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Vasoconstrictors

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. Vasoconstrictors.

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Vasoconstrictors

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  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. VasoconstrictorsEpinephrine • 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, 12.5 µg/ml

  4. VasoconstrictorsEpinephrine • 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. VasoconstrictorsEpinephrine • Blood vessels: • Contain α1,α2andβ2 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. VasoconstrictorsEpinephrine • α2receptors 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. VasoconstrictorsEpinephrine • 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: • 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)

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