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Updated: May 10, 2026
11:17
Multiplex Therapeutic Drug Monitoring by Isotope-dilution HPLC-MS/MS of Antibiotics in Critical Illnesses
Published on: August 30, 2018
Doxycycline concentration over time after storage in a compounded veterinary preparation.
Mark G Papich1, Gigi S Davidson, Lisa A Fortier
1Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA. mark_papich@ncsu.edu
Summary
Compounded doxycycline liquid formulations for veterinary use showed acceptable concentrations for only 7 days. Beyond this period, doxycycline levels dropped significantly, indicating instability in these preparations.
Area of Science:
- Veterinary Pharmacy
- Compounding Pharmacy
- Drug Stability
Background:
- Doxycycline is a widely used antibiotic in veterinary medicine.
- Compounding liquid formulations allows for flexible dosing in animals.
- Stability of compounded doxycycline is crucial for effective treatment.
Purpose of the Study:
- To evaluate the concentration and stability of doxycycline in compounded liquid oral formulations.
- To determine the shelf-life of doxycycline compounded from hyclate tablets.
- To assess the impact of storage conditions on doxycycline concentration.
Main Methods:
- Doxycycline hyclate tablets were compounded into two liquid formulations (33.3 and 166.7 mg/mL).
- Formulations were stored at room temperature and refrigerated for 28 days.
- Doxycycline concentration was measured using high-pressure liquid chromatography at various time points.
Main Results:
- Doxycycline concentrations remained within acceptable limits (90-110% of reference) for the first 7 days.
- Concentrations decreased dramatically to below 20% by day 14 and remained low.
- Formulation quality also declined after 7 days; storage temperature had no discernible effect.
Conclusions:
- Compounded doxycycline liquid formulations are stable for a maximum of 7 days.
- Veterinary professionals should be aware of the limited shelf-life of these preparations.
- Doxycycline concentration cannot be guaranteed beyond 7 days in these compounded vehicles.
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