Pharmacology

Question 1

How do alpha-2-agonists work?

Answer 1

These act by stimulating pre-synaptic α2 receptors in the lateral reticular nucleus reducing central sympathetic outflow and in the spinal cord where they augment endogenous opioid release and modulate descending noradrenergic nociceptive pathways

Question 2

How do oxazolidinones work?

Answer 2

Eg linezolid
Inhibit 50s ribosomal subunit
Gram positive cover incl MRSA and VRE
Aw myelosuppression, thrombocytopenia, peripheral and optic neuropathy, lactic acidosis and MAOI - like effects

Question 3

How do lincosamides work?

Answer 3

Clindamycin
Acts on 50s ribosomal subunit
Used in necrotising soft tissue infections
Missed aerobic/ anaerobic infections esp in penicillin resistance
Anti- exotoxins effect so used in group a strep infections

Question 4

How do macrolides work? What are they used for?

Answer 4

Reversibly inhibit 50s ribosomal subunit, prevents ribosome moving along mRNA strand
Eg erythromycin, clarythromycin, azithromycin
Atypical cover
Strep and MSSA

Question 5

How do aminoglycosides work? What are they used for?

Answer 5

Eg gent and amikacin
Cause insertion of incorrect amino acid, producing false proteins and causing cell death.
Gram negative cover plus enterococcus and MRSA

Question 6

How do tetracyclines work?

Answer 6

Eg tetracycline - gram positive and negative cover
Oxytetracycline- used for atypicals, ricketsiae and Protozoa
Tigecycline - broad spec but not anti pseudomonal
Reversibly bind to 30s ribosomal subunit
Prevent tRNA binding with mRNA

Question 7

What is dapsone used for?

Answer 7

Leprosy
Acinomycoses
Toxoplasmosis

Question 8

What’s co- trimoxazole used for?

Answer 8

PCP
Stenotrophomonas maltophilia
Burkholderia cephacia

Question 9

How does trimethoprim work?

Answer 9

Inhibits conversion of dihydrofolate to tetrahydrofolate by blocking DHF reductase
THF is an co- enzyme required for the synthesis of DNA and RNA

Used for uncomplicated UTId

Question 10

Which antibiotics inhibit THF synthesis?

Answer 10

Trimethoprim
Sulphonamides eg co- trimoxazole
Dapsone

Question 11

How does ciprofloxacin work/ what’s it used for?

Answer 11

Inhibits DNA gyrase and topoisomerase-4 ( DNA synthesis)

Active against Gram negatives, atypicals and some streptococci

Question 12

How does rifampicin work/ what’s it used for?

Answer 12

Inhibits DNA dependent RNA polymerase
Anti- staphylococcal activity incl MRSA and anti- streptococcal activity
TB and leprosy
Post exposure prophylaxis in neisseria/ haemophilus meningitis

Question 13

How do nitroimidazoles work?

Answer 13

Eg metronidazole
Inhibit DNA synthesis - form complexes with DNA and cause strand breakage
Activity against anaerobes and Protozoa

Question 14

What is colistin used for?

Answer 14

Binds to LPS in cell wall of Gram negative organisms

Used for acinetobacter and pseudomonas esp in CF

Question 15

What cover do glycopeptides have?

Answer 15

Vanc is highly polar and not absorbed from GIT - used in c.diff
Vanc has poor chest penetration ( teicoplanin better)
Aerobic and anaerobic gram positive cover incl MRSA

Question 16

What is the spectrum of activity of 3rd generation cephalosporins?

Answer 16

Improved Gram negative, reduced gram positive
CNS penetration
Ceftazidime has pseudomonal cover

Eg ceftriaxome, cefotaxime

Question 17

What is the spectrum of activity of 2nd gen cephalosporins?

Answer 17

Some Gram negative cover eg e.coli, klebsiella

Eg cefuroxime

Question 18

What is the spectrum of activity of 1st generation cephalosporins?

Answer 18

Eg cephalexin

Gram positive cover

Question 19

How do cephalosporins work?

Answer 19

Beta-lactam ring as per penicillin

Question 20

Describe the spectrum of activity of carbapenems

Answer 20

Eg meropenem
Beta- lactamase resistant
Increased Gram negative and anaerobes
May be combined with another drug for improved Gram positive cover
Can be used for ESBL
Emerging resistance of enterococcus (CRE)
No activity against MRSA, atypicals or stenotrophomonas

Question 21

Describe the spectrum of activity for tazocin

Answer 21

Gram positive
Gram negative
Pseudomonas
First line for HAP/VAP/ neutropenic sepsis

Question 22

Describe the spectrum of activity for amoxicillin/ augmentin

Answer 22

Improved Gram negative cover
First line for CAP
Clavulanic acid prevents the action of beta- lactamase

Question 23

What is penicillin active against?

Answer 23

Streptococci
Enterococcus
Neisseria
Spirochetes

Question 24

How do penicillins work?

Answer 24

Transpeptidase inhibition ( enzyme that forms cross links in cell wall)
Beta lactam ring confers anti- transpeptidase activity. Beta-lactamase - producing organisms are penicillin resistant.

Question 25

What chemotherapy drugs do you know and what are their common side effects?

Answer 25

1. Alkylating agents e.g. Cyclophosphamide. Causes DNA cross links preventing replication. Causes idiopathic interstitial pneumonitis, haemorrhagic cystitis
2. Anti-metabolites e.g. methotrexate, 5-FU. Diverse mechanism - may interfere with nucleotide metabolism and therefore DNA synthesis and repair. Cause pulmonary fibrosis, nephrotoxicity, cardiotoxicity and acute cerebellar syndrome
3. Antibiotics/topoisomerase interactive agents e.g. doxorubicin and bleomycin. