Vasoconstrictor agents

Vasoconstrictor agents

Dr. azher A. Auda
BDS CABS

vasoconstrictors

Chemical agent constrict blood vessels
Advantages of addition of V. To L A
1- Decrease blood flow to the site of injection
2- absorptionof L A to CVS is slowed
3- higher volumes of L A remain in and around the nerve longer period so increase duration of action
4- V. decrease bleading in the site of injection

Classification of vasoconsrictor

On the basis of mode of action ;
1- direct acting drugs; direct act on the adrenergic receptors.. Ex. Epinephrine , nor epinephrine
2 – indirect acting drugs; act by releasing nor epinephrine from the adrenergic nerve terminals
Ex. Tyramine ,amphetamine
3 – mixed acting drugs; have both direct and indirect action. Ex. ehpedrine


Types of vasocontrictors
Epinephrine( adrenaline
Most effective and most commonly used
Sources ; secreted from adrenal medulla. Its available as synthetic ,obtained from animals
Mode of acion; acts directly on both alpha and beta adrenergig receptors

Systemic action

1- cardiovascular system;…causes increase in systolic and diastolic BP, increased heart rate,stroke volume, cardiac output and O2 level
2 – respiratory system;… adrenaline is a potent dilator for smooth muscle of bronchiole so it’s the drug of choice for management oe acute asthma
3 – CNS ; ….usual dose of adrenaline will not potent CNS , CNS stimulation occurs in excessive dosage

Availabillity in dentistry

Adrenaline is the most potent and widely used vasoconsrictor in dentistry available in ;
1 : 50 000
1 : 80 000
1 : 100 000
1 : 200 000
dilution

Maximum dosage

This drug can produce undesirable results;
1 – if used in large volumes
2 – if injected I V
SO , for normal healthy adult Pt. the maximum recommended dose is 0.2 mg per appointment.
FOR Pt. with clinically significant cardiovascular disease the maximum dose is 0.04 mg per appointment


Nor epinephrene
Source either synthetic or obtained from adrenal medulla of animals
Mode of action act on alpha receptors
Systemic action
1 – cardiovascular system…increase systolic BP, stroke volume ,decrease heart rate,cardiac output
2 – respiratory system…not relax smooth muscle
3 – CNS usual dose not potent CNS stimulant

Availability in dentistry

Used with L A as vasoconstrictor in
1: 300 000 dilution
Maximum recommended dose for normal healthy adult Pt. is 0.34 mg per appointment.
For Pt. with clinically significant cardiovascular disease is 0.14 mg per appointment

Levonordifrine

- synthetic substance act on alpha receptor
- produces less cardiac and CNS stimulation than epinephrene
- its mainly used with mepivacaine in a
1 :20 000 dilution
- max. dose for all Pt. should be 1 mg per appointment


Felypressine
Source .. Synthetic from anti diuretic hormone.
Mode of action ..direct stimulant of vascular smooth muscle.
Heart …no direct effect
Blood vessel ..high doses causes consriction of cutaneous blood vessel
CNS no effect
Uterus it has oxytocic action ,so never used in pregnancy

Selection of vasoconstriction

The selection of an appropriate vasoconstrictor is based on the following factors
1 – length of surgical or dental procedure
2- need for hemostasis during surgery
3- need for postoperative pain control
4 – medical or physical status of the Pt. and if used any medications

Contraindication

The following group of Pt.
1 – Pt. with cardiovascular disease such as ischemic heart disease,hypertension,cerebral strokes
2 – Pt. with uncontrolled non cardiovascular disease such as thyrotoxicosis
3- Pt. receiving monoamine – oxidase inhibitors , tricyclic antidepressant


Reducing agent
Vasoconstrictors in L A are unstable and maybe oxidize if exposed to sunlight and lead to brown discoloration of solution.
Sodium bisulphate is added to the cartriges to prevent this condition

Preservative

Chemicals are used as a general preservatives these are added to increase the shelf – life of L A
1 – methylparaben
2- thymol

Fungicide

Small quantity of thymole is added to seve as a fungicidal
Sodium chloride or ringers solution added to L A to make the sol. Isotonic with the tissue and prevent the discomfort during injection
Distilled water
Used as a diluents to provide the volume of solution in the dental cartrige