Name Class Clinical Indications Receptor Action Mechanism of Action Adverse Effects and Interactions Administration + PK
When histamine binds to H1 receptors on vascular endothelial cells, it activates the Gq second messenger
Allergic reactions system causing the release of vasoactive molecules such as nitric oxide and prostacyclin This causes
Chlorphenamine vasodilation, leading to increased vascular permeability. Histamine also binds to H1 receptors in smooth
1st Generation Anaphylaxis H1 Receptor inverse
Promethazine muscle activating the Gq second messenger system causing increased intracellular calcium and therefore Can cause drowsiness Oral
antihistamines Sedation agonist smooth muscle constriction. Antihistamines act as H1 receptor inverse agonists, binding to the receptor and
Cyclizine
Nausea stabilizing it in its inactive state. 1st generation antihistamines can also cross the blood brain barrier causing
sedation and anti nausea effects.
Antihistamines
When histamine binds to H1 receptors on vascular endothelial cells, it activates the Gq second messenger
Allergic reactions system causing the release of vasoactive molecules such as nitric oxide and prostacyclin This causes
Cetirizine 2nd Generation H1 Receptor inverse vasodilation, leading to increased vascular permeability. Histamine also binds to H1 receptors in smooth
Anaphylaxis muscle activating the Gq second messenger system causing increased intracellular calcium and therefore
Cannot cross BBB so doesn’t cause drowsiness Oral
Loratadine antihistamines agonist
Insect bites smooth muscle constriction. Antihistamines act as H1 receptor inverse agonists, binding to the receptor and
stabilizing it in its inactive state.
Agonises beta 2 receptors in the bronchial smooth muscle. This activates the Gs second messenger system,
Short acting beta 2 Acute exacerbations of Short acting beta 2 Tachycardia, skeletal muscle tremors and
Salbutamol causing increased production of cAMP. cAMP activates protein kinase A which causes a reduction in cytosolic
hyperglycaemia
Inhalation, IV in emergency
agonist (SABA) asthma and COPD adrenergic agonist Ca2+. This decrease in Ca2+ causes smooth muscle relaxation and therefore bronchodilation.
Prevention of asthma and Agonises beta 2 receptors in the bronchial smooth muscle. This activates the Gs second messenger system,
causing increased production of cAMP. cAMP activates protein kinase A which causes a reduction in cytosolic
Salmeterol Long acting beta 2 COPD exacerbations Long acting beta 2 Tachycardia, skeletal muscle tremors and
Ca2+. This decrease in Ca2+ causes smooth muscle relaxation and therefore bronchodilation. They also Inhalation
Formoterol agonist (LABA) Only used in combination adrenergic agonist hyperglycaemia
contain a long lipophilic side chain which anchors them to the phospholipid membrane of the cell. This allows
with inhaled corticosteroids for repeated binding and unbinding resulting in a long acting effect
Non selective Second line drug for Antagonises M3 receptors in the bronchial smooth muscle, inhibiting the Gq second messenger system which
Ipratropium bromide M1, M2 and M3 receptor would usually cause activation of phospholipase C, which would increase production of IP3 and DAG leading Tachycardia, nausea, blurred vision, dry mouth,
Bronchodilators muscarinic prevention of COPD to increased intracellular calcium. By blocking this process, lowered intracellular calcium causes smooth urinary retention and constipation
Inhalation
Tiotropium antagonist
antagonist exacerbations muscle relaxation which is seen as bronchodilation.
Aminophylline Inhibits phosphodiesterase III which usually acts to hydrolyse cAMP. However, as it is inhibited, cAMP is no
(2:1 complex of Prevention of asthma and Phosphodiesterase III longer hydrolysed so levels of cAMP rise. This increase in cAMP activates protein kinase A which causes a Very narrow therapeutic window
Methylxanthine reduction in cytosolic Ca2+. This decrease in Ca2+ causes smooth muscle relaxation and therefore Tachycardia, arrhythmias, and hypertension
Oral
theophylline and COPD exacerbation inhibitor
ethylenediamine) bronchodilation.
Antagonises cysLT1 receptors on bronchial smooth muscle. This inhibits the Gq second messenger system
Leukotriene receptor Prevention of asthma and CysLT1 receptor which would usually cause activation of phospholipase C, which would increase production of IP3 and DAG
Montelukast leading to increased intracellular calcium. By blocking this process, lowered intracellular calcium causes
Fever, gastro discomfort, nausea and headache Oral
antagonist (LTRA) COPD exacerbation antagonist
smooth muscle relaxation which is seen as bronchodilation.
