Antibiotics Flashcards
How do beta-lactam antibiotics work?
They disrupt bacterial wall synthesis
What is another name for phenoxymethylpenicillin?
Pen V
What are the side effects of penicillins?
GI disturbance
- diarrhoea and vomiting
What is Pen V used for?
- Otitis media
- Sinusitis
- Group A streptococcus
- Rheumatic fever
What penicillin is prescribed for cellulitis?
Flucloxacillin
Give examples of tetracycline antibiotics
Doxycycline
Lymecycline
Oxytetracycline
How do tetracyclines work?
They block mRNA translating to stop replication of bacteria
What are the side effects of tetracyclines?
- GI disturbance
- Tooth discolouration
- Enamel hypoplasia
- Deposits in bones
- Photosensitivity
What are the contraindications for tetracyclines?
- Children under 12
- Teratogenic
- Secretes into breast milk
- Idiopathic intracranial hypertension
What counselling needs to be given when prescribing tetracycline antibiotics?
- They’re prone to chelation making them less effective so shouldn’t be taken with antacids or iron supplements
- Requires loading doses, so the initial dose is higher than the rest
Give examples of macrolide antibiotics
-Mycin ones
Azithromycin, clarithromycin, erythromycin
How do macrolide antibiotics work?
They inhibit mRNA translation to stop bacterial replication
When are macrolides commonly used?
As 2nd line in penicillin allergy
- Similar indications to penicillin’s
What are the side effects of macrolides?
Usually well tolerated
- GI disturbance
- Causes prolonged GT interval
What are the drug interactions of macrolide antibiotics?
Drygs metabolised by the CYP enzymes of the liver
Eg. Warfarin
Also increased risk of rhabdomyalysis if given with statins
Which antibiotics are known to cause C.diff infection?
4 C’s:
- Co-amoxiclav
- Clindamycin
- Cephalosporins
- Ciprofloxacin
How is C.diff infection treated?
Oral vancomycin for 10 days and hydration
Give examples of quinolone antibiotics
Ciprofloxacin, levofloxacin
How do quinolone antibiotics work?
They inhibit bacterial DNA synthesis
What is ciprofloxacin used for?
(Drops) bacterial conjunctivitis, corneal ulcers, acute otitis externa
Pseudomonas in CF, meningococcal meningitis
What are the side effects of quinolone antibiotics?
- GI disturbance
- Lowered seizure threshold
- damage to muscle tendons
- Prolonged QT interval
What are the contraindications of quinolone antibiotics?
- G6PD deficiency
- Pregnancy/ breast feeding
What is trimethoprim also known as?
Co-trimoxazole
What are the indications for trimethoprim?
- Uncomplicated UTI, an alternative to nitrofurantoin and amoxicillin
- Acute pyelonephritis
- Acute prostatitis
- Acute diverticulitis
- Treatment and prophylaxis for PCP in HIV
How does trimethoprim work?
It inhibits the enzyme dihydrofolate reductase inhibitor to reduce bacterial growth
Bacteria require folate but it can’t be external
Give examples of sulflanomides
Sulphamethooxazole
What are the side effects of folate synthesis inhibiting antibiotics?
Eg, trimethoprim and sulfonamides
- Anaphylaxis
- Drug fever
- Impair haematopoiesis resulting in pancytopenia
- Increased risk of hyperkalaemia and renal impairment
- Teratogenic in first trimester or pregnancy
What is nitrofurantoin used for?
Prophylaxis and treatment of UTI’s
How does Nitrofurantoin work?
It’s reduced into an active form in acidic urine that impairs bacterial DNA
What are the side effects of nitrofurantoin?
- Hypersensitivity reactions
- Discolouration of urine to dark yellow or brown
- Prolonged use can lead to hepatitis, pneumonitis, pulmonary fibrosis, and peripheral neuropathy
- Teratogenic in 3rd trimester
What class of antibiotic is metronidazole under?
Nitroimidazole
What is metronidazole used to treat?
- Dental abscess
- Trichomonas vaginalis
- Bacterial vaginosis
- H.pylori
- PID
- Rosacea
How does metronidazole work?
It passively diffuses through the cell wall of bacteria and it reduced into into active form causing inhibition of DNA synthesis and DNA degradation
Aerobic bacteria are not susceptible to it because they can’t reduce the drug into the active form
What are the side effects of metronidazole?
- GI disturbance
- Metallic taste
- Prolonged use can lead to optic neuritis, seizures, and peripheral neuropathy
- Bad reaction when mixed with alcohol
What is the management of cellulitis?
Class 1 (patient lacks systemic symptoms)
- Oral antibiotics in outpatients
Class2 (patient with comorbid condition that affects recovery)
- Oral/IV antibiotics in outpatients
Class 3 (limb-threatening condition and systemic symptoms)
- Hospitalisation for IV antibiotics
Class 4 (severe infection/sepsis)
- Urgent hospitalisation and multiple therapy and specialist consultation
When is ceftriaxone used?
Eg. meningitis
It crosses the blood-brain barrier
What is fusidic acid?
It’s an antibiotic
