McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

AGENTS FOR HERPES AND CYTOMEGALOVIRUS

Evaluation

KEY POINTS ■■ Viruses are segments of RNA or DNA enclosed in a protein coat. ■■ A virus must enter a human cell to survive, making it difficult to treat without serious toxic effects for the host. ■■ Antiviral drugs that prevent the viral replication of respiratory viruses can be used to prevent or treat influenza A or other respiratory viruses. ■ ■ Monitor person’s response to the drug (prevention of respiratory flu-like symptoms; alleviation of flu-like symptoms). ■ ■ Monitor for adverse effects (changes in orientation and affect, blood pressure, urinary output). ■ ■ Determine the effectiveness of the teaching plan (person can name the drug, dosage, possible adverse effects to watch for and specific measures to help to avoid or minimise adverse effects). ■ ■ Monitor the effectiveness of comfort and safety measures and compliance with the regimen.

Herpes viruses account for a broad range of conditions, including cold sores, encephalitis, shingles and genital infections. Cytomegalovirus (CMV) , although slightly different from the herpes virus, can affect the eye, res- piratory tract and liver and reacts to many of the same drugs. Antiviral drugs used to combat these infections include aciclovir ( Zovirax ), cidofovir ( Vistide ), fam- ciclovir ( Famvir ), foscarnet ( Foscavir ), ganciclovir ( Cymevene ), valaciclovir ( Shilova , Vaclovir ) and val- ganciclovir ( Valcyte ). See Table 10.2. Therapeutic actions and indications Drugs that combat herpes and CMV inhibit viral DNA replication by competing with viral substrates to form shorter, non-effective DNA chains (see Figure 10.2). This action prevents replication of the virus, but it has little effect on the host cells of humans because human cell DNA uses different substrates. These antiviral agents are indicated for treatment of the DNA viruses herpes simplex, herpes zoster and CMV. Research has shown that they are very effective in immunocompro- mised individuals, such as individuals with AIDS, those taking immunosuppressants and those with multiple infections. See Table 10.2 for usual indications for each of these agents.

KEY POINTS

TABLE 10.2

DRUGS IN FOCUS Agents for herpes virus and cytomegalovirus (CMV)

Drug name

Dosage/route

Usual indications

5–10 mg/kg q 8 hours or 200–800 mg 3–5 times daily for 5–10 days 5 mg/kg IV (over 1 hour) once weekly for 2 weeks, then 5 mg/kg IV every 2 weeks Herpes zoster: 250 mg PO q 8 hours for 7 days Genital herpes: 125 mg b.d. PO for 5 days Adult: 40–60 mg/kg q 8–12 hours IV given as a 2-hour infusion Paediatric: safety and efficacy not established Adult: 5 m/kg q 12 hours IV given over 1 hour for 14–21 days, then over 1 hour daily 7 days/ week or 6 mg/kg per day for 5 days/week for prophylaxis Herpes zoster: 1 g PO t.d.s. for 7 days Genital herpes: 500 mg b.d. PO for 5 days 900 mg PO b.d. for 21 days, then 900 mg PO once a day for maintenance; reduce dose with renal impairment

Treatment of herpes virus infections

aciclovir (Zovirax, Lovir)

cidofovir (Vistide)

Treatment of CMV retinitis in people with AIDS Treatment of herpes virus infections such as herpes zoster or shingles and for recurrent episodes of genital herpes Treatment of CMV and aciclovir-resistant mucocutaneous herpes simplex infections in immunocompromised individuals Long-term treatment and prevention of CMV infection

famciclovir (Ezovir, Famvir, Favic)

foscarnet (Foscavir)

ganciclovir (Cymevene, Vitrasert)

valaciclovir (Shilova, Vaclovir) valganciclovir (Valcyte)

Treatment of herpes zoster and recurrent genital herpes; cold sores (herpes labialis) Treatment of CMV retinitis in people with AIDS