pharmacotherapeutics analgesics

Question 1

what is pain

Answer 1

an unpleasant sensory and emotional experience associated with actual or potential tissue damage

Question 2

pain classification

Answer 2

somatic, visceral or neuropathic
acute vs chronic

Question 3

why is pain important

Answer 3

protective function, alerts about a problem in the body
protects against against further injury e.g. generation of withdrawal reflexes
aids healing, forces the body to stay at rest

Question 4

why do we treat/control pain

Answer 4

decreases the negative impact on the body
decreases the systemic complication associated with pain
decreases the likelihood of chronic pain development
improves outcomes of treatment
increase patient satisfaction
increases productivity and improves quality of life

Question 5

methods to relieve pain

Answer 5

remove peripheral stimulus
interrupt the nociceptive input
stimulate nociceptor inhibitory mechanisms
modulate central appreciation of pain
block or remove secondary factors maintaining pain

Question 6

pain pathways

Answer 6

first order neuron (cell body in the dorsal root ganglion or trigeminal brainstem nuclear complex) transmit pain stimulus from a peripheral receptor (nerve endings = nociceptor)
second order neuron in the dorsal root of the spinal chord, axon crosses the midline to ascend in the spinothalamic tracts to the thalamus
Third order neuron projects to the higher brain centres including the somatosensory cortex and the limbic system

Question 7

pain processing

Answer 7

transduction
transmission
modulation
perception

Question 8

dental pain pathways

Answer 8

Sensory supply to the teeth and oral mucosa
Afferent fibres, both myelinated and unmyelinated,(C fibres – dull aching and A-& fibres – sharp shooting) in the trigeminal nerve enter the brainstem to the trigeminal nucleus complex.
This complex comprises four nuclei, the motor nucleus and three sensory nuclei
Information from all over the body converges on the medial reticular formation and is transmitted to thalamic nucleus
The reticular system acts as a centre controlling what information is passed on and what is rejected
The descending inhibitory pathways can also affect the transmission and sensation of pain.

Question 9

inflammation

Answer 9

A complex biological response of the body tissues to harmful stimuli and is a protective response involving immune cells, blood vessels and molecular mediators.
The function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells, tissues damaged from the original insult and the inflammatory process, and initiate repair.

Question 10

classic signs of inflammation

Answer 10

heat, redness, swelling, pain, loss of function

Question 11

peripheral and central mediators of pain

Answer 11

Tissue damage —- chemical substances released from the damaged tissues (e.g. bradykinins, histamine, Eicosanoids)——– act on nociceptors to transmit nociceptive information from the primary afferent neurone.
This transmission is carried on in the secondary ,tertiary and higher order neurones with the aid of chemical transmitters called neurotransmitters.

Question 12

what are the neurotransmitter involved

Answer 12

The Eicosanoids, 4 main groups !the prostaglandins especially the E series, prostacyclin’s, thromboxane A2 and the leukotrienes.
The prostaglandins are the prime candidates as mediators of pain associated with inflammation

Question 13

cyclooxyrgenase

Answer 13

Cyclooxygenase is important for production of prostaglandins
Analgesics function by blocking the cyclooxygenase dependant production of prostaglandins.
The management of pain is directed at altering the peripheral and central mechanisms responsible for the propagation of pain impulses

Question 14

classes of analgesics

Answer 14

Aspirin= Acetylsalicylic acid
Non Steroidal Anti inflammatory drugs (NSAIDS)
Paracetamol = Acetaminophen
Opioids and Opiates
Combinations

Question 15

aspirin (weak organic acid)

Answer 15

Inhibits the synthesis of the important chemical mediators: the eicosanoids
Irreversibly inhibits the cyclooxygenase enzyme system (cox- 1 and cox-2)

Question 16

pharmacologic properties of aspirin

Answer 16

_Anti inflammatory _Analgesic, mild to moderate _Have central antipyretic activity by inhibiting prostaglandin production in the hypothalamus _ Antithrombotic

Question 17

how is aspirin taken

Answer 17

taken orally, new intravenous preparations

Question 18

pharmacokinetics of aspirin

Answer 18

Rapid GIT absorption partly from the stomach, but mainly from the upper small intestines
_Half life of 20-30 min
_Metabolised in the liver
_Excreted in urine

Question 19

unwanted effects of aspirin

Answer 19

vary between individuals, related to dosage and chronic usage
GIT
uricosuric effects
effects in kidney
tinnitus
haemostat effects
aspirin hypersensitivity
drug interactions

Question 20

aspirin overdose

Answer 20

10-30g stat can be fatal
increased carbon dioxide production in skeletal muscle due to deranges metabolism
respiratory depression
metabolic acidosis
impaired renal function
hyperthermia and dehydration
death

Question 21

Reye’s syndrome

Answer 21

Occurs in childhood, it involves an acute encephalopathic illness and fatty degeneration of the viscera especially in the liver
It arises after an acute infectious illness e.g. chicken pox or influenza.
90% of cases are associated with Aspirin use

Question 22

symptoms of Reye’s disease

Answer 22

personality changes ,vomiting, confusion, seizures

Question 23

pathogenesis of eye’s syndrome

Answer 23

The pathogenesis is not clear but is proposed to be an interaction between aspirin and viral infection that leads to cell mitochondria damage, in genetically susceptible individuals.

