Meningitis Flashcards
1
Q
Ceph and carbapenems
Common indications
A
- Oral ceph are 2nd or 3rd line treatment options for UTI and respiratory tract infections
- IV ceph and carbapenems are reserved for the treatment of infections that are very severe or complicated, or caused by antibiotic resistant organism. Due to their broad antimicrobial spectrum they can be used for most indications
2
Q
Ceph and carbapenems
MOA
A
- Cephalosporins and carbapenems are derived from naturally occuring antimicrobials produced by fungi and bacteria
- Like penicillins, their antimicrobial effect is due to their B-lactam rings
- During bacterial cell growth, ceph and carbapenems inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls
- This weakens cell wallls, preventing them from maintaining an osmotic gradient, resulting in bacterial cell swelling, lysis and death
- Both types of antibiotic have a broad spec of action
- For ceph we have increased activity against G-ve
- Ceph and carba are more resistant to b-lactamase than penicillin due to B-lactam ring fusion to dihydrothiazine ring (ceph) or hydroxyethyl side chain (carba)
3
Q
Ceph and carbapenems
Adverse effects
A
- GI upset- nausea and diarrhoea are common
- Less frequently, antibiotic-associated colitis occurs when broad-spectrum antibiotics kill normal gut flora- allowing overgrowth of toxin producing c.diff
- This is debilitating and can be complicated by colonic perforation and death
- Hypersensitivity, including immediate and delayed reactions may occur. As ceph and carba share structure with penicllins so cross-sensitivity reactions can occur
- CNS toxicity including seizures- particularly where carbapenems are prescirbed in high dose or to patients with renal impairments
4
Q
Ceph and carbapenems
Warnings
A
- Ceph and carba should be used with caution in people at risk of c.diff infections
- Particularly those in hospital and the elderly
- The main contraindication is history of allergy to a penicillin, ceph or carba- particularly if there is anaphalaxis
- Carbapenems are cautioned in patient with epilepsy a dose reduction is required for both drug classes in renal impairment
5
Q
Ceph and carbapenems
Interactions
A
- As broad-spec antibiotics- ceph and carba can enhance the activity of warfarin due to killing of gut flora which help synthesise Vit K
- Ceph may increase nephrotoxicity of aminoglycosides
- Carba reduce plasma conc and efficacy of valproate
6
Q
Penicillins
Common indications
A
- Step infections including tonsillitis, pneumonia (in combination with a macrolide if severe), endocarditis and skin and soft tissue infections (added to fluclox if severe)
- Clostridial infection e.g. tetanus
- Meningococcal infection- for example meningitis, septicaemia
7
Q
Penicillins
MOA
A
- Penicillins inhibit the enzymes responsible for cross-linking peptidoglycan in bacterial cell walls
- This weakens cell walls, preventing them from maintaining an osmotic gradient
- Uncontrolled entry of water into bacteria cuases cell-swelling, lysis and death
- Pencillins contain B-lactam ring, which is responsible for their antimicrobial activity
- Side chain attached to the B-lactam ring can be modified to make semi-synthetic penicillins by making B-lactamase, an enzyme which breaks the B-lactam ring and prevents antimicrobial activity
- Other mechanism of resistance include limiting the intracellular concentration of penicillin (reduced bacterial permeability or increased extrusion) or changes in the target enzyme to prevent penicillin binding
8
Q
Penicillin
Adverse effects
A
- Penicillin allergy affects 1-10% of people
- This is usually presents after repeat exposure
- Less commonly, an immediate life-threatening IgE-mediated anaphylactic reaction occur with some or all of hypotension, bbronchial and laryngeal spasm/oedema and angiooedema
- Central nervous system toxicity (including covulsions and coma) can occur with high doses of penicillin or where severe renal impairment delays excretion
