McKenna's Pharmacology for Nursing, 2e

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P A R T 3  Drugs acting on the immune system

■■ BOX 18.5  Vaccines and biological weapons

many cervical cancers. This vaccine is given in a series of three injections to achieve full protection. In many cases, antibody titres (levels of the antibody in the serum) can be used to evaluate a person’s response to an immunisa- tion and determine the need for a booster dose. Due to recent events and the fear of terrorist activi- ties, concern has risen about the use of various diseases as biological weapons. Box 18.5 discusses vaccines and the use of biological weapons. Therapeutic actions and indications Vaccines stimulate active immunity in people who are at high risk for development of a particular disease. The The events of September 11 2001 and the subsequent war on terrorism have heightened awareness of several diseases that might be in development as biological weapons. Anthrax, plague, tularaemia, smallpox, botulism and a variety of viral haemorrhagic fevers are all considered to be likely biological warfare weapons. Anthrax An imported vaccine is available in Australia made from inactivated cell-free filtrate of a virulent strain of the anthrax bacillus. It is available only for military use. Active production stopped in 1998, but production and supply issues were made high priorities. Ciprofloxacin and, in sensitive cases, doxycycline and penicillins are effective in treating postexposure cases. The vaccine is given and repeated in 2 and 4 weeks, along with the appropriate antibiotic, to people who have been exposed. Plague Plague is easily spread from person to person, and without treatment can progress rapidly to respiratory failure and death. There is currently no vaccine for plague; a whole-cell vaccine that was used for many years is no longer available. Research is ongoing using a pneumonic plague vaccine that has successfully protected animals. Several drugs have been found to be life-saving with plague—streptomycin, doxycycline, ciprofloxacin and chloramphenicol. Smallpox Smallpox was considered eradicated since no new cases had been seen in 20 years. Smallpox is highly transmissible and has a 30% mortality rate in unvaccinated people. Immunisation against smallpox ended in the 1970s. There is now a commercially available vaccine, but use is somewhat limited because of questions raised during studies of the vaccine. It is given to military personnel and people thought to be at high risk. It is currently thought that the vaccine is no longer effective after 20 years, although there is no definite evidence that previously

vaccine needed for a person depends on the exposure that person will have to the pathogen. Exposure is usually determined by where the person lives and their travel plans, and work or family environment exposures. Vaccines are thought to provide lifelong immunity to the disease against which the individual is being immunised. Table 18.1 lists the various vaccines available along with usual indications. Pharmacokinetics There is no pharmacokinetic information on these bio- logicals, which are treated like endogenous antibodies in the body. No vaccines are currently available for these agents, although the United States Army has had success with a vaccine for Junin. Ribavirin has been effective in some cases of Lassa fever and has been effective orally for postexposure prophylaxis. It is being studied for effectiveness with these other viruses. Currently there is no established treatment and this area is one of the highest priorities for combating possible biological warfare. vaccinated people have no protection. The smallpox vaccine uses live virus, placed in punctures made in the skin. After exposure, vaccination given within the first 3 to 4 days can prevent the disease. If it has been 7 days or longer since exposure, the vaccine and a vaccinia immune globulin should be used, if any are available. So far no drugs are thought to be effective in treating smallpox. Early studies have, however, shown cidofovir ( Vistide ) to be effective in vitro. Tularaemia Tularaemia in an aerosolised form can cause systemic and respiratory illness with a 35% mortality rate. It is not passed from person to person. There is no vaccine available, but doxycycline and ciprofloxacin can be used after exposure, and gentamicin has been effective after symptoms appear. Botulism Botulism, produced by Clostridium botulinum , can be aerosolised or used to contaminate food. The toxin it produces causes cranial nerve palsies that can result in muscle paralysis and respiratory failure. Antitoxin is also available for people with specific exposures, and research is ongoing with an equine antitoxin effective against all seven serotypes of botulism that is thought to cause fewer hypersensitivity reactions than what is currently available. Viral haemorrhagic fever Lassa, Marburg, Junin and Ebola viruses cause haemorrhagic fevers with mortality rates as high as 90%.