Pyrexia

 

🔥 PYREXIA (FEVER) —

 

1. INTRODUCTION

• Pyrexia (Greek: pyretos = fire)
• Pyrogens = substances that induce fever

Types of Pyrogens:

1. Exogenous (external):

• Microbial products
• Lipopolysaccharide (Gram-negative bacteria)
• Toxins from Gram-positive bacteria (e.g., Staphylococcus aureus)

2. Endogenous (internal):

• Cytokines produced by immune cells
• IL-1, IL-6, TNF-α

2. DEFINITION

• Fever = regulated rise in body temperature due to increase in hypothalamic set point
• Normal: 36.5–37.5°C

3. TEMPERATURE MEASUREMENT

• Oral
• Axillary
• Rectal (most accurate in children)
• Tympanic membrane

4. TYPES OF FEVER

Type	Feature	Examples
Continuous	Persistent, minimal fluctuation	Typhoid, pneumonia
Intermittent	Fever + normal temperature phases	Malaria
Remittent	Fluctuates but never normal	Infective endocarditis
Relapsing	Fever returns after normal period	Borrelia infections

5. SIGNS & SYMPTOMS

• Shivering (rigors)
• Anorexia
• Dehydration
• Lethargy
• Headache
• Poor concentration
• Sleepiness

Severe cases:

• Irritability
• Confusion
• Delirium
• Convulsions (children)

6. DRUG-INDUCED FEVER

Class	Examples
Antimicrobials	Isoniazid
Antiarrhythmics	Procainamide, Quinidine
Antiepileptics	Phenytoin, Carbamazepine
Antihypertensives	Methyldopa
Antifungals	Amphotericin B
Others	Interferons, Sulfonamides

⚠️ Note:

• Cocaine/ephedrine → hyperthermia, not true fever

7. PATHOPHYSIOLOGY

Mechanism:

1. Infection → release of exogenous pyrogens
2. Activation of immune cells
3. Release of cytokines (IL-1, IL-6, TNF-α)
4. Stimulate hypothalamus → ↑ Prostaglandin E2 (PGE2)
5. Set point increases

Body response:

• Vasoconstriction → ↓ heat loss
• Shivering → ↑ heat production

👉 Result: Fever develops

8. FEVER vs HYPERTHERMIA (VERY IMPORTANT)

Feature	Fever	Hyperthermia
Set point	Increased	Normal
Cause	Pyrogens	Heat/drugs
Control	Regulated	Unregulated
Paracetamol effect	Works	No effect

9. MANAGEMENT

A. Non-Pharmacological

• Adequate hydration (ORS, fluids)
• Rest
• Light clothing
• Lukewarm sponging

❌ Avoid:

• Ice baths
• Alcohol rubs (increase shivering → worsen fever)

B. During Fever Care

• Maintain room temperature (not too hot/cold)
• Use fan if needed
• Remove excess clothing
• Lukewarm bath helps

C. Home Remedies (Supportive Only)

• Bed rest
• Fluids (herbal teas, lemon grass tea)
• Turmeric milk (symptomatic relief only)

⚠️ Note:

• No strong scientific evidence → not primary treatment

10. PHARMACOLOGICAL MANAGEMENT

Drug of Choice: Paracetamol

Adults:

• 500–650 mg every 6–8 hours
• Max: 3–4 g/day

Children:

• 10–15 mg/kg/dose every 6 hours

⚠️ Correction:

• Always use weight-based dosing in children

11. PREVENTION

• Hand hygiene
• Safe food and water
• Infection control
• Isolation of infected individuals

12. ROLE OF PHARMACIST

• Provide correct dose of paracetamol
• Assess severity of fever
• Advise hydration & rest
• Refer to doctor if:
• Fever persists >2–3 days
• Very high fever
• Associated severe symptoms

⚠️ Caution:

• Avoid overdose of paracetamol → hepatotoxicity
• Extra caution in alcoholics

13. CASE STUDY (EXAM FORMAT)

Case:

• Patient with fever (101°F)

Management:

1. Confirm temperature
2. Give Paracetamol 650 mg
3. Advise:
• Bed rest
• Fluids
4. Monitor symptoms
5. Refer if not improved

🔑 QUICK REVISION (LAST MINUTE)

• Fever = ↑ hypothalamic set point
• Key mediator = PGE2
• Cytokines = IL-1, IL-6, TNF-α
• DOC = Paracetamol
• Avoid ice/alcohol rub
• Fever ≠ Hyperthermia