Thursday, May 1, 2008
Agents for HIV and AIDS
The human immunodeficiency virus (HIV) attacks the helper T cells within the immune system. This virus enters the helper T cells and multiplies within the cell. When the cell ruptures many new viruses are released to attack other helper TY cells. The end result is that the immune system loses an important monitor that propels the immune reaction into full force when the body is invaded.
Reverse Transcriptase Inhibitors
The reverse transcriptase inhibitors bind directly to HIV reverse transcriptase, blocking both RNA- and DNA-dependent DNA polymerase activities. They prevent the transfer of information that would allow the virus to replicate and survive.
1. Delavirdine (Rescriptor) – must be used in combination therapy regimens, because resistant strains develop rapidly when it is used alone. It is rapidly absorbed from the GI tract, with peak levels occurring within 1 hour.
2. Efavirenz (Sustiva) – is used in adults and in children in combination with other anti retrovural agents. It is absorbed rapidly from the GI tract, reaching peak levels in 3 to 5 hours. It is metabolized in the liver by the cytochrome P450 system and is excreted in the urine and feces with a half-life of 52 yo 76 hours.
3. Nevirapine (Viramune) – is recommended for use in adults and children. After rapid GI absorption, nevbirapine is metabolized by the cytochrome P450 system in the liver.
The protease inhibitors block protease activity within the HIV virus. Protease is essential for the maturation of infectious virus, without it an HIV particle is immature and non effective.
1. Amprenavir (Agenerase) – was approved in 1999 for the treatment of adults and children with HIV in combination with other antiretroviral agents. It is rapidly absorbed from the GI tract, reaching peak levels in 1 to 2 hours.
2. Indinavir (Crixivan) – is available for treatments of adults with HIV rapidly absorbed from the GI tract reaching peak levels in 0.8 hours.
3. Lopinavir (Kaletra) – is a fixed combination drug that combines lopinavir and ritonavir. This drug is approved for used in adults and children in combination with other antiretroviral agents for the treatment of HIV infection.
4. Nelfinavir (Viracept) – must be given in combination with other drugs and can be used in the treatment of children with HIV.
5. Ritonavir (Norvir) – can be used alone and is available for use in adults and children.
6. Saquinavir (Fortovase, Invirase) – is used in combination regimens for adults.
Nucleosides interfere with HIV replication by inhibiting cell protein synthesis, leading to viral death.
1. Abacavir (Ziagen) – is used in combination therapy in adults and children.
2. Didanosine (Videx) – is used to treat advanced infections in adults and in children.
3. Lamnivudine (Epivir) – is recommended specifically for use with other antiretroviral agents as an oral solution.
4. Stavudine (Zerit) – is recommended specifically for used with other retroviral agents.
5. Tenafovir (Viread) – is a new drug that affects the virus at a slightly different point of replication- a nucleotide that becomes a nucleoside.
6. Zalcitabine (Hivid) – is used to treat advanced cases of HIV/AIDS in adults.
7. Zidovudune (Retrovir) – was one of the first drugs found to be effective in the treatment of AIDS.
Therapeutic Actions and Indications
The antiviral agents used to treat HIV and AIDS operate at various point in the life cycle of the virus and results in its death or inactivation. Use of these drugs in combination can affect more viral particles and reduce the number of mutant viruses that are formed and spread to non infected cells.
Contraindications and Cautions
Because these drugs are used in the treatment of a potentially fatal with no known cure, there are no true contraindications to their use. Zidovudine is the drug of choice during pregnancy to block maternal transmission of the virus. Cautions should be used with known allergies to any of these drugs, with hepatic or renal dysfunction which could lead to increased drug levels and toxicity and with pregnancy or lactation because of potential adverse effects on the neonate.
The adverse effects reported with the used of these drugs often are not distinguishable from the effects of ongoing disease process. Adverse effects are often reported include the CNS effects of headache, dizziness and myalpatic toxicity related to direct drug effects on the liver, fever and flu-like symptoms, rash and bone marrow depression including a granulocytosis and anemia.
The patient receiving a DNA-active antiviral agent may have the following nursing diagnoses related to drug therapy:
· Acute pain related to GI, CNS, local effects of drugs
· Disturbed sensory perception related to CNS
· Deficient knowledge regarding drug therapy
· Monitor renal and hepatic function before and periodically during therapy to detect renal or hepatic function changes.
· Ensure that the patient takes the complete course of the drug regimen and takes all drugs included in a particular combination.
· Administer the drug around the clock, if indicated, to provide the critical concentration needed for the drug to be effective.
· Monitor nutritional status if GI effects are severe, and take appropriate action to maintain nutrition.
· Stop drug if severe rush occurs, especially if accompanied by blisters, fever, and so on, to advert potentially serious reactions.
· Provide safety precautions (e.g., the use of side rails, appropriate lighting, orientation, assistance) if CNS effects occur, to protect patient from injury.
· Teach the patient about the drugs prescribed, to enhance patient knowledge about drug therapy and to promote compliance. Include as a teaching point the fact that these drugs do not cure the disease and therefore appropriate precautions should still be taken to prevent transmission.
The patient should:
Have regular medical care.
Have periodic blood tests, which are necessary to monitor the effectiveness and toxicity of the drug.
Realize that GI upset, nausea, and vomiting may occur but the efforts must be taken to maintain adequate nutrition.
Avoid driving and hazardous tasks if dizziness or drowsiness occurs.
Report extreme fatigue, severe headache, difficulty breathing, or severe rash ot a heath care provider.
· Monitor patient response to the drug.
· Monitor for adverse effects.
· Evaluate the effectiveness of the teaching plan.
· Monitor the effectiveness of comfort and safety measures.
Locally Active Antiviral Agents
1. Idoxuridine (Herplex) – which is applied directly to the eye and is used to treat herpes simplex keratitis.
2. Imiquimod (Aldara) – which is appli9ed locally for the treatment of genital and perinatal warts.
3. Formivirsen (Vitravene) – which is injected into the eye to treat CMV retinitis to patients with AIDS.
4. Ganciclovir (Vitrasert) – which is implanted into the eye every 5 to 8 months for treatment of patients with CMV retinitis.
5. Penciclovir (Denavir) – which is applied locally for the treatment of herpes labialis (cold sores) on the face and lips.
6. Trifluridine (Vitroptic) – which is applied locally to treat herpes simplex infections in the eye.
7. Vidarabine (Vira-A) – which is used locally to treat herpes simplex infections of the eye that are not responsive to idoxuridine.
Therapeutic Actions and Indications
These antiviral agents act on viruses by interfering with normal viral replication and metabolic processes. They are indicated for specific local viral infections.
Locally active antiviral drugs are not absorbed systematically but caution should be used in patients with known allergies reactions to any topical drugs.
Because these drugs are not absorbed systematically, the adverse effects of most commonly reported are local burning, stinging, and discomfort. These effects usually occur at the time of administration and pass with time.
The patient receiving a topical antiviral drug may have the following nursing diagnoses related to drug therapy:
· Acute Pain related to GI, CNS, local effects of drug
· Deficient Knowledge regarding drug therapy
· Ensure proper administration of the drug to improve effectiveness and decrease risk of adverse effects.
· Stop the drug if severe local reaction occurs or if open lesions occur near the site of administration, to prevent systemic absorption.
· Monitor patient response to the drug.
· Monitor adverse effects.
· Evaluate effectiveness of the teaching plan.