Pneumonia Flashcards
1
Q
Penicillin (Amoxicillin)
Common indications
A
- Antipseudomonal penicillins are reserved for severe infections, particularly where there is a broad spectrum of potential pathogens (including Pseudomonas aeruginosa); antibiotic resistance is likely (e.g. hospital-acquired infection); or patients are immunocompromised (e.g. neutropenia). Clinical infections treated with these drugs include:
- Lower respiratory tract infection
- Urinary tract infection
- Intra-abdominal sepsis.
- Skin and soft tissue infection
2
Q
Penicillin (Amoxicillin)
MOA
A
- Penicillins inhibit the enzymes responsible for cross-linking peptidoglycans in bacterial cell walls. This weakens cell walls, preventing them from maintaining an osmotic gradient. The uncontrolled entry of water into bacteria causes cell swelling, lysis and death.
- Penicillins contain a β-lactam ring, which is responsible for their antimicrobial activity. Sidechains attached to the β-lactam ring can be modified to make semi-synthetic penicillins. For piperacillin, the side chain of broad-spectrum penicillins has been converted to a form of urea
- This longer side chain may improve affinity to penicillin-binding proteins, increasing the spectrum of antimicrobial activity to include Pseudomonas aeruginosa. Addition of the β-lactamase inhibitor tazobactam confers antimicrobial activity against β-lactamase- producing bacteria (e.g. Staphylococcus aureus, Gram-negative anaerobes).
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3
Q
Penicillins (amoxicillin)
Adverse effects
A
- GI upset including N&V, diarrhoea is common
- Less frequently antibiotic-associated colitis occurs when broad-spectrum antibiotics kill normal GI flora, Allowing overgrowth of toxin-producing C.dif
- This is debilitating and can be complicated by clonic perforation and/or death
- Delayed or immediate hypersensitivity may occur
4
Q
Penicillin (amoxicillin)
Warnings
A
- At the risk of C.dif infections- particularly those in hospital and the elderly
- The main contraindication is a penicillin allergy
- Moderate to severe renal impairment
5
Q
Penicillins (amoxicillin)
Interactions
A
- MTX-increases the risk of toxicity, penicillins reduce renal excretion of MTX
- Penicillins increase the risk of bleeding with warfarin (kill bacteria that synthesis Vit K)
6
Q
Macrolides
Common indications
A
- Treatment of respiratory and skin and soft tissue infections as an alternative to penicillin when this is contraindicated by an allergy.
- In severe pneumonia added to penicillin to cover atypical organisms including Legionella pneumophila and Mycoplasma pneumonia.
- Eradication of Helicobacter pylori (for example causing peptic ulcer disease) in combination with a proton pump inhibitor and either amoxicillin or metronidazole.
7
Q
Macrolides
MOA
A
- Macrolides inhibit bacterial protein synthesis. They bind to the 50S subunit of the bacterial ribosome and block translocation, a process required for elongation of the polypeptide chain.
- Inhibition of protein synthesis is ‘bacteriostatic’ (stops bacteria growth), which assists the immune system in killing and removing bacteria from the body.
- Erythromycin, the first macrolide, was isolated from Streptomycetes erythraeus in the 1950s. It has a relatively broad spectrum of activity against Gram-positive and some Gram-negative organisms.
- Synthetic macrolides (e.g. clarithromycin and azithromycin) have increased activity against Gram-negative bacteria, particularly Haemophilus influenzae. Bacterial resistance to macrolides is common, mainly due to ribosomal mutations preventing macrolide binding
8
Q
Macrolides
Adverse effects
A
- Adverse effects are most common and severe with erythromycin, but can occur with any macrolides
- Macrolides are irritant, causing N&V, ab pain and diarrhoea when taken orally and thrombophlebitis when given IV
- Other side effects include allergy, antibiotic-associated colitis, liver abnormalities- cholestatic jaundice, prolongation of the QT interval and ototoxicity at high doses
9
Q
Macrolides
Warnings
A
- Hypersensitivity
- Severe hepatic
- Severe renal impairment
10
Q
Macrolide
Interactions
A
- Erythromycin and clarithromycin (but not azithromycin) inhibit cytochrome P450 enzymes. This increases plasma concentrations and risk of adverse effects with drugs metabolised by P450 enzyme. For example, with warfarin, there is an increased risk of bleeding and statins with myopathy
- Macrolides should be prescribed with caution in patients taking other drugs that prolong the QT interval or cause arrhythmias, such as amiodarone, antipsychotics, quinine, quinolone antibiotics and SSRIs
11
Q
Teicoplanin
Indications
A
- C.diff
- Diabetic foot infections/ leg ulcers
- Cellulitis
- Serious infections caused by G+ve bacteria (e.g. Pneumonia, UTI, skin infections)
- Streptococcal or enterococcal endocarditis
- Surgical prophylaxis
- Peritonitis (dialysis patients)
12
Q
Teicoplanin
MOA
A
- Teicoplanin inhibits the growth of susceptible organisms by interfering with cell-wall biosynthesis at a site different from that affected by beta-lactams
- Peptidoglycan synthesis is blocked by specific binding to D-alanyl-D-alanine residues
- Mechanism of resistance
- Modified D-alanyl-D-alanine- caused by D-lactate dehydrogenase/ligase
- Overproduction of murein precursors- which teicoplanin bind to
13
Q
Teicoplanin
Warnings
A
- Do not give by mouth due to poor PO absorption
- Remember the loading dose 12mg/kg BD
14
Q
Teicoplanin
Adverse effects
A
- Hypersensitivity reactions
- Ototoxicity- deafness
- Nephrotoxicity
- Skin reactions
- Elevated LFTs
15
Q
Teicoplanin
Interactions
A
- No specific interactions
