pharmacology of analgesics

1. Drugs Used to treat pain and
Inflammation
Dr. Haji Bahadar, Assistant Professor
KMU-IPMS

2. What is pain?
• Pain is an unpleasant sensation.
Classification:
1.Acute Pain: Acute pain typically comes on
suddenly and has a limited duration. It's
frequently caused by damage to tissue such as
bone, muscle, or organs.
2. Chronic Pain: Chronic pain lasts longer than
acute pain. It's usually associated with a long-
term illness, such as osteoarthritis.

3. 2.1. Neuropathic: pain initiated or caused by a
primary lesion or disease in the
somatosensory nervous system.
2.2. Inflammatory: pain resulted due to
activation and sensitization of the nociceptive
pain pathway by a variety of mediators
released at a site of tissue inflammation.
(appendicitis, rheumatoid arthritis)

4. Pain Receptors
• Pain receptors are also called nociceptors.
means sensitive to noxious stimuli. Noxious
stimuli are stimuli that elicit tissue damage
and activate nociceptors.
• Nociceptors are receptors that detect signals
from damaged tissue. Nociceptors are free
(bare) nerve endings found in the skin,
muscle, joints, bone and viscera.

7. Double pain sensation
• Two separate pain sensations in short time
intervals. Fast pain sensation is carried via A
delta fibers and is followed several seconds
later with slow transmitting pain information
carried via C fibers

8. What is inflammation?
Inflammation is the body's response to injury.
Inflammation is body's immune response.
Physical: Burns, Frostbite, Physical injury
Biological: Infection by pathogens
Chemical: toxin or toxicant
Types: Acute and chronic

9. Signs of inflammation
• Pain - the inflamed area is likely to be painful
.Chemicals that stimulate nerve endings are
released, making the area much more sensitive.
• Redness - this is because the capillaries are filled
up with more blood than usual.
• Immobility - there may be some loss of function.
• Swelling - caused by an accumulation of fluid.
• Heat - more blood in the affected area makes it feel
hot to the touch.

10. Rheumatoid arthritis

11. Chemicals involved
• Cytokines
• Histamine
• Prostaglandins (pain nerve endings
sensitizing)

13. Nonsteroidal anti-inflammatory drugs
(NSAIDs) TRADE NAMES (DRUG MANNUAL)
Non selective COX
inhibitors
• Aspirin
• Diclofenac
• Indomethacin
• Ketorolac
• Meloxicam
• Piroxicam
• Fenoprofen
• Flurbiprofen
• Ibuprofen
• Ketoprofen
• Naproxen
• Paracetamol
(no anti inflammatory)
COX-2 inhibitors
Selective COX-2 inhibitors are a type of non-steroidal
anti-inflammatory drug (NSAID) that directly targets
cyclooxygenase-2, COX-2, an enzyme responsible
for inflammation and pain. Targeting selectivity for
COX-2 reduces the risk of peptic ulceration. Drugs are
celecoxib, rofecoxib
Selective

14. Steroidal anti inflammatory drugs
• Steroid is an organic compound with four rings.
• The steroid core structure is composed of
seventeen carbon atoms, bonded in four "fused"
rings.

15. Difference between non steroid and
steroid structures
Aspirin Dexamethasone

17. Mechanism of action
During inflammation prostaglandins stimulate peripheral
nerve endings producing pain impulses that are carried to
the CNS. NSAIDs relieve pain by selectively inhibiting
prostaglandin synthesis.

18. Indications
• Muscle aches and pain
• Toothache
• Dysmenorrhea
• Joint Pain (osteoarthritis)
• Inflammation
• Rheumatoid arthritis
• Removal of acne(salicylic acid)
Salicylic acid 6 % topical gel

19. Side effects
• Nausea due to erosion of stomach lining
• Decrease cytoprotective mucus secretion.

20. Side effects
• Vomiting
• Peptic ulcer disease
• Gastrointestinal bleeding
• Prolong bleeding time (Aspirin)
• Hepatoxicity (elevated serum enzymes like
alkaline phosphatase, serum glutamic-pyruvic
transaminase SGPT or ALT)(Paracetamol)
• Hypersensitivity (in sensitive patients)- rash,
laryngeal edema, asthma (Aspirin)
• Kidney damage(analgesic nephropathy)

21. Contraindications
• Severe hepatic diseases (Aspirin, diclofenac,
paracetamol)
• Vitamin K deficiency (Aspirin)
• Hemophilia (bleeding disorder) (Aspirin)
• Children (Aspirin) causing Reye
syndrome(self)
• Patients receiving anticoagulants such as
coumarin and heparin (aspirin)
• Asthma (aspirin)

22. Analgesics and pain relief in pregnancy and breastfeeding
• Paracetamol
• Mefanamic acid