and used to control asthma in those who do not respond to bronchodilators alone. Also used in creams to treat inflammatory skin disorders and to relieve and prevent symptoms of vasomotor and allergic rhinitis.

Side-effects: cough, nasal discomfort/irritation, hoarse voice, sore throat, nosebleed (with inhalers/nasal spray).

Bendroflumethiazide/bendrofluazide (thiazide diuretic)

Used to treat hypertension, cardiac failure and resistant oedema. Also reduces urinary calcium excretion and so decreases rate of recurrence in patients with recurrent renal stones.

Side-effects: hypokalaemia, dehydration, postural hypotension, gout and hyperglycaemia.

Benzylpenicillin (penicillin antibiotic)

See antibiotics in ‘Drug classes’.

Budesonide (corticosteroid)

Used as an inhaler in the prophylactic treatment of asthma and COPD. Also given systemically in a controlled-release form for Crohn’s disease.

Side-effects: nasal irritation, cough, sore throat.

Calcitonin (salmon)/salcatonin (hormone)

Regulates bone turnover and is used to treat hypercalcaemia in Paget’s disease of bone and metastatic cancer. Also given for prophylaxis and treatment of osteoporosis and for short-term pain relief following vertebral fracture or in metastatic disease.

Side-effects: gastrointestinal upset, flushing.

Captopril (ACE inhibitor)

Reduces peripheral vasoconstriction and is used to treat hypertension, congestive heart failure, post-myocardial infarction and diabetic nephropathy.

Side-effects: postural hypotension, persistent dry cough, rash, loss of taste, reduced kidney function.

Carbamazepine (anticonvulsant)

Used to reduce likelihood of generalized tonic-clonic seizures and partial seizures. Also used to relieve severe pain in trigeminal neuralgia and for prophylaxis of bipolar disorder.

Side-effects: drowsiness, ataxia, blurred vision, confusion, nausea, loss of appetite.

Cefaclor (cephalosporin antibiotic)

See antibiotics in ‘Drug classes’.

Cefotaxime (cephalosporin antibiotic)

See antibiotics in ‘Drug classes’.

Cefuroxime (cephalosporin antibiotic)

See antibiotics in ‘Drug classes’.

Celecoxib (NSAID)

Used to relieve the symptoms of osteoarthritis and rheumatoid arthritis. Has a relatively selective action on the inflammatory response compared to other NSAIDs, causing fewer gastrointestinal disturbances. However, it also associated with a greater risk of adverse cardiovascular effects.

Side-effects: dizziness, fluid retention, hypertension, headache, itching, insomnia.

Chlorpromazine (antipsychotic)

Has a sedative effect and is used to control the symptoms of schizophrenia and to treat agitation without causing confusion and stupor. Also used to treat nausea and vomiting in terminally ill patients.

Side-effects: extrapyramidal symptoms (e.g. parkinsonian symptoms, dystonia, akathisia, tardive dyskinesia), hypotension, dry mouth, blurred vision, urinary retention, constipation, jaundice.

Ciclosporin (immunosuppressant)

Used to prevent rejection of organ and tissue transplantation. Also used to treat rheumatoid arthritis, and severe resistant psoriasis and dermatitis when other treatments have failed.

Side-effects: nephrotoxicity, hypertension, increased body hair, nausea, tremor, swelling of gums.

Cimetidine (anti-ulcer – H₂-receptor antagonist)

Decreases gastric acid production and is used to treat gastric and duodenal ulcers, and for gastro-oesophageal reflux disease.

Side-effects: none.

Ciprofloxacin (antibacterial)

Treats mainly Gram-negative infection and some Gram-positive infections. Used for chest, intestine and urinary tract infections and to treat gonorrhoea.

Side-effects: nausea, vomiting, abdominal pain, diarrhoea.

Clomipramine (tricyclic antidepressant)

Used for long-term treatment of depression, especially when associated with phobic and obsessional states.

Side-effects: drowsiness, sweating, dry mouth, blurred vision, dizziness, fainting, palpitations, gastrointestinal upset.

Clonidine (α₂-adrenoceptor agonist)

Acts centrally to reduce sympathetic activity and thereby reduces peripheral vascular reactivity. Used in the prophylaxis of migraine and in the treatment of menopausal flushing. Sometimes used to treat hypertension.

Side-effects: gastrointestinal upset, dry mouth, headache, dizziness, rash, sedation, nocturnal unrest, depression, bradycardia, fluid retention.

Codeine phosphate (opioid analgesic)

A mild opioid analgesic that is similar to, but weaker than, morphine. Used to treat mild to moderate pain and is often combined with a non-opioid analgesic such as paracetamol (to form co-codamol). Also used as a cough suppressant and for the short-term control of diarrhoea.

Side-effects: constipation.

Dexamethasone (corticosteroid)

Suppresses inflammatory and allergic disorders. Used to diagnose Cushing’s disease. Used to treat cerebral oedema, congenital adrenal hyperplasia, nausea and vomiting associated with chemotherapy and various types of shock.

Side-effects: indigestion, acne, increased body hair, moon-face, hypertension, weight gain/oedema, impaired glucose tolerance, cataract, glaucoma, osteoporosis, peptic ulcer, candida.

Diazepam (benzodiazepine)

Has a wide range of uses. Most commonly used to reduce anxiety, relax muscles, promote sleep and in the treatment of alcohol withdrawal. Also used for febrile convulsions and status epilepticus.

Side-effects: daytime drowsiness, dizziness, unsteadiness, confusion in the elderly. Dependence develops with prolonged use.

Didanosine (ddI) (antiretroviral – NRTI)

Prevents the replication of HIV and therefore the progression of AIDS by blocking the action of the reverse transcriptase enzyme. Usually used in combination with other antiretroviral drugs.

Side-effects: pancreatitis, peripheral neuropathy, headache, insomnia, gastrointestinal upset, fatigue, breathlessness, cough, blood disorders, rash, liver damage.

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