Antivirals Flashcards
Describe a virus
Intracellular
Small
DNA/RNA – replication uses hosts metabolic machinery
How do antivirals work?
Virostatic
Stop replication of new viruses
Host immune response required to clear virus
What agents can inactivate viruses?
Non-organic = detergents, chorine-based
Organic solvents = ether, alcohol
Radiation = UV, laser
Cryotherapy
Outline the mechanisms of viral replication
Attachment = virus must attach to host cell
Penetrating = direct fusion with cell membrane, endocytosis, pH mediated fusion
Uncoating = virion disassemble
RNA/DNA replication/protein synthesis = viral proteins and messages are expressed
Assembly = new virions are formed
Release = via lysis or budding
Describe immunomodulators
Replace deficient host immunity = Igs
Enhance host immunity = vaccine
What drugs are given to treat influenza A and B
TAMIFLU, ZANAMIVIR
MECHANISM = neuraminidase inhibitor - blocks release of assembled virions from the host cell
RESISTANCE = mutation of neuraminidase enzyme – tamiflu cant bind
(Note – yearly vaccinations for those at risk)
What drugs are given to treat herpes
ACICLOVIR
MECHANISM = purine/pyramidine analogues, phosphorylated by viral thymidine kinase - Inhibit viral DNA synthesis
RESISTANCE = thymidine kinase enzyme mutation, in the virus which stops acyclovir cant bind and act as false substrate
(Note – aciclovir only effective during acute phase, symptomatic)
What drugs are given to treat cytomegalovirus?
GANCICLOVIR
MECHANISM = purine/pyramidine analogues, phosphorylated by enzyme - Inhibit viral DNA synthesis
ADRs = myelosupressive, carcinogenic/teratogenic
What drugs are used to treat hepatitis B/C?
SOFOSBUVIR = blocks action of HCV viral polymerase to prevent production of new virus
INTERFERON ALPHA = stimulate proteins to enhance cellular resistance to viral infection
What drugs are used to treat chronic hepatitis C?
RIBAVIRIN
MECHANISM = guanosine analogue: inhibits guanosine triphosphate formation preventing viral messenger RNA capping - prevents assembly of viral genome/DNA
ADRs = anaemia, teratogenic
What drugs treat HIV?
NRTIs = nucleoside RT inhibitors – inhibits DNA polymerase
NNRTI = non-nucleoside reverse transcriptase inhibitors - inhibits RT
PI = protease inhibitors – block cleavage preventing virion formation
Why is antiviral drug resistance testing needed?
Optimise clinical outcomes, QoL, longevity of pt
Save costs and adverse effects of ineffective therapy
Reduce pool of drug resistant viruses
How do we test for antiviral drug resistance?
Incubate virus with various levels of drug
Look for specific sequencing/genotype mutation
