Antivirals for hepatitis B and C: Nursing pharmacology

Viral hepatitis is the inflammation of the liver caused by hepatitis viruses A, B, C, D, or E. Out of these, chronic hepatitis caused by hepatitis B virus, or HBV, and hepatitis C virus, or HCV, can be treated with antiviral medications.

Now, chronic HBV infection can be treated with a class of antiviral medications called NRTIs, which include nucleotide reverse transcriptase inhibitors like adefovir and tenofovir, as well as nucleoside reverse transcriptase inhibitors like entecavir; these medications are administered orally.

On the other hand, chronic HCV infection can be treated with antiviral medications that target different components of the virus, so they’re typically used in combination; these include nucleotide polymerase inhibitors like sofosbuvir, as well as nucleoside analogues like ribavirin, both of which are taken orally.

Finally, there’s a third class of medications that can be used to treat both chronic HBV and HCV; these include interferons like peginterferon alfa-2a, which is administered by subcutaneous injection.Now, once administered, all of these antivirals have a different mechanism of action.

NRTIs used to treat hepatitis B act by inserting into the replicating viral DNA. As a result, viral DNA synthesis is halted, ultimately stopping viral replication.

On the other hand, medications used to treat hepatitis C work in different ways, inhibiting different viral proteins or enzymes required for viral replication.

Interferons, on the other hand, induce the innate antiviral immune response that helps kill off cells that are infected by the virus.Now, clients taking NRTIs for hepatitis B infection can have side effects.

All these medications come with a boxed warning for severe, acute hepatitis exacerbations on discontinuation of therapy.

These medications also cause lactic acidosis, which is a boxed warning for adefovir and entecavir, as well as severe hepatomegaly with steatosis; and a risk for individuals with concurrent HIV infection, that refers to the risk of developing HIV resistance to these agents.

Other common side effects for these medications include hepatotoxicity and increased serum transaminase levels, as well as hematuria.

Finally, adefovir can also cause fatigue; headache; muscle weakness; back pain and joint pain; and gastrointestinal toxicity, which can manifest as nausea, abdominal pain, diarrhea or vomiting; while tenofovir may cause nephrotoxicity.Now let’s switch gears and look at the side effects of medications used to treat hepatitis C.

All these medications come with a boxed warning for HBV reactivation in clients with concomitant HBV infections, which can cause potentially life-threatening fulminant hepatitis.

Ribavirin also has two more boxed warnings, for use during pregnancy and for an increased risk of causing hemolytic anemia.

Another thing to bear in mind is that hepatitis C medications are usually part of a multi-drug regimen, so common side effects refer to those occurring with combination therapy.

These include neurotoxicity, like fatigue, headache, insomnia and dizziness; dermatological reactions, like rashes, pruritus and eczema; as well as flu-like symptoms, myalgia and muscle weakness.

Multidrug regimens containing ribavirin can also cause alopecia. Gastrointestinal toxicity is also a common side effect of these medications, and it can manifest as nausea, diarrhea, anorexia and subsequent weight loss.Finally, let’s go over the side effects of peginterferon alfa 2a.

First up, it comes with a boxed warning for aggravating life-threatening neuropsychiatric, autoimmune, infectious and ischemic conditions.

Other common side effects include flu-like symptoms, fatigue, fever, myalgia, and headache, as well as injection site reaction; but it can also cause gastrointestinal toxicity, with nausea, vomiting, diarrhea or abdominal pain; and dermatological side effects like rashes, pruritus or alopecia.

As far as contraindications go, NRTIs should be used cautiously during breastfeeding, pregnancy, in children and the elderly, as well as those with severe renal disease.

Entecavir in particular should be used with caution in clients with impaired hepatic function. Also remember that all clients with hepatitis B should be tested for an HIV infection before starting treatment with an NRTI.Medications used to treat hepatitis C should be used cautiously during pregnancy, breastfeeding, and in clients with hepatic disease, renal disease or diabetes.

