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Pharmacology > SPR L7 Antimicrobials 3 > Flashcards

SPR L7 Antimicrobials 3 Flashcards

1
Q

Outcomes

A
  1. Common classes of antibiotic
  2. Other important antibiotic classes
  3. Other anti-microbials

–Anti-virals

–Anti-fungals

(in this lecture)

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2
Q

Disease Outcomes

A

Antiviral agents which act on:-

–virus absorption, entry and uncoating

–integration of DNA

–nucleic acid synthesis

–transcription

–post translational processing

–protein assembly

–virus budding and spread

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3
Q

Treatment Perspective

Give examples of

  1. Antiviral treatment
  2. Antifungal treatment
A
  1. Herpesvirus Rx – Aciclovir (famciclovir)

Influenza Rx – Oseltamivir

(HIV / Hep B – Specialist areas)

  1. Nystatin

Fluconazole

Amphotericin

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4
Q

Viruses

Describe viruses, what do they need, and what does treatment need to target?

A

Obligate intracellular parasites

Need the host synthetic functions

Therefore anti-virals need to be specific for viral functional pathways (not host)

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5
Q

The Life Cycle of an Animal Virus

Outline the cycle

A

(a) Adsorption or docking with the host receptor protein
(b) Entry into the host cytoplasm
(c) Biosynthesis of viral components
(d) Assembly of viral components into complete viral units
(e) Budding from the host cell.

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6
Q

Herpesvirus infection

  1. What do herpes viruses include?
  2. What is the treatment?
  3. When will aciclovir be activated
A
  1. –Herpes simplex viruses 1 and 2

–Varicella zoster virus

–Epstein-Barr virus

–Cytomegalovirus

  1. Aciclovir

–Nucleoside analogue (Guanosine)

–Inhibits viral DNA synthesis

–2 point selective toxicity: viral thymidine kinase and viral DNA polymerase

Clever: uninfected human cell will be left alone, aciclovir isn’t activated

  1. Will only be activated (phosphorylated) in an infected cell. Resistance occurs on the basis of deficient thymidine kinase activity (use foscarnet instead)
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7
Q

Aciclovir

  1. Describe the topical preparation
  2. Describe the Oral preparation
  3. Describe the IV preparation
A
  1. High local concentration, Not absorbed systemically
  2. 20% bioavailability, T ½ = 3-4 hours (if normal renal function), Typically 200mg x5 per day
  3. 10mg/kg 8-hrly treatment for HSV encephalitis, Or if immunocompromised
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8
Q

Varicella Zoster
(Shingles)

Oral aciclovir is given, what effect does it have?

A

Higher doses needed than for HSV

Shortens number and duration of lesions

Tends to reduce the associated neuralgia that follows the infection

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9
Q

Aciclovir

What are the main adverse effects?

A
  • Nausea / GI upset
  • Headache
  • Nephrotoxicity / Neurotoxicity
    • Mainly with the larger doses given iv
    • Avoided by adequate hydration and slow ivi
  • Must reduce doses in renal impairment
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10
Q

Famciclovir

  1. What type of drug is it?
  2. What is it a pro-drug of?
  3. How does it act?
  4. What does it achieve?
  5. What is it’s oral bioavailability?
  6. What is the dosing regimen? Why is this beneficial?
A
  1. Another Guanosine analogue
  2. Pro-drug of penciclovir
  3. Similar in action to aciclovir
  4. Achieves higher cell conc and more prolonged effect
  5. 70% oral bioavailability
  6. Only need 2-3 times per day - therefore better adherance
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11
Q

Influenza viruses

What are the main treatments?

A

Vaccination

Oseltamivir –Neuraminidase inhibitor

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12
Q

Oseltamivir

  1. What type of drug is this?
  2. What is neuraminidase?
  3. What is the duration like?
  4. What about the complication rates?
  5. What are the adverse effects?
A
  1. Neuraminidase inhibitor. Pro-drug. Activated by liver on 1st pass
  2. an essential viral glycoprotein for virus replication and release. High homology of neuraminidase in influ A + B.
  3. Slight reduction in duration (1 day)
  4. Slight reduction in complication rates??
  5. Nausea / GI upset / headache common
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13
Q
  1. What is the treatment for Herpesvirus?
  2. What is the treatment for Influenza Virus?
A
  1. Aciclovir (famciclovir)
  2. Oseltamivir
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14
Q

