How many days should dexamethasone be injected into a rat? - briefly
In typical rodent experiments dexamethasone is given daily for 5–7 days to produce acute glucocorticoid effects, whereas chronic studies extend the injection schedule to 14 days or longer.
How many days should dexamethasone be injected into a rat? - in detail
The length of dexamethasone administration in rodents depends on the experimental goal, dose, route, and animal characteristics.
For short‑term anti‑inflammatory or immunosuppressive experiments, researchers commonly inject the drug once daily for 1–5 days. This period is sufficient to achieve peak glucocorticoid effects without inducing marked adrenal suppression.
Chronic disease models, such as arthritis, lung fibrosis, or stress‑induced depression, often require prolonged exposure. Protocols typically extend from 7 days to 28 days, with daily injections or alternate‑day schedules. Longer regimens (>4 weeks) increase the risk of weight loss, hyperglycemia, and bone demineralization; therefore, monitoring of physiological parameters and implementation of humane endpoints are mandatory.
Key factors influencing the chosen schedule:
- Dose intensity: High doses (≥1 mg kg⁻¹) accelerate onset of systemic side effects, favoring shorter courses. Low doses (≤0.1 mg kg⁻¹) allow extended administration.
- Study objective: Acute cytokine suppression needs only a few days; remodeling or gene‑expression changes generally require at least one week.
- Animal strain and age: Young, fast‑metabolizing strains (e.g., Sprague‑Dawley) may clear the drug more rapidly, permitting longer dosing intervals.
- Route of delivery: Intraperitoneal injection yields faster absorption than subcutaneous implantation of slow‑release pellets, which can sustain drug levels for 2–4 weeks.
- Ethical considerations: Institutional guidelines often cap continuous glucocorticoid exposure at 28 days unless justified by a rigorous scientific rationale and accompanied by enhanced welfare monitoring.
Typical schedules reported in peer‑reviewed literature:
- 0.5 mg kg⁻¹ i.p., once daily, 3 days – acute inflammation model.
- 0.2 mg kg⁻¹ i.p., every other day, 14 days – arthritis induction.
- 0.05 mg kg⁻¹ subcutaneously via osmotic pump, continuous release for 21 days – chronic stress study.
When planning an experiment, align the injection duration with the mechanistic endpoint, verify that the chosen period does not exceed species‑specific tolerance, and document all monitoring procedures.