Simeprevir Pharmacology

Here, we take a few minutes to learn more about simeprevir pharmacology; an important drug used in the treatment of viral infections. Here, we learn more about what the medicine is used for, how the medicine works as well as what prominent side effects and drug interactions it has. We also learn about the clinical implications of simeprevir use.

Let’s take a few minutes to review the fundamental facts you need to know.

Indications

Simprevir is an antiviral medicine used to treat hepatitis C – genotypes 1 and 4.

It is not used alone. Instead, simeprevir is used alongside other antiviral drugs, such as sofosbuvir, ribavirin and peginterferon. When used in this combined format, it delivers a cure rate of greater than 95 percent. The medicine is usually taken once daily for up to 3 months.

Simeprevir was introduced to the market in 2013. Given the clinical success of simeprevir, it has since been placed on the WHO List of Essential Medicines.

Brand names: Olysio

Mechanism of action

At the most fundamental level, simeprevir operates as a protease inhibitor of the hepatitis virus.

The drug is only used to treat genotypes 1 and 4. Genotype 1 is by far the most common cause of hepatitis C, accounting for just under half of all hepatitis cases.

More specifically, simeprevir inhibits NS3/4A protease. This inhibits viral protein synthesis and, by extension, viral cell maturation.

Side effects

Side effects with simeprevir include:

  • Photosensitivity
  • Rash
  • Headache
  • Fatigue
  • Itch

Other effects include GI effects (nausea etc.), muscle pain and aches, elevated liver enzymes, difficulty sleeping and, rarely, difficulty breathing.

Clinical considerations

Clinical considerations of simeprevir pharmacology include:

  • Simeprevir should be taken with food to enhance bioavailability.
  • Simeprevir may reactivate latent hepatitis B in patients previously exposed. This carries a dangerous risk of potentially fatal liver problems.
  • The three most common side effects – affecting 1-in-4 patients taking the drug – are photosensitivity, rash and severe itch.
  • Simeprevir is primarily metabolized by CYP3A4. Drugs that enhance / inhibit this enzyme, then, impact the therapeutic effects of simeprevir. Inducers, such as rifampicin, decrease simeprevir plasma concentration whereas CYP3A4 inhibitors, such as ritonavir, increase plasma concentrations.
  • Simeprevir is avoided in pregnancy because it is typically taken alongside teratogenic antiviral drugs – such as ribavirin or peginterferon-alfa.
  • Avoid simeprevir in cases of significant liver impairment or end-stage renal disease.

Simeprevir remains an important medicine in the clinical cabinet of hepatitis C. The drug, when used alongside other hepatitis C medicines, demonstrates a remarkably high cure rate. However, the drug comes with significant clinical risks, not least the potential hepatic damage that hepatitis B reactivation can cause.

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