Antifungal Agents

  1. When are they usually very toxic?
  2. How are they used?
  3. Give examples of infections they treat
  4. When do we ue systemic Rx?
    1. Give examples
A
  1. Usually very toxic agents if given systemically
  2. Unlike antibiotics, tend to use topically for most superficial fungal infections
  3. Oral candida and Tinea
  4. Only when patient is systemically unwell or immunocompromised
    1. Aspergillosis and Systemic candidiasis
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15
Q

Antifungal Agents

Give examples of these

A
  • Amphotericin
  • Nystatin
  • Fluconazole
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16
Q

Antifungal Agents

Amphotericin (B)

  1. What type of drug is it?
  2. Why does it need to be given IV?
  3. It is nearly insoluble in water - what does this result in
  4. Describe it’s mode of action
A

“Amphoterrible”

  1. Polyene macrolide
  2. Poorly absorbed from GIT therefore need to give IV

Amphiphile – friend of both

  1. therefore made into either

–a colloid solution (protein bound)

–A liposomal (lipid bound) delivery system

4.

  • Binds to ergosterol in the fungal cell membrane (cholesterol is the predominant sterol in mammalian cell walls)
  • Forms a pore in the fungal cell wall (increasing its permeability)
  • Allows leakage of ions and macromolecules leading to cell death
17
Q

Antifungal Agents

Amphotericin (B)

Describe the mode of action

A
  • Binds to ergosterol in the fungal cell membrane (cholesterol is the predominant sterol in mammalian cell walls)
  • Forms a pore in the fungal cell wall (increasing its permeability)
  • Allows leakage of ions and macromolecules leading to cell death
18
Q
A
19
Q

Antifungal Agents

Amphotericin (B)

What are the main IMMEDIATE adverse effects?

A
  • Immediate (infusion) reactions (almost guaranteed)
    • Fever / chills / vomiting
    • Headache / muscle spasms / hypotension
    • Premed with anti-pyretics / anti-histamines
    • Slow infusion / reduce dose

(Gradual toxicity follows)

20
Q

Antifungal Agents

Amphotericin (B)

What are the main adverse effects associated with GRADUAL TOXICITY?

A

Gradual toxicity

  • NEPHROTOXICITY
    • May be irreversible
    • Rx with iv saline
  • Hypokalaemia
  • Abnormal LFTs
  • Anaemia / thrombocytopenia

Severe side effects therefore only in severe life-threatening cases

21
Q

Antifungal Agents

Nystatin

  1. What type of drug is it?
  2. Why is it not used systemically?
  3. What is it used topically for?
  4. What will occur if swallowed?
A
  1. Polyene macrolide. Similar to amphotericin
  2. Too toxic for systemic
  3. candida infections (Thrush)
    1. No absorption from skin or mucous membranes
  4. nausea / vomiting. MOUTHWASH. Not a solution. Spit it out.
22
Q

Synthetic Antifungal agents

Azoles

  1. Give an example
  2. What types of drugs are these?
  3. What is their mode of action?
A
  1. Fluconazole
  2. Synthetic, fungistatic agents
  3. Inhibit the fungal cytochrome P450 3A enzyme (lanosine 14α-demethylase) (Key enzyme in the synthesis of ergosterol), Depletion of ergosterol in the fungal membrane inhibits membrane-associated enzyme activity. Prevents replication and hyphae transformation.
23
Q

Fluconazole

  1. What preparations are used?
  2. What is tissue and fluid penetration like?
  3. What is T1/2?
  4. How is it excreted from the body?
  5. What is a caution?
A
  1. Well absorbed orally but also available IV
  2. Good tissue and fluid penetration
  3. T ½ = 25 hours
  4. 90% excreted in urine
  5. Caution with drug interactions (hepatic enzyme inhibition) but not as bad as other anti-fungals
24
Q

Azoles - Fluconazole

What are the main adverse effects?

A
  • Nausea
  • Headache
  • Abdominal pain

Rarely:

  • Hepatitis
  • Stevens-Johnson syndrome (Severe exfoliative skin reaction)
25
Q

Antifungals

  1. What do antifungals target?
  2. How are they generally used?
  3. When are they used systemically?
A
  1. Target ergosterol in the fungal cell membrane (cholesterol is the predominant sterol in mammalian cell walls) function or formation
  2. Generally used topically - Very toxic compounds
  3. Only use systemically when patient very unwell
26
Q

Antimicrobials - Summary

A

Need to be aware of common anti-viral / anti-fungal

Have an idea of

–How they work

–When to use them

–Potential side effects

Pharmacology (26 decks)

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