1. Vasoconstrictors
Originally added to reduce systemic uptake in an attempt to limit toxicity.
Prolong the duration
Produces profound anaesthesia.
Reduce operative bleeding.
Two types:
Sympathomimetic naturally occurring.
Synthetic polypeptides, Felypressin

2. Vasoconstrictors Epinephrine: (Adrenaline) Uses in dentistry:
Local anaesthetic solution.
Gingival retraction cords.
In the ER as life-saving drug in anaphylaxis.
Mechanism of action:
Interact with adrenergic receptors in the vessels
α1 & α2 producing vasoconstriction in skin & MM
β2 stimulation causing vasodilatation in skeletal muscles.

3. Vasoconstrictors Epinephrine
Metabolism:
Appears very rapidly in the systemic circulation !!!
Exogenously administered epinephrine is metabolized extraneuronal and 1% is excreted in the urine unchanged.
Dosage:
1:80,000 is the commonest dose used, µg/ml

4. Vasoconstrictors Epinephrine
Systemic effect:
Being a naturally occurring hormone, it exert a number of physiological responses on the different systems.
The heart:
Has direct and indirect action.
Direct action on β1 receptors increases the rate and force of contraction raising cardiac output.
Indirect action, increase pulse and cardiac output, lead to rise in systolic blood pressure, (not with dental dose)

5. Vasoconstrictors Epinephrine
Blood vessels:
Contain α1, α2 and β2 adrenoreceptors in the vessels of the skin, mucous membrane and skeletal muscles.
α1 receptors causes vasoconstriction since they are susceptible to endogenous nor-epinephrine and exogenous epinephrine. Reduce operative bleeding

6. Vasoconstrictors Epinephrine
α2 receptors are only susceptible to circulating epinephrine.
β2 found in the skeletal muscles, and very uncommon in the skin and mucous membrane. β2 stimulation result in vasodilatation, lowering peripheral resistance and a fall in the diastolic blood pressure. (with dental dose)

7. Vasoconstrictors Epinephrine
Haemostasis:
The vasoconstricting effect.
Adrenaline promote platelets aggregation in the early stages.
Fibrinolytic activity compromise clot stability.
Lungs:
Stimulation of β2 receptors in the lung lead to bronchial muscle relaxation, life-saving in bronchial (spasm) constriction during anaphylactic reaction.
Wound healing:
Reduced local tissue oxygen tension.
Epinephrine-induced fibrinolysis.

8. Vasoconstrictors Felypressin: Dose:
It is an analogue of the naturally occurring Vasopressin.
Bind to vasopressin V1 receptor in the vascular smooth muscle producing vaso-constriction and reduce local blood flow.
Less potent than the catecholamines &poorer control of bleeding during operative procedures.
Acts on the venous side rather than the arterial side.
Dose:
0.03 IU/ml (0.54 µg/ml)