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Aciclovir-induced neurotoxicity
  1. Frederick William Vonberg1,2,
  2. Angelo Dawson1,
  3. Gregory Scott1,3,
  4. Nicholas Davies1,2
  1. 1 Department of Neurology, Imperial College Healthcare NHS Trust, London, UK
  2. 2 Department of Neurology, Chelsea and Westminster Healthcare NHS Trust, London, UK
  3. 3 Imperial College London, London, UK
  1. Correspondence to Dr Frederick William Vonberg, Department of Neurology, Imperial College Healthcare NHS Trust, London, W2 1NY, UK; frederick.vonberg{at}


Aciclovir-induced neurotoxicity results from the accumulation of aciclovir and its metabolite 9-carboxymethoxymethylguanine (CMMG). It occurs predominantly in older patients with impaired renal function and is characterised by a combination of confusion and psychiatric changes. Seizures, myoclonus and dysarthria may also occur. Critically, peritoneal dialysis has little effect on reversing the toxic effects of aciclovir. We describe a woman in her 70s with renal failure who developed confusion and seizures after receiving aciclovir. She was ultimately diagnosed with aciclovir-induced neurotoxicity, confirmed by an elevated serum CMMG concentration. This condition is likely to be underdiagnosed and the neurologist’s primary challenge is differentiating aciclovir-induced neurotoxicity from viral encephalitis.


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  • Contributors Article conceived, prepared and written by FWV, review and edits made by AD, GS, and ND. Supervision provided by ND.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed by Lucy Kinton, Southampton, UK.

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