Certainly. Based on the information provided—including the clinical input of "sinus"—the most likely diagnosis is **acute sinusitis** (rhinosinusitis) as the cause of headache in this 13-year-old male. Below is a comprehensive, evidence-based treatment plan:

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### 1. Primary Diagnosis

**Acute Sinusitis (Acute Rhinosinusitis)**

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### 2. Treatment Goals

- Relieve headache and sinus symptoms
- Eradicate infection (if bacterial)
- Prevent complications (e.g., orbital or intracranial spread)
- Restore normal sinus function
- Minimize unnecessary antibiotic use

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### 3. Medication Recommendations

#### a. **First-line: Symptomatic Management**
- **Analgesics/Antipyretics:**  
  - *Acetaminophen* 10–15 mg/kg/dose every 4–6 hours as needed (max 75 mg/kg/day)
  - *Ibuprofen* 5–10 mg/kg/dose every 6–8 hours as needed (max 40 mg/kg/day)

- **Nasal Saline Irrigation:**  
  - Isotonic saline nasal spray or irrigation 2–3 times daily

- **Intranasal Corticosteroids** (if significant nasal congestion or allergic rhinitis):  
  - *Fluticasone nasal spray* 1–2 sprays per nostril once daily

#### b. **Antibiotics**  
*Indicated only if:*
- Symptoms persist >10 days without improvement
- Severe symptoms (fever ≥39°C, purulent nasal discharge, facial pain) for ≥3 consecutive days
- Worsening symptoms after initial improvement ("double sickening")

**First-line antibiotic:**
- *Amoxicillin-clavulanate* 45 mg/kg/day (amoxicillin component) divided every 12 hours for 10 days  
  - If non-severe penicillin allergy: *Cefdinir* 14 mg/kg/day in 1–2 doses for 10 days  
  - If severe allergy: *Levofloxacin* 10–20 mg/kg/day once daily for 10 days

**Note:** Do not use macrolides due to resistance.

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### 4. Non-Pharmacological Interventions

- Encourage adequate hydration
- Warm compresses over sinuses for pain relief
- Rest
- Avoid exposure to irritants (smoke, strong odors)
- Humidified air (cool mist humidifier in bedroom)

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### 5. Follow-up Schedule

- **Routine:** Reassess in 48–72 hours if symptoms worsen or fail to improve
- **Earlier:** Immediate evaluation if red flag symptoms develop (see below)
- **After antibiotics:** Re-evaluate at end of course if not fully resolved

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### 6. Monitoring Parameters

- Symptom resolution (headache, nasal congestion, discharge, facial pain)
- Temperature (fever resolution)
- Adverse effects of medications (GI upset, rash, allergic reaction)
- Signs of complications (see below)

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### 7. Patient Education Points

- Most sinus infections are viral and resolve without antibiotics
- Use antibiotics only as prescribed; complete the full course if started
- Proper technique for nasal saline irrigation
- Recognize and report red flag symptoms promptly
- Avoid overuse of decongestants (risk of rebound congestion)
- Maintain good hand hygiene to prevent spread of infection

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### 8. Potential Complications to Watch For

- **Orbital complications:** Periorbital swelling, erythema, visual changes, ophthalmoplegia
- **Intracranial complications:** Severe headache, altered mental status, persistent vomiting, neck stiffness, seizures
- **Chronic sinusitis:** Symptoms >12 weeks
- **Antibiotic adverse reactions:** Rash, diarrhea, anaphylaxis

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**Summary:**  
Mr Patient likely has acute sinusitis. Begin with symptomatic management; reserve antibiotics for persistent, severe, or worsening symptoms. Educate on red flags and ensure close follow-up. Consult ENT or refer to hospital if complications or red flags arise.

**Always recommend consultation with a healthcare professional for confirmation of diagnosis and ongoing management.**