Ribavirin is also contraindicated in clients with autoimmune hepatitis and decompensated cirrhosis. Now, since sofosbuvir is metabolized by cytochrome P450 in the liver, they shouldn’t be used with potent cytochrome inducers like rifampin or St.

John’s wort, since they can decrease the medications’ level and effectiveness. Finally, be extra careful when sofosbuvir is used in combination with amiodarone, since the combo could cause severe bradycardia.Now, peginterferon alfa 2a is contraindicated during pregnancy and breastfeeding, and should be used with caution in clients with pre-existing cardiac disease, severe renal or hepatic impairment, myelosuppression, and compromised central nervous system function.

When taken in combination, interferons increase theophylline levels. In addition, the risk of neutropenia or anemia is increased when taken with zidovudine.All right, when caring for a client with chronic hepatitis B infection who has been prescribed the NRTI tenofovir, begin your assessment by asking about their current symptoms, such as fatigue, anorexia, nausea, vomiting, or dark urine.

Then, assess their vital signs and observe their skin, eyes, and mucous membranes for yellowing. Lastly, review your client’s most recent laboratory test results, especially renal and liver function tests, bilirubin, albumin, PT, HBsAg, and urinalysis; as well as the results of diagnostic tests, such as a liver scan or biopsy.

Moving on to client education, explain to your client that tenofovir helps to lower the amount of the hepatitis B virus in their body, but it will not completely eliminate the infection, and they can still transmit the virus to others.

Then, instruct them to take their medication once each day with a full glass of water, with or without food. If your client is taking the powder form, instruct them to measure their medication using the scoop that’s supplied with the medication, and to mix it with 2 to 4 ounces of soft food, like yogurt or applesauce, and to take it right after mixing.

Be sure to emphasize the importance of adhering to their medication regimen, and explain that their infection can get worse if the medication is discontinued.

In addition, let your client know about the importance of routine follow-up blood tests to evaluate for side effects. Next, let your client know about some side effects they could experience during treatment, such as neurological side effects like headache, dizziness, and insomnia; as well as gastrointestinal side effects, like nausea, flatulence, or diarrhea; and advise them to contact their healthcare provider if these don’t resolve.

In addition, stress the importance of immediately reporting symptoms of hepatotoxicity, including fatigue, anorexia, abdominal pain, dark urine, or yellowing of the eyes or skin; as well as symptoms of nephrotoxicity, which could present as decreased urine output, difficulty urinating, blood in the urine, or weight gain; and symptoms of lactic acidosis, which could manifest as fast breathing or heartbeat, severe fatigue or dizziness, and muscle pain or cramps.

In addition, provide education about lifestyle modifications your client can implement to promote overall health and to support their liver health.

Advise them to alway get the annual influenza vaccine, and prompt them to get vaccinated against hepatitis A as well. If your client smokes, counsel them about smoking cessation; and remind them that consuming alcohol can make their liver damage worse.

Also, advise your client to check with their healthcare provider before taking any over the counter medication, since many of these contain acetaminophen, which can further damage their liver.

Lastly, let your client know they should have regular screenings for liver cancer.Finally, while caring for a client on antiviral therapy for hepatitis, continue to assess them for side effects, and evaluate for the desired therapeutic response, including improvement in their chronic hepatitis symptoms.

All right, as a quick recap… Chronic viral hepatitis is treated by antiviral medications, such as the NRTIs adefovir, tenofovir, or entecavir for HBV infection; sofosbuvir or ribavirin for HCV infection; and peginterferon alfa-2a for both HBV and HCV.

These medications can cause side effects such as hepatotoxicity, nephrotoxicity, and lactic acidosis, as well as an exacerbation of their infection if the medication is discontinued.

While caring for a client on antiviral therapy for hepatitis, nursing considerations include performing a baseline assessment, monitoring the client for side effects, and evaluating for the desired therapeutic response.

Client teaching is focused on medication adherence, engaging in safe behaviors and lifestyle modifications,