What is the recommended dose of azithromycin for a 64-year-old female weighing 106 pounds with normal renal function?

Azithromycin Dosing for a 64-Year-Old Female Weighing 106 Pounds with Normal Renal Function

For a 64-year-old female weighing 106 pounds (48 kg) with normal renal function, the recommended dose of azithromycin is 500 mg on day 1, followed by 250 mg once daily on days 2 through 5.

Dosing Rationale

The FDA-approved standard adult dosing regimen for azithromycin applies to this patient, as:

• The patient has normal renal function, so no dose adjustment is required 1
• Her weight of 106 pounds (48 kg) is within the normal adult range
• At 64 years old, no age-specific dose adjustment is needed 1

Specific Dosing Regimens Based on Indication

The dosing regimen may vary depending on the specific indication:

Standard 5-Day Regimen (Most Common)

• Day 1: 500 mg as a single dose
• Days 2-5: 250 mg once daily 2, 1

3-Day Regimen (For Certain Respiratory Infections)

• 500 mg once daily for 3 days 1

Single-Dose Regimens (For Specific Infections)

• Genital ulcer disease/non-gonococcal urethritis: One single 1-gram dose 1
• Gonococcal urethritis/cervicitis: One single 2-gram dose 1

Administration Considerations

• Azithromycin tablets can be taken with or without food 1
• The patient should be cautioned not to take azithromycin with aluminum or magnesium-containing antacids simultaneously, as these reduce absorption 2
• The medication should be taken at least 2 hours before or after antacids 2

Monitoring and Precautions

• Common side effects include gastrointestinal disturbances (abdominal discomfort, diarrhea, nausea, vomiting), headache, and dizziness 2
• Monitor for potential drug interactions, particularly with medications metabolized by the cytochrome P450 enzyme system (e.g., digoxin, triazolam, ergot alkaloids) 2
• No specific monitoring of drug levels is required, unlike with aminoglycosides or vancomycin 3

Special Considerations

• Despite the patient's age (64 years), no dose adjustment is needed based on age alone 1
• With normal renal function, no renal dose adjustment is required 1
• The pharmacokinetics of azithromycin allow for once-daily dosing due to its extensive tissue distribution and long half-life 4, 5
• The drug achieves high tissue concentrations that exceed serum concentrations by up to 100-fold following a single 500 mg dose 4

This dosing recommendation follows the standard adult dosing guidelines for azithromycin as established by the CDC and FDA, which are appropriate for this 64-year-old female patient with normal renal function.