Download Med Drugs 7 AntiViral

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Medicines and Drugs 7
Antiviral Drugs (SL + HL)
D7 Antivirals - Assessment Statements
D.7.1
State how viruses differ from bacteria.
!
D.7.2
Describe the different ways in which antiviral drugs work.
!
D.7.3
Discuss the difficulties associated with solving the AIDS
problem.
Some Viral Diseases
chicken pox
cold / influenza
hepatitis
swine flu (H1N1)
Acquired
Immunodeficiency
Syndrome
rabies
Viruses - Background
There are many types of viruses, with a wide range of structures.
These features are common to most viruses:
viral envelope
smaller than bacteria
genetic material (DNA or RNA)
envelope
glycoproteins
core proteins
Viruses (on their own) are non-living.
Viruses vs Bacteria
viruses
bacteria
made of cells?
✘
✔
reproduce on their own?
✘
✔
carry out metabolic processes on
their own?
✘
✔
living or non-living?
non-living
living
how do they cause disease?
“hijack cells” ...
release toxins
Viruses - Life Cycle
Viruses damage cells by invading them and taking over their metabolic processes.
Virus attaches to the cell
surface and enters the cell.
Virus duplicates itself using
its own enzymes and cell
nutrients and energy.
!
Cell lyses, releasing many new
virus particles.!
http://whyfiles.org/2012/biobombs-blast-cancer/
Antiviral drugs target one or more of these steps.
Antiviral Drug Action
Antiviral drugs inhibit one part of the viral life cycle.
✗
✗
1. Block the attachment of the virus to cell surfaces and prevent it from entering cells.
difficult to find drugs that block the attachment of viruses
2. Block viruses from using their own enzymes or the host cell materials to copy viral genetic material and make new virus particles.
e.g. AZT and acyclovir
✗
3. Prevent viruses from exiting host cells (and thereby stopping the spread of the virus).
e.g. Tamiflu
Antiviral Drug Action
Example 1: Acyclovir
used in the treatment of herpes
✗
similar structure to guanosine - a building
block of DNA
adding acyclovir instead of guanosine stops
replication of the viral genetic material
blocks the replication
of viral genetic material
Antiviral Drug Action
Example 2: AZT
(azidothymidine)
used in the treatment of AIDS
✗
inhibits the HIV enzyme
(reverse transcriptase)
needed to copy the viral
genetic material
∴ no new HIV virus particles form
∴ spread of HIV slowed down
targets HIV replication only because RT is not
found in human cells
Antiviral Drug Action
Example 3: Tamiflu
used in the
treatment of
influenza
✗
inhibits the release of
newly formed virus
particles
inhibits the activity of a viral enzyme
(neuraminidase) that acts on cell membranes
∴ spread of the infection is slowed
Antiviral Drug Action
Treating viral diseases is difficult.
1. Viruses are “hidden” within host cells, and are often dormant for a period of time. ∴ difficult for a drug to locate the virus
2. Viruses multiply rapidly.
∴ spread quickly before symptoms appear and
before immune system can respond
3. Viruses have a tendency to mutate easily.
∴ develop resistance to antiviral drugs
4. Viruses cannot be killed with a standard approach
∴ Unlike bacteria with similar metabolic processes, viruses lack subunits that
prohibit a standard approach ∴ Each requires a specially-targeted drug to change virus on a genetic level
Difficulties with the AIDS Pandemic
HIV activity
1. HIV targets a cell in the immune system (helper-T cell) that co-ordinates the immune response.
body is not able to fight infection on its own
2. HIV mutates very rapidly within a single patient.
more new HIV variants produced each year than influenza viruses
3. HIV is dormant for several years after the initial infection.
anti-HIV drugs only target enzymes used during the
replication of new virus particles
4. Drug options are limited.
Difficulties with the AIDS Pandemic
societal and cultural factors
1. anti-HIV drugs are very costly
prevalence of AIDS in developing
regions - 95%
limited access - 8% of people
needing HIV drugs receive it
2. AIDS stigma
prevents people from seeking
testing and/or treatment
compulsory testing for employment
http://hart-hiv.org/author/admin/