McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

KEY POINTS ■■ The HIV virus infects helper T cells, leading to a loss of immune function and the development of opportunistic infections. ■■ Drugs used to treat HIV are usually given in combination to affect the virus at various points in the body: non-nucleoside and nucleoside reverse transcriptase inhibitors block RNA and DNA activity in the cell; protease inhibitors prevent maturation of the virus; fusion inhibitors prevent the entry of the virus into the cell; CCR5 coreceptor antagonists prevent the virus from reacting with the receptor on the cell membrane, preventing its entry into the cell; and integrase inhibitors block an enzyme essential for formation of the provirus within the cell, leading to decrease in the number of viruses. ■■ People taking drugs to treat HIV need to take all of the medications continuously as prescribed and take precautions to prevent the spread of the disease to others. ANTI-HEPATITIS B AND C AGENTS Hepatitis B and C are serious-to-potentially fatal viral infections of the liver. The hepatitis B and C virus can be spread by blood or blood products, sexual contact or contaminated needles or instruments. Healthcare workers are at especially high risk for contracting hepa- titis infection due to needle stick injuries. Hepatitis B has a higher mortality than other types of hepatitis. Individ- uals infected may also develop a chronic condition or to stop the replication of HIV, to control AIDS and to maintain the functioning of your immune system. A schedule will be plotted out to show exactly when to take each of the drugs. It is very important that you take all of the drugs and that you adhere to this schedule to ensure that the drugs can be effective and reduce the development of resistant strains of the virus. These drugs are not a cure for HIV, AIDS or ARC. Opportunistic infections may occur and regular medical follow-up should be sought to deal with the disease. These drugs do not reduce the risk of transmission of HIV to others by sexual contact or by blood contamination; use appropriate precautions. Common effects of these drugs include the following: • Dizziness, weakness and loss of feeling: Change positions slowly. If you feel drowsy, avoid driving and dangerous activities. • Headache, fever, muscle aches: Analgesics may be ordered to alleviate this discomfort. Consult with your healthcare provider. KEY POINTS

become a carrier. In the past, hepatitis B and C were treated with interferons (see Chapter 17). In 2004 and 2005, adefovir ( Hepsera ) and entecavir ( Baraclude ) were approved specifically for treating chronic hepatitis B. In 2006, another nucleoside reverse transcriptase inhib- itor, telbivudine ( Sebivo ), was found to be very effective in preventing viral replication in people with active hepatitis B. More recently, two drugs specifically for hepatitis C, boceprevir ( Victrelis ) and telaprevir ( Incivo ) have become available. Therapeutic actions and indications Adefovir, entecavir and telbivudine are indicated for the treatment of adults with chronic hepatitis B who have evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases or histologically active disease. The drugs inhibit reverse transcriptase in the hepatitis B virus and cause DNA chain termination, leading to blocked viral replication and decreased viral load (see Table 10.4). Boceprevir and telaprevir block the HCV NS3 serine protease essential for replication of the hepatitis C virus. Pharmacokinetics These drugs are rapidly absorbed from the GI tract, with peak effects occurring in 0.5 to 1.5 hours (entecavir), 0.5 to 4 hours (adefovir) and 1 to 4 hours (telbivudine). Entecavir and adefovir are metabolised in the liver and excreted in the urine. Telbivudine is excreted unchanged in the urine. Adefovir has a half-life of 7.5 hours; ente- cavir has a half-life of 128 to 149 hours; and telbivudine has a half-life of 40 to 49 hours. It is not known whether blood tests, which are needed to monitor the effects of these drugs on your body and to adjust doses as needed. • Tell any doctor, nurse, or other healthcare provider that you are taking these drugs. • Keep these drugs and all medications out of the reach of children. Do not share these drugs with other people. • Nausea, loss of appetite, change in taste: Small, frequent meals may help. It is important to try to maintain good nutrition. Consult your healthcare provider if this becomes a severe problem. • Report any of the following to your healthcare provider: excessive fatigue, lethargy, severe headache, difficulty breathing or skin rash. • Avoid over-the-counter medications and herbal therapies; many of them interact with your drugs and may make them ineffective. If you feel that you need one of these, check with your healthcare provider first. • Schedule regular medical evaluations, including