Antibiotics Flashcards
Name 5 clinical indications for antimicrobials to be prescribed
- Periapical or periodontal disease
- Cellulitis
- Sinusitis
- Oral candidiasis
- Angular cheilitis
What is the major issue with antibiotics?
Antimicrobial resistance
What is the most commonly prescribed type of antibiotic?
Penicillins
Name 3 main types of antimicrobials
- Antibiotics
- Antifungals
- Antivirals
Name 3 β-lactam drugs which are penicillin based
- Amoxicillin
- Penicillin V
- Flucloxacillin
What are 3 possible targets for chemotherapeutic agents?
- Cell wall
- Processes of protein synthesis
- Toxicity limited to low oxygen environments
What are the 2 monomers which build a bacterial cell wall?
- N-acetylglucosamine (NAG)
2. N-acetylmuramic acid (NAMA)
What is the significance of the enzyme which binds strands of monomers together to form a bacterial cell wall?
Transpeptidase is the protein which penicillin binds to
Name 2 groups of drugs which are cell wall active agents
- β-lactams
2. Glycopeptides
Name 4 types of β-lactam drugs
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenems
Name 2 glycopeptide antibiotic drugs
- Vancomycin
2. Teicoplanin
Describe the structural properties of penicillin as a drug
- β-lactam ring found in all penicillin drugs
- Ring binds with enzyme and prevents cross linking of chains of the cell wall
- Side chains contribute to variety of drugs
- Penicillin based drugs will all have similar effects due to the β-lactam ring
Describe the ADME of penicillins
- Variable stability to gastric acids so variable oral bioavailability
- 50% protein bound and low concentration in serous fluids
- Variable half life
- Entirely excreted renally
Name 4 adverse effects of penicillin
- GI upset
- Candidiasis
- Non IgE mediated rashes
- Reproducibility of reaction amongst other penicillins
Describe a true allergic reaction to penicillin
IgE mediated hypersensitivity causing angio-oedema, anaphylaxis, urticarial rash. There is immediate onset and cross reactivity amongst all penicillins
What are 3 ways an antibiotic can become resistant to penicillin?
- Altered target site for the antimicrobial
- Alteration of the uptake or output of antimicrobial agents
- Enzymatic degradation of antimicrobial agents
Why may β-lactam drugs be combined with β-lactamase inhibitors?
β-lactamase inhibitors limit the action of β-lactamase enzymes so increase activity of an antibiotic
What is the main penicillin combined with β-lactamase inhibitor drug prescribed?
Co-Amoxiclav (amoxicillin/clavulanate)
Name a tetracycline drug
Doxycycline
What 4 reasons would doxycycline be used?
- Periodontitis
- Refractory or severe forms of oral infections
- Sinusitis in the case of penicillin allergy
- Rinsed for aphthous ulcers
Describe the ADMA of tetracyclines
- Oral drugs
- Rapidly absorbed but residual in gut
- Reduced absorption with metallic ions
- Widely distributed into tissues
- Doxycycline mainly biliary excretion (can be renal and gut)
Why is there reduced absorption if tetracyclines are taken with metallic ions?
Tetracycline will bind with calcium (etc) and reduce the amount of drug which can move into the blood stream
What is the mode of action of tetracyclines?
Biding to the 30S subunit, preventing entry of amino acetyl tRNA complexes
Describe 4 adverse effects of tetracyclines
- Staining of teeth (developing teeth)
- GI disturbance
- Candidiasis
- Photosensitivity
Name 2 macrolide drugs which are prescribed as classic alternatives to penicillin
- Erythromycin
2. Clarithromycin
Describe the ADME of macrolides
- Absorption is generally good
- Wide distribution and tissue concentrations
- Half life much longer in clarithromycin than erythromycin
- Broken down in body but a small amount excreted unchanged in urine
Why is clarithromycin absorption generally better than erythromycin?
It is given as an estolate salt
What is the mode of action of macrolides?
Binds to 50S subunit, preventing translocation of the next amino acid onto the nascent peptide chain
What are 3 adverse effects of macrolides?
- GI upset
- Acts as hepatic enzyme inhibitor, so can potentiate effects of other drugs e.g. warfarin
- Rare causes of cholestatic hepatitis
To what group of drugs does clindamycin belong?
Lincosamide group
Name 3 situations where clindamycin may be used
- Recommended for endocarditis prophylaxis if penicillin allergic
- Ludwig’s angina
- Cellulitis
Describe ADME of clindamycin
- High bioavailability, with almost complete absorption
- Widely distributed including into bone and joints
- Metabolized by liver and excreted in bile and urine
- Small amount excreted unchanged in urine
What is the mode of action of clindamycin?
Binds to 50S subunit, preventing translocation of the next amino acid onto the nascent peptide chain
Name 4 adverse affects of clindamycin
- Diarrhoea
- Pseudomembranous colitis
- Nausea
- Rare cases of exfoliative dermatitis
Why can diarrhoea be a side effect of taking clindamycin?
Action on anaerobic bacteria
What type of drug can limit toxicity to low oxygen environments?
Nitroimidazoles
What is the name of the primary nitroimidazole prescribed in dentistry?
Metronidazole
What 4 things may metronidazole be used for?
- Pericoronitis
- ANUG
- Periodontitis
- Periapical disease
Describe the ADME of metronidazole
- Well absorbed and high oral bioavailability
- Distributed widely including into tissue spaces and abscess cavities
- Metabolized by liver
- Large quantity is secreted into the colon following upper GI absorption
What is the mode of action of metronidazole?
It is a pro-drug so in low oxygen conditions gets reduced to a metabolite toxic to DNA, causing inhibition of DNA synthesis and strand breakdown
What are 4 adverse effects of metronidazole?
- GI upset
- Nausea
- Disulfiram like effect (inhibits alcohol metabolism)
- Inhibits hepatic metabolism of warfarin
Name 4 general adverse effects from antimicrobials
- Stevens-Johnson syndrome
- Intrinsic staining
- Oral candidiasis
- Taste disturbance
What 3 groups of antimicrobials are likely to cause Stevens-Johnson syndrome?
- Antibacterial agents
- Antiretroviral agents
- Sulphonamide agents
What type of antibiotic is likely to cause intrinsic staining?
Tetracyclines
What 2 antibiotics are likely to cause taste disturbances?
- Metronidazole
2. Clarithromycin
