Ipratropium

UNDER REVIEW (September 2016)

Mechanism of Action:

Ipratropium is an antagonist at muscarinic acetylcholine receptors (mAChR)(m3 subtype). Muscarinic AChRs are transmembrane G-protein coupled receptors (GPCRs) which are activated by the endogenous neurotransmitter, acetylcholine, the key transmitter in the parasympathetic nervous system, and also a major transmitter in the CNS. Another well-known muscarinic antagonist is atropine.

Lecture and CAL materials:

Theophylline

UNDER REVIEW (September 2016)

Mechanism of Action:

Theophylline is a xanthine derivative drug that has a structural and pharmacological similarity to caffeine. It is naturally found in black tea and green tea. The mechanism of action is probably by inhibition of phosphodiesterase (PDE), an enzyme that breaks down the secondary messenger cyclicAMP. Potentiation of cAMP, the secondary messenger for beta-adrenoreceptors, leads to smooth muscle relaxation. Some of the effects of theophylline are therefore similar to beta-agonists. The main actions of theophylline are (1) relaxation of bronchial smooth muscle, (2) positive inotropic – increases heart muscle contractility and efficiency(3) positive chronotropic – increases heart rate, (4) lowers blood pressure, (5) increases renal blood flow, and (6) some anti-inflammatory effect. Theophylline may also antagonise the effects of adenosine.

Lecture and CAL materials:

Salbutamol

UNDER REVIEW (September 2016)

Mechanism of Action:

Salbutamol is a short acting beta-2 adrenoceptor agonist. Activation of beta-2 receptors relaxes bronchial smooth muscle, relaxes myometrial smooth muscle in uterus, causes tremor of skeletal muscle and tends to stimulate uptake of potassium into cells. Beta-2 receptors (transmembrane G-protein coupled receptors) are normally activated by circulating adrenaline (hormone, released from adrenal medulla). Salbutamol is not entirely specific and has slight cross-reactivity with beta-1 adrenoceptors leading to tachycardia and increased force of cardiac contraction (generally only seen with very high doses). Beta-2 receptors also mediate vasodilatation, glycogenolysis, lipolysis and are found on cells of the immune system.

Lecture and CAL materials: