Sympathomimetics Flashcards
Describe the PNS
pre and post ganglionic fibres
pre-ganglionic from:
CN III, VII, IX, X (eye, salivary glands, heart, bronchi, upper GI (splenic flexure) and ureters)
S2,3,4: (bowel, bladder, genitals)
myelinated
AcH: nicotinic receptor
Modulated by anticholinergics and anticholinesterases
Describe the SNS
T1-L2 : ant primary rami via white rami communicants into sympathetic chain. Sympathetic chain or ganglia may synapse at adjacent level or pass ant through a splanchnic nerve to synapse in prevertebral ganglion.
Unmyelinated post ganglion fibres into adjacent spinal nerves via grey rami communicans. Norad
Describe the actions of sympathomimetics
Act via adrenoreceptors or dopamine receptors
Direct or indirect
based on a benzene ring with various side chains at C1
Hydroxyl group at C3, C4 called catecholamine
Describe adrenaline
Naturally occuring catecholamine
Clear colourless solution
0.1-1mg.ml
Bolus in anaphylaxis, infusion (dose 0.01-0.5Ug.kg.min)
1 in 200,000 LA
Mechanism:
A and B
A1 phospholipase C (via Gq)
A2 (Gs)
Effects:
CVS: low dose B high dose A
Resp: increase MV. PVR increased
Met: increase BMR. Increased Na reabsorption (renin). Increased K due to K release from liver
CNS: increase MAC
renal: reduced blood flow, increase bladder tone
Kinetics:
not given orally
tracheal erratic
metabolised by mitochondrial MAO and COMT to VMA. conjugated. excreted in urine
