Pain Control Lect 3

Front 1

What makes local anesthetics different from other drugs used in med and dentistry?

Back 1

LA cease to provide their clinical effect when absorbed in circulation whereas other drugs must enter this.

Front 2

What effect do most LAs produce? What LA is the most potent?

Back 2

All produce some degree of vasoactivity, most producing vasodilation.

Procaine - most potent vasodilator.
cocaine - only LA that produces vasoconstriction

Front 3

What is the first pass effect for the oral route?

Back 3

50 to 90% of the absorbed drug is metabolized on the first pass through the liver.

Front 4

Describe the different absorption and uptake via topical route
1. Tracheal mucosa
2. Intact skin
3. IV

Back 4

Local anesthetics are absorbed at differing rates after the application to membranes.
Tracheal mucosa, uptake is almost as rapid as IV administration.
Applied to intact skin, they do not have an anesthetic action.
Eutectic mixture of local anesthetics(EMLA) has been develop to provide surface anesthesia for intact skin


IV administration provides the most rapid elevation of blood levels and is used in the primary treatment of ventricular disrhythmias.

Front 5

What does the blood level of LA depends on?

Back 5

rate of absorption into CVS
rate of distribution
elimination of the drug


Note: all LA cross the blood brain barrier and the placenta.

Front 6

Describe the biotransformation of esters

Back 6

Ester local anesthetics are hydrolyzed in the plasma by the enzyme pseudocholinesterase.

Procaine hydrolyzed to PABA. Some is converted into diethylamino alcohol and excreted; some is excreted unchanged in urine.

atypical pseudocholinesterase - inability to hydrolyze ester local anesthetics. occurs in 1/ 2800 people.

Front 7

Biotransformation of amide

Back 7

The primary site of biotransformation of amide drugs is the liver.
Amides have a more complex process of biotransformation. Amides are usually present as the parent compound in greater percentage than esters.

Front 8

What does slower than normal biotransformation lead to?

Back 8

Slower than normal biotransformation rate leads to increased anesthetic blood levels and potentially increases toxicity.
Hypotension
Congestive heart failure (CHF)
Poor liver function
Cirrhosis

Front 9

Where does excretion of LA occur in the body?

Back 9

The kidneys are the primary excretory organ for both the local anesthetics and its metabolites. A percentage of a given dose of local anesthetic drug will be excreted unchanged in the urine.

Front 10

What 2 systems in the body are most susceptible to the action of LAs?

Back 10

CNS and CVS. Most systemic reactions are related to plasma level of LA.

Front 11

Describe the 4 phases of the action of LA on the CNS

Back 11

Anticonvulsant properties: raise the seizure threshold. Doses of 2-3 mg/kg given at a rate of 40 to 50 mg/min (0.5-4 µg/ml).
Preconvulsive Phase: Direct depressant action of the local anesthetic on the CNS (4.5-7µg/ml).
Slurred speech
shivering
muscular twitching
tremor in muscle of face and distal extremities


Convulsive Phase: Further elevation of the local anesthetic blood level produces clinical signs and symptoms consistent with a generalized tonic-clonic convulsive episode (>7.5 µg/ml)


Both inhibitory and facilitatory impulses are totally totally depress , producing general CNS depression

Front 12

What is the effect of LA on the CVS?

Back 12

Local anesthetic drug action decreases electrical excitability of the myocardium, decreases conduction rate, and decreases the force of contraction.

Front 13

Name 4 factors in selection of local anesthetic

Back 13

1.Length of time that pain control is required
2.Potential for discomfort in the post- treatment period
3.Requirement for hemostasis during treatment
4.Medical status of the patient

Front 14

Absolute contraindication

Back 14

Implies that under no circumstance should the drug be administered to the patient because the possibility of potentially toxic or lethal reactions is increased

Front 15

Relative contraindication

Back 15

The drug in question may be administered to the patient after carefully weighing the risk of using the drug to its potential benefit, and if an acceptable alternative drug is not available

Front 16

1. What impulses are favored in the preconsulvatory stage and the convulsive stage, and final stage?

Back 16

1. preconsulive stage - inhibitory stage is more profoundly depressed than facilitatory

2. final stage - both inhibitory and facilitatory are depressed producing generalize CNS depression
2. convulsive - inhibitory impsulve totally depressed, unopposed facilitatory impulse