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What Are the Potential Drug Interactions of Simeprevir?

March/April 2014

In December 2013, Health Canada approved the sale and use of a new anti-HCV drug called simeprevir. This drug is sold under the brand name Galexos and is made by the Janssen company.

Simeprevir belongs to a class of drugs called HCV protease inhibitors. It is meant to be used as part of combination therapy with peginterferon and ribavirin. However, at least one clinical trial has found that the combination of simeprevir and sofosbuvir is potent, highly effective and safe, so some doctors may prescribe it in cases where patients have private insurance coverage that will pay for it. Until simeprevir is listed on provincial and territorial formularies, it is not clear if provinces and territories will pay for this combination.

Simeprevir is available in capsules of 150 mg and the dose is one capsule once daily. This drug does not have food or water restrictions. Simeprevir was relatively well tolerated in clinical trials and most side effects reported were of mild-to-moderate intensity. Common side effects in these clinical trials included the following:

  • rash
  • itchy skin
  • higher-than-normal levels of the waste product bilirubin in the blood
  • sensitivity to sunlight


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Drug Interactions

Drugs can influence the absorption of and the body's ability to break down other drugs. This effect of one drug on another drug(s) is called a drug interaction. Such interactions can result in intensified side effects, new side effects or the loss of effectiveness. Always speak to your nurse and doctors(s) about the medicines that you are taking, particularly your specialist(s) and family doctor. Tell them about any over-the-counter drugs you are taking, as well as any herbs or supplements. Pharmacists can be an especially helpful source of information about drug interactions.


The List of Interactions

Below is a list of actual and potential interactions that may occur with simeprevir. Please note that this list is not exhaustive. We also provide recommendations by Janssen about how to deal with some potential interactions for simeprevir users. It is important that any changes to the drugs that you are taking be made by your physician(s) to maximize your chances of recovery from HCV and minimize any risk of harm.

Here is the list of actual and potential interactions that may occur with simeprevir:

Drugs for abnormal heart rhythms

  • Digoxin: simeprevir can raise the level of digoxin in your body. Your doctor will need to monitor the amount of digoxin in your blood and perhaps adjust your dose.
  • Other drugs for abnormal heart rhythms: amiodarone, disopyramide, flecainide, lidocaine (systemic), mexiletine, propafenone, quinidine -- simeprevir can raise the level of these drugs. The manufacturer recommends that they be used cautiously and advises that their level in your blood requires monitoring.

Antiseizure drugs

  • Including carbamazepine, oxcarbazepine, phenobarbital, phenytoin -- all of these drugs can significantly reduce the amount of simeprevir in your blood. Ask your doctor for a different anti-seizure medication, as the manufacturer recommends that simeprevir should not be used with these drugs.

Antihistamines

  • Simeprevir can raise the amount of astemizole and terfenadine and Janssen recommends that they not be used.

Antibiotics -- general

  • Clarithromycin, erythromycin and telithromycin raise levels of simeprevir. Erythromycin should not be taken by patients who are prescribed simeprevir. Janssen suggests that doctors consider an alternative antibiotic, azithromycin.

Antibiotics -- TB

  • Rifampin, rifabutin and rifapentene should not be used because they significantly reduce the amount of simeprevir in the body.

Antifungal drugs

  • Itraconazole, ketoconazole, posaconazole and voriconazole all raise simeprevir levels and Janssen recommends that they not be used.

Calcium channel blockers

  • Amlodipine, bepridil, diltiazem, felodipine, nicardipine, nifedipine, nisoldipine, verapamil -- simeprevir can raise the levels of these drugs. Janssen states that they be used cautiously and that "clinical monitoring of patients is recommended."

Cholesterol medicines

  • Statins, including atorvastatin, lovastatin, pitavastatin, rosuvastatin and simvastatin -- simepevir can raise the levels of these drugs in your body. Janssen recommends starting with the lowest "necessary" dose of these medicines when taking simeprevir.

Corticosteriods (oral or intravenous)

  • Dexamethasone -- as this drug can reduce simeprevir levels, it should not be used by patients taking simeprevir.

GI drugs

  • Prepulsid, Propulsid (cisapride) -- this should not be used as it may cause abnormal heart rhythms.

Herbs

  • St John's wort (hypericin, hyperforin), milk thistle -- these herbs should not be used by people taking simeprevir, as St. John's wort can reduce the amount of simeprevir in the body and milk thistle can raise the amount of simeprevir in the body.

HIV drugs

  • Non-nukes: efavirenz (Sustiva, Stocrin and in Atripla), delavirdine (Rescriptor), etravirine (Intelence and in Complera) and nevirapine (Viramune) -- these drugs should not be used by patients who take simeprevir, as they can lower the concentration of simeprevir or vice versa.
  • Protease inhibitors: including atazanavir, cobicistat (in Stribild), darunavir, fosamprenavir, indinavir, lopinavir (Kaletra), ritonavir (Norvir and in Kaletra), saquinavir, tipranavir -- these drugs can have significant interactions with simeprevir. They can raise simeprevir levels and vice versa. Janssen recommends that people taking simeprevir do not take these protease inhibitors. If you are taking an HIV protease inhibitor and plan to use simeprevir, speak to your doctor about changing your HIV therapy.
  • Pulmonary Arterial Hypertension (PAH) drugs -- sildenafil, tadalafil and vardenafil are used for the treatment of PAH. Janssen recommends that patients start with the lowest dose of these drugs and increase the dose under the close supervision of their doctor.
  • Male sexual dysfunction drugs: sildenafil, tadalafil, vardenafil -- speak to your doctor and pharmacist about the dose of these drugs that is right for you while you are taking simeprevir.
  • Sedatives (sleeping pills) or anti-anxiety drugs -- these drugs must be used cautiously, as simeprevir has the potential to raise their levels in the body, causing side effects. Speak to your doctor and pharmacist about what sedatives are safe for you to use while taking simeprevir.
  • Transplant medicines -- simeprevir can raise levels of cyclosporine, lower levels of tacrolimus or do both to sirolimus. Therefore, monitoring of transplant drugs while you are taking simeprevir is necessary.


Reference

Janssen. Galexos (simeprevir capsules). Product monograph. 18 November 2013.




This article was provided by Canadian AIDS Treatment Information Exchange. It is a part of the publication TreatmentUpdate. Visit CATIE's Web site to find out more about their activities, publications and services.
 

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