2. Nicotinic antagonists (n-cholinoblockers)

Compose of two drug groups: ganglion-blocking drugs and neuromuscular blocking drugs.

2. 2. 1. Ganglion-blocking drugs

List of drugs

Azamethonium bromide

Mechanism of action

Noncompetitive blockage of N-cholinoreceptors of autonomic ganglions

Pharmacological effects

Opposite effect if compared to previous topic:

Blockage of N-cholinoreceptors

Autonomic ganglions

Dilation of blood vessels

Indications

1. Relieving of hypertensive crises:

Azamethonium → dilation of blood vessels (arteries) → decreasing of arterial pressure → relieving of hypertensive crises

2. Relieving of acute pulmonary oedema:

Azamethonium → dilation of blood vessels (veins) → decreasing of venous blood return to the heart → relieving of acute pulmonary oedema

2. Neuromuscular blocking drugs (myorelaxants)

List of drugs

Non-depolarising blockers: pipecuronium bromide

Depolarising blockers: suxamethonium

Mechanism of action

Competitive blockage of N-cholinoreceptors of skeletal muscles.

Pharmacological effects

Opposite effect if compared to previous topic:

Blockage of N-cholinoreceptors

Skeletal muscles

Relaxation

Indications

1. Relaxation of skeletal muscles during abdominal surgery

- relaxation of vocal ligaments → facilitation of intubation (inserting specific tube to upper airways to allow general anaesthesia)

- relaxation of skeletal muscles of the body → prevention of any motion of patients during surgery

- in more highest dosages these drugs can also relax a diaphragm, that gives the opportunity to apply to the patient artificial ventilation.

Some aspects of physiology. VERY IMPORTANT!!!

Adrenergic synapses (most of them are sympathetic synapses), as any another synapses in the organism, consist of two parts: presynaps and postsynaps. Presynaps releases norepinephrine, which activates α₁, α₂, β₁, β₂-adrenoreceptors on the postsynaptic membrane. Thereafter norepinephrine is destroyed by specific enzyme – catechol-O-methyltransferase (COMT), which is located on the postsynaptic membrane.

Norepinephrine produces next effects (see and study the table):

Type of receptors	Organ	Effect
Stimulation of α1- adrenoreceptors	Eye	Dilation of pupil (midriasis)
	Blood vessels	Constriction (due to contraction of smooth muscles of blood vessels)
Stimulation of α2- adrenoreceptors	Blood vessels	Constriction (due to contraction of smooth muscles of blood vessels)
Stimulation of β1- adrenoreceptors	Heart	Increasing of heart rate, heart contractility, heart conductance and heart excitability
Stimulation of β2- adrenoreceptors	Bronchi	Dilation (due to relaxation of smooth muscles of bronchi)
	Uterus	Relaxation (due to relaxation of smooth muscles of uterus)
	Mast cells	Inhibition of degranulation (i.e. inhibition of releasing of histamine from mast cells)