<prompt> A 12 yr old child presents with fever and cervical lymphadenopathy for last 36 hours. Oral examination shows a grey membrane on the right tonsil. What is the primary treatment?Penicillin IV for 10 days20000 -40000 units IM equine derived antitoxin80,000-1,20,000units IM equine derived antitoxinErythromycin to be given for 2 weeks  <response>: The primary treatment is 20000 -40000 units IM equine derived antitoxin. Above mentioned clinical signs and symptoms gives a presumptive diagnosis of Diphtheria. Treatment of diphtheria: - Equine derived Antitoxin-which neutralizes the circulating diphtheria toxin. - Moderate cases with 3 days pharyngeal or laryngeal: 20000 -40000 units IM. - Serious cases with 3days disease: 80,000 -1,20,000 units IV and IM combined. - Penicillin Or Erythromycin to be given for 2 weeks for eradication of bacterium from throat Isolation of the patient for 48 hrs. 