Core pharmacology

Class Group

ADRENERGIC

Legacy Cicm Level

Level 1

Introduction

Is a naturally occurring catecholamine released in post ganglionic SNS, medulla (20:80 Adr)

Indications Uses

Used to treat hypotension due to decreased SVR

Presentation

injectable solution only, 1mg/mL in 2 mL vials diluted in 5D or NS.
CVC only due to risk of extravasation associated necrosis

Main Action

Alpha and beta adrenergic receptor activity

Mechanism of action

- Acts primarily directly at alpha-1-adrenoreceptors (phospholipase C → IP3 → increased calcium)
- To a lesser extent acts on beta 1>beta 2 effects

Physiological effects

Low doses: β - ↑ino+chronotropy
increased MVO2
Higher doses: 1 -
peripheral vasocontriction.
↑systolic/diastolic pressures
may cause reflex bradycardia

Detail:
CVS
- Increased SVR leading to increased SBP/DBP/MAP
- Increased afterload - leading to increased myocardial oxygen consumption, slight decrease in cardiac output and may lead to reflex bradycardia (through beta-1 effects limit this)
- Coronary artery vasodilation increased coronary O2 delivery
- Pulmonary vascular resistance is increased
- Excessive doses may lead to limb or organ ischaemia
- Extravasation may lead to tissue necrosis

CNS
- Generally improves cerebral blood flow by way of improved CPP more than it decreases CBF by cerebral vasoconstriction

Renal/GU
- Decreases renal blood flow
- Causes uterine constriction (may lead to fetal asphyxia)

GIT:
- Decreased splanchnic blood flow

Metabolic
- Less hyperglycaemia/acidosis, although it may decrease insulin secretion

Adverse Effects Toxicity

Excessive doses cause severe hypertension
Reduced flow to organs
splanchnic
renal
Issues with increased MVO2 and IHD

Absorption

IV only
Clear Solution 1:1000
8-12 mcg/min uptitrated to effect
onset / duration immediate / 1-2 minutes

Distribution

doesn’t cross the BBB

Metabolism

Rapidly metabolised into adrenaline by MAO (Uptake 1, Nv terminal)
COMT (Uptake 2 circulation)

25% removed in the lungs

Excretion

urine as inactive metabolites (84-96%)

Half-life

2 minutes

Route And Dose

IV infusion- 0.05-0.5mcg/kg. Through a central line diluted with glucose or saline.