Sinusitis, an inflammation of the tissue lining the sinuses and nasal passages, is a common condition that causes facial pain, pressure, and congestion. While many cases are viral and resolve on their own, a small number are caused by bacteria. Amoxicillin, a penicillin-class antibiotic, is frequently prescribed when a bacterial infection is suspected. This article discusses the context for using this antibiotic, typical dosage, potential side effects, and next steps if treatment fails.
Identifying Bacterial Sinusitis
Most acute sinusitis cases are viral, meaning that antibiotics like Amoxicillin are ineffective. A bacterial infection is suspected only when symptoms follow a specific pattern or exceed a certain duration. Doctors typically use clinical criteria to differentiate between viral and bacterial sinusitis before prescribing an antibiotic.
A diagnosis of acute bacterial sinusitis is typically made when one of the following patterns is observed:
- Persistent illness, where symptoms last ten days or longer without improvement.
- A “double sickening” course, involving initial improvement followed by a sudden worsening of symptoms (e.g., increased nasal discharge, cough, or fever).
- Severe onset, characterized by a high fever of 102.2°F (39°C) or more, accompanied by thick, discolored nasal discharge for at least three consecutive days.
Standard Dosage and Treatment Duration
The Amoxicillin dosage is determined by the patient’s age, weight, and infection severity. Adult formulations are typically 500 mg or 875 mg tablets. For mild to moderate infections, a typical adult dose is 500 mg every twelve hours; more severe infections may require 875 mg every twelve hours.
In pediatric cases, the dosage is calculated based on the child’s weight, often ranging from 45 to 90 mg/kg of body weight per day, divided into two or three doses. The duration of treatment for uncomplicated adult cases is commonly five to seven days. Patients must complete the entire course as prescribed, even if symptoms improve quickly, to prevent infection resurgence and antibiotic resistance.
Common Side Effects and Safety Warnings
Amoxicillin can cause side effects, most of which are mild and related to the digestive system. Common issues include nausea, vomiting, stomach upset, and diarrhea. Taking the medication with food can sometimes help reduce these gastrointestinal symptoms.
More serious, though rare, side effects require immediate medical attention, such as signs of a severe allergic reaction:
- Hives or a widespread rash.
- Swelling of the face, throat, or tongue.
- Difficulty breathing.
Another serious concern is antibiotic-associated diarrhea, which signals an overgrowth of the bacterium Clostridioides difficile (C. diff) in the gut. This diarrhea can be watery or bloody and may occur months after the course is finished, requiring prompt consultation.
Next Steps If Amoxicillin Does Not Work
If symptoms do not improve within three to seven days of starting Amoxicillin, the treatment has likely failed. This lack of response may indicate the infection was viral or that the bacteria are resistant to Amoxicillin. Patients should contact their healthcare provider to discuss a change in treatment.
The most common next step is switching to a second-line antibiotic, often Amoxicillin-Clavulanate (Augmentin). The clavulanate potassium helps Amoxicillin overcome bacterial resistance mechanisms. Alternative options for treatment failure or penicillin allergy include certain cephalosporins or respiratory fluoroquinolones. If the infection is severe or the response to second-line therapy is poor, the provider may consider referral to a specialist.