Question 24

application in dentistry of aspirin

Answer 24

Widely used for post operative dental pain
Efficacy is dose related
Short duration, therefore unwanted effects are minimal
Given post surgery, there is little risk of haemorrhage
Packed in the sulcus, it causes severe sloughing and ulceration of the buccal mucosa and is of no value for pain relief.
Beware of drug interactions e.g. anticoagulants

Question 25

NSAIDS pharmacological effect

Answer 25

Have Aspirin's pharmacological properties Anti inflammatory and analgesic effect because they inhibit the synthesis of the eicosanoids COX-1 and COX-2 NSAIDS

Question 26

use mainly for the treatment of which issues

Answer 26

rheumatic arthritis and other music-skeletal disorders

Question 27

most widely used NSAID

Answer 27

ibuprofen - most popular in dentistry

Question 28

paracetamol pharmacological effects

Answer 28

Has both the analgesic and antipyretic properties similar to those of aspirin ,however has little or no anti inflammatory action, for which there is no satisfactory explanation. inhibits brain prostaglandin synthase

Question 29

pharmacokinetics of paracetamol

Answer 29

Well absorbed from the small intestines after oral ingestion Half life is 2hrs, peak plasma concentration after 30-60 min Metabolised in the liver and excreted in urine

Question 30

how is paracetamol taken

Answer 30

intravenous and suppository preparation available

Question 31

unwanted effects and overdose of paracetamol

Answer 31

Fewer side effects than other analgesics at normal therapeutic doses, therefore the safest analgesic Skin rashes, WBC disorders have been reported Overdose----hepatotoxicity which is the most serious complication A single dose of 10-15g-----liver damage, 25g----death. With symptoms only 2-6 days later

Question 32

uses of paracetamol in dentistry

Answer 32

useful where aspirin is controlled-indicated some elixirs contain high concentration of sugar, therefore can be cariogenic efficacy as a post operative analgesic has been scientifically proven

Question 33

morphine

Answer 33

most widely used of the opiates and considered to be the most potent

Question 34

pethidine

Answer 34

for severe to moderate pain

Question 35

codeine

Answer 35

for moderate to mild pain

Question 36

opiods and opiates (narcotics)

Answer 36

Referred to as centrally acting analgesics and loosely as narcotics Receptors are found all throughout the CNC with high concentrations in the limbic system, substancia gelatinosa, the spinal nucleus of trigeminal nucleus and the thalamus Their analgesic effect is generated mainly by the inhibition of nociceptive impulses in the CNS, they also activate descending inhibitory pathways. At cellular level binding of opioids receptor may lead to decreased presynaptic neurotransmitter release, hyperpolarisation of postsynaptic neurons and inhibition of impulse propagation.

Question 37

morphine pharmacokinetics

Answer 37

metabolised in the liver excreted via the kidney, with half life of 3 hours given orally, but parenterally for optimal use

Question 38

pharmacodynamics and pharmacological properties

Answer 38

Analgesia Effective against psychological and emotional components of pain Other central effects like drowsiness, sedation, euphoria all of which add to the general comfort of a patient in pain Do not alter the sensations e.g. touch, pressure, vision or hearing Effective against dull continuous pain 10mg morphine gives pain relief within 30min for 4-5hrs GIT—treat diarrhoea, dysentery and produces a degree of constipation suppresses cough has cardiovascular effects on BP, cardiac output and heart rate

Question 39

unwanted effects of morphine

Answer 39

respiratory depression dependence nausea and vomitting constriction of the pupils decreases urinary flow overdose - death from respiratory depression snd low BP

Question 40

uses of morphine in dentistry

Answer 40

Limited-----Dental pain can be treated effectively locally Surgical pain is mostly due to inflammation and opioids have no anti inflammatory component Combination analgesia can be used only when single treatments have failed.

Question 41

multimodal therapy/combination analgesia

Answer 41

Synchronous administration of two or more pharmacological agents or approaches, each with a distinct mechanism of action to alleviate pain. Step-wise approach for the introduction of analgesics, aimed at avoiding over medication, reducing the side effects, therefore keeping the therapeutic schedule as simple as possible. Aim to eliminate suffering from the patients life. Tailor therapy for the patients condition.

Question 42

other therapeutic methods

Answer 42

anti-depressants anti convulsants corticosteroids nitric oxide local anaesthesia