3.14 Antivirals

Unlike the complex structure of fungi or protozoa, viral structure is simple.  There are several subclasses of antiviral medications: antiherpes, antiinfluenza, anti-hepatitis, and antiretrovirals.  Each subclass will be discussed in more detail below.  See Figure 3.10^[1] for images of viruses.

Subclass: Antiherpes

Indications: Acyclovir (Zovirax) and its derivatives are frequently used for the treatment of herpes and varicella virus infections, including genital herpes, chickenpox, shingles, Epstein-Barr virus infections, and cytomegalovirus infections.

Mechanism of Action: Acyclovir causes termination of the DNA chain during the viral replication process. Acyclovir can be administered either topically or systemically, depending on the infection.^[2]

Special Administration Considerations: Acyclovir use may result in nephrotoxicity.

Patient Teaching & Education: Patients who are being treated with antiviral therapy should be instructed about the importance of medication compliance. They may also experience significant fatigue, so periods of rest should be encouraged.^[3]

Subclass: AntiInfluenza

Indications: Tamiflu (oseltamivir) is used to target the influenza virus by blocking the release of the virus from the infected cells.

Mechanism of Action: Tamiflu prevents the release of virus from infected cells.

Special Administration Considerations: This medication does not cure influenza, but can decrease flu symptoms and shorten the duration of illness if taken in a timely manner. Patients are prescribed the medication for prophylaxis against infection, known exposure, or to lesson the course of the illness. If patients experience flu-like symptoms, it is critical that they start treatment within 48 hours of symptom onset.

Patient Teaching & Education: Patients who are being treated with antiviral therapy should be instructed about the importance of medication compliance. They may also experience significant fatigue, so periods of rest should be encouraged.^[4]

The influenza virus is one of the few RNA viruses that replicates in the nucleus of cells. Antivirals block the release stage. See Figure 3.11.^[5]

Subclass: Antiretrovirals

Viruses with complex life cycles, such as HIV, can be more difficult to treat. These types of viruses require the use of antiretroviral medications that block viral replication. (See Figure 3.12 to view the viral replication process of HIV.) ^[6] Additionally, antiretrovirals fall under the class of antiviral medications.

Indications: Antiretrovirals are used for the treatment of illnesses like HIV.

Mechanism of Action: Antiretrovirals impede virus replication.

Special Administration Considerations:  Many antiretrovirals may impact renal function; therefore, the patient’s urine output and renal labs should be monitored carefully for signs of decreased function.

Patient Teaching & Education: Patients who are being treated with antiviral therapy should be instructed about the importance of antiretroviral compliance. They may also experience significant fatigue, so periods of rest should be encouraged.^[7]

Now let’s take a closer look at the medication grids for the subclasses of antivirals in Table 3.14a-d.^[8]

Tables 3.14a Acyclovir Medication Grid

Tables 3.14b Oseltamivir Medication Grid

Tables 3.14c Adefovir Medication Grid

Tables 3.14d Lamuvadine-Zidovudine Medication Grid

Critical Thinking Activity 3.14a

Using the above grid information, consider the following clinical scenario question:

A patient is prescribed oseltamivir (Tamiflu) for influenza symptoms. The patient states to the nurse, “I hope this medication works quickly! I have felt lousy for the past 5 days!” What is the nurse’s next best response?

Note: Answers to the Critical Thinking activities can be found in the “Answer Key” sections at the end of the book.