From the Guidelines
Lethargy is a potential side effect of acyclovir, particularly in patients with impaired renal function or those receiving high doses, and patients experiencing this symptom should consult their healthcare provider without interrupting the treatment. The management of herpes simplex encephalitis with acyclovir, as outlined in the clinical practice guidelines by the Infectious Diseases Society of America 1, emphasizes the importance of prompt initiation of therapy to reduce morbidity and mortality. While the guidelines primarily focus on the treatment of herpes simplex encephalitis, they also highlight the potential for adverse outcomes, including neurological side effects, when using acyclovir. Some key points to consider when managing acyclovir-related lethargy include:
- The dosage of acyclovir for patients with normal renal function is 10 mg/kg intravenously every 8 h for 14–21 days, as recommended by the guidelines 1.
- Higher doses, such as 20 mg/kg intravenously every 8 h for 21 days, have been used in neonates with herpes simplex encephalitis, resulting in decreased mortality 1.
- Patients experiencing lethargy or other neurological side effects, such as confusion, hallucinations, or tremors, should seek medical attention promptly to determine the best course of action, which may include adjusting the dosage or considering alternative antiviral medications.
- Staying well-hydrated while taking acyclovir may help reduce the risk of lethargy and other side effects, particularly in patients with impaired kidney function. It is essential to weigh the benefits of acyclovir treatment against the potential risks of side effects like lethargy, considering the significant reduction in morbidity and mortality associated with prompt and appropriate treatment of herpes simplex encephalitis, as demonstrated in the guidelines 1.
From the FDA Drug Label
Adverse events that have been reported in association with overdosage include agitation, coma, seizures, and lethargy. Treatment with Acyclovir Tablets did not affect varicella-zoster virus-specific humoral or cellular immune responses at 1 month or 1 year following treatment. decreased the proportion of patients with fever, anorexia, and lethargy by day 2
- Lethargy is a potential side effect of Acyclovir overdose, as reported in the drug label 2.
- Acyclovir treatment can decrease the proportion of patients with lethargy in the context of chickenpox treatment, as shown in clinical trials 2.
From the Research
Acyclovir Lethargy
- Acyclovir is a widely used antiviral medication that can cause serious side effects, including lethargy, in certain patients 3.
- The medication is commonly used to treat herpes virus infections, particularly herpes simplex virus and varicella-zoster virus.
- Lethargy is a potential side effect of acyclovir, especially in patients with renal impairment or those who receive inappropriate dosing 4, 5.
- A case report published in 2011 described a 65-year-old man with chronic kidney disease who developed progressive confusion and ataxia after starting acyclovir, which resolved after prompt dialysis 3.
- Another study published in 2021 reported two cases of patients developing neurotoxic side effects, including lethargy, while being treated with acyclovir for herpes zoster 5.
- The study highlighted the importance of monitoring patients with impaired renal function or multiple comorbidities for potential neurotoxic side effects during acyclovir therapy.
- Acyclovir must be renally dosed and carefully monitored through drug level measurement in patients with limited kidney function to prevent serious side effects, such as lethargy 3.