Infection Flashcards
B lactam classes
Penicillins, Cephalosporins, Carbapenems, Monobactams
Bactericidal vs bacteriostatic
Bactericidal: kills (usually by inhibiting cell wall synthesis), bacteriostatic: inhibits reproduction/growth (inhibits protein synthesis)
Penicillin MOA
Bind to Penicillin binding protein (PBP), reduces peptidoglycan layer, bactericidal
Penicillin resistance causes
B-lactamases and PBP mutations
Cephalosporin MOA
Bind to Penicillin binding protein (PBP), reduces peptidoglycan layer, bactericidal
Cephalosporin resistance causes
B-lactamases and PBP mutations
Carbapenems MOA
Bind to Penicillin binding protein (PBP), reduces peptidoglycan layer, bactericidal
Carbapenem resistance causes
B lactamases only
Monobactams MOA
Bind to Penicillin binding protein (PBP), reduces peptidoglycan layer, bactericidal
Monobactam resistance causes
B lactamases, less susceptible than other B lactams
Aminoglycoside drugs
Gentamicin, amikacin, neomycin
Aminoglycoside spectrum of activity
gram negative aerobes (and some activity against staph and mycobacteria) No activity against anaerobes of streptococci as aminoglycosides require oxygen dependant transport into cell
Aminoglycoside MOA
Bind irreversibly to bacterial ribosomes (30s), inhibiting protein sysnthesis.
Aminoglycoside resistance causes
Reduced cell wall permeability, enzymatic alteration of aminoglycoside
Aminoglycoside ADRs
Nephrotoxicity and Ototoxicity (accumulate in renal tubular epithelial cells and cochlear/vestibular hair cells, causing cell death.
Aminoglycoside warnings
neonates, elderly, renal impairment, myasthenia gravis.
Aminoglycoside interactions
Loop diuretics (inc risk of ototoxicity), Nephrotoxicity risk increased with ciclosporin, platinum chemotherapy, cephalosporins or vancomycin.
Gentamicin dosing
Based on IBW as only distrubutes in body water and not body fat
Nystatin MOA
Bind to ergosterol in fungal cells, creates a polar pore, allows ion leakage.
Imidazole antifungals
clotrimazole
Triazole antifungals
fluconazole
Imidazole and triazole MOA
Inhibit ergosterol synthesis, which impairs cell membrane synthesis
Antifungal resistance
Rare, can occur in long term use in immunocompromised patients. Mechanisms include alteration of membrane synthesis to exclude ergosterol
Antifungal ADRs
Local use - irritation
PO Fluconazole - GI upset, headache, hepatitis and hypersensitivity. Rare- severe hepatic toxicity, QT- prolongation, anaphylaxis
Antifungal warnings
Topical- none
Fluconazole, liver damage, moderate renal impairment (dose reduction required).
Antifungal Contraindications
Pregnancy
Antifungal interactions
No significant interactions for topicals.
Fluconazole inhibits CYP450, so drugs metabolised by CYP450 including carbamazepine, phenytoin, warfarin, diazepam, simvastatin, sulphonylureas. Causes QT prolongation, so other drugs that cause QT prolongation (amiodarone, antipsychotics, quinine, quinolone, macrolides and SSRIs
Aciclovir MOA
Inhibits the herpes specific DNA polymerase
Aciclovir ADRs
headache, dizziness, GI disturbances, rash.
IV use: phlebitis, acute renal failure (risk reduced by slow rate and adequate hydration)
Aciclovir warnings
Crosses placenta and enters breast milk, so caution in pregnancy and breastfeeding. Severe renal impairment. No CIs
Aciclovir interactions
None of note
Cephalosporins and Carbapenams spectrum of activity
Broad
Antibiotics increasing C diff risk the most
clindamycin, cephalosporins (in particular second‑ and third‑generation cephalosporins), quinolones, co‑amoxiclav and aminopenicillins (for example, ampicillin and amoxicillin, which may be related to their volume of use rather than being ‘high risk’)
Carbapenems warnings
Epilsepsy (lowers seizure threshold). CI in anaphylaxis to B lactams.
Carbapenem and cephalosporin interactions
Warfarin: increases INR by killing gut bacteria that produce vitamin K.
May increase aminoglycoside nephrotoxicity
Chloramphenicol uses
Bacterial conjunctivitis, otitis externa. Occasional use Po or IV, but only in very exceptional and life threatening situations.
Chloramphenicol activity
Broad against gram pos and neg, aerobes and anaerobes.
Chloraphenicol MOA
Binds to bacterial ribosomes, inhibits protein synthesis (bacteriostatic).
Chloramphenicol resistance
acetyltransferase enzymes that directly inactivate the drug. Target modification, decreased membrane permeability and increased efflux pumps
Chloramphenicol ADRs
Topical: stinging, burning, itching.
Systemic: Bone marrow toxicity - 1. dose related (more common in high doses or in accumulation due to hepatic impairment) occurs on treatment and reversed on withdrawal. 2. Aplastic anaemia - idiosynchratic, unpredictable, may occur a while after starting. Rare but life threatening.
Gray baby syndrome- circulatory collapse in exposed neonates. Optic and peripheral neuritis may occur with prolonged use
Chloramphenicol warnings
CI: hypersensitivity reactions, bone marrow disorders, systemic CIs include third trimester, breastfeeding and children under 2. Topical use should also be avoided where possible.
Hepatic impairment
OTC chlorpamphenicol red flags
Loss of/disturbance of vision, contact lenses use, photophobia, unresolved after using drops.
