Antiviral and Antiparasitic Drugs Flashcards
Why are viruses difficult to target with drugs?
Replicate inside host cells
Use host enzymes to make viral components
Advanced stage before detection.
What kind of treatment does a vaccine provide?
Prophylactic treatment as they are there to prevent viral diseases.
How are neuraminidase inhibitors used to treat viral infections?
Virus released from cell remains attached via sialic acid residues,
Neuraminidase produced by virus breaks bonds
Drug prevents virus infecting other cells
Give some examples of neuraminidase inhibitors and what viruses are they used against.
Oseltamivir, Tamiflu
Used against Influenza A and B
What drugs will inhibit genetic replication and integration of viral infections?
DNA polymerase inhibitors
Reverse Transcriptase (RT) inhibitors.
What are DNA polymerase inhibitors used to treat?
Prevents DNA replication and therefore is used against DNA viruses such as herpes
What are RT inhibitors used to treat?
Prevents RNA –> DNA copies and therefore is used against RNA retroviruses (HIV)
Give an example of a DNA polymerase inhibitor?
Aciclovir:
used against herpes
How does Aciclovir work?
Pro-drug,
Nucleoside analogue of guanine with an altered ribose.
Phosphorylated by viral thymidine kinase (TK) (viral more effective than host TK)
Used to make acyclo GMP
Triphosphate (acyclo GTP) inhibits viral DNA polymerase preventing viral chain extension.
What are the RT inhibitors used to treat?
AIDS
Give some examples of RT inhibitors?
Nucleoside analogue - Lamivudine
Non-nucleoside - Efavirenz
How does an RT nucleoside analogue work (lamivudine)
Analogue of cytosine
Phosphorylated into a triphosphate
Inhibits RT (competition) not DNA polymerase.
Terminates Viral DNA chain.
How do RT non-nucleoside drugs work against AIDS?
Efavirenz:
Active in the form that it is given
Denatures active site of RT enzyme
What kind of drug is used to treat HIV?
Integrase inhibitors
eg. Raltegravir
How does a integrase inhibitor work?
Viral DNA incorporated into chromosomal DNA using viral integrase enzyme
Inhibitor prevents this.
Therefore used in combination with nucleoside RT inhibitors
What are the side effects of Raltegravir?
GI upset.
Hepatitis
How do protease inhibitors work?
Used against AIDS:
HIV mRNA translated into 2 polyproteins - inert.
Cleaved into functional proteins by viral protease.
Therefore inhibitors prevent them becoming active and leave them inert.
What is the main treatment regime for a patient with AIDS?
Highly active antiretroviral Therapy (HAART):
2 Nucleoside RT inhibitors + one of;
Non-nucleoside RT inhibitor, booster protease inhibitor, integrase inhibitor.
What is malaria?
Disease caused by a protozoal bacterial which is a parasite.
What are the 2 ways of infection from the malaria parasite in the liver?
Pre erythrocytic
Exo erythrocytic
Why does the malaria parasite target RBCs?
Uses Hb as a source of energy and amino acids.
Causes blood vessels to rupture (haemolysis) and leads to fever.
The parasite produces proteins on the surface of the RBCs which bind to endothelium and causes blood vessels to clog.
What are some various parasite species of malaria?
Plasmodium falciparum (malignant malaria)
P. vivax, P. Ovale (benign malaria)
What are the sites of action of antimalarial drugs?
Haem polymerase inhibitors:
Enzyme present in lysosome of parasite.
Converts toxic haem to haemozoin
These drugs inhibit this so haem is toxic to parasite.
No effect on exoerythrocytic phase
What are some examples of antimalarial drugs?
Chloroquine
Quinine
Mefloquine
What is Artemisinin?
Synthetic antimalarial drug used to treat acute phase of infection.
Important in treating Pl. falciparum
How does Artemisinin work to treat malaria?
Drug is activated by haem causing free radicals.
The free radicals bind to and modify proteins causing damage to membranes within the parasite.
What points doe primaquine work at?
treatment in the liver
Prevention of transmission
