BIOM 3090 Lecture Notes - Lecture 15: Vascular Resistance, Sympathomimetic Drug, Aqueous Humour
9 Jun 2018
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Adrenergic drugs
- many clinical applications and toxicities associated with adrenergic drugs
involve the cardiovascular system because
o SNS dominant system – involved in rapid regulation of blood pressure
(BP)
- Heart rate X stroke volume = cardiac output (CO)
- Vascular tone = peripheral vascular resistance (PVR)
o BP = CO x PVR
- 1) Sympathomimetic:
o mimic action of NE/epinephrine
▪ Direct: activate receptors directly (one or more subtypes,
depending on drug)
▪ Indirect: increase level of NE at synapse, therefore increase
activity at multiple receptor sub-types
- 2) Adrenergic antagonists
o receptor blockers
Sympathomimetic drugs (numbers refer to diagrams)
1. Presence of –OH groups = catecholamine
a. Absence of 1 or both –OH groups → decrease potency at adrenergic
receptors and decrease susceptibility to COMT
2. Addition of group at alpha-carbon = resistant to MAO
3. Addition of group on amino end alters receptor affinity
a. Larger groups: increase beta-receptor activity
b. Decrease alpha-receptor activity
Direct acting Sympathomimetic drugs
MIXED
Epinephrine
1=2, 1=2
MIXED
Norepinephrine
1=2, 1>>2
ALPHA
Phenylephrine
1>>2
ALPHA
Clonidine
1<<2
BETA
Dobutamine
1>2
BETA
Isoproterenol
1=2
BETA
Albuterol
1<<2
Organ system effects of adrenergic activation
- EYE
o 1 → contraction of dilator muscle = dilation of pupil (mydriasis)
o → decrease aqueous humor
find more resources at oneclass.com
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Document Summary
Many clinical applications and toxicities associated with adrenergic drugs: sns dominant system involved in rapid regulation of blood pressure (bp) Heart rate x stroke volume = cardiac output (co) Vascular tone = peripheral vascular resistance (pvr: bp = co x pvr. 1) sympathomimetic: mimic action of ne/epinephrine, direct: activate receptors directly (one or more subtypes, depending on drug) Indirect: increase level of ne at synapse, therefore increase activity at multiple receptor sub-types. 1<< 2: 1 contraction of dilator muscle = dilation of pupil (mydriasis, decrease aqueous humor, increase aqueous humor, aqueous humor produced by epithelium secreted into the eye, 1 increase hr/force of contraction. Blood vessels: 1 vasoconstriction (organs/skin, 2 vasodilation (skeletal muscles) Bp monitored by baroreceptors when bp changes, baroreceptors inflate reflex pathways for moment to moment regulation of bp. Baroreceptors sense decrease in bp message to cns to decrease: adrenergic drugs alter bp by altering co and/or pvr body tries to compensate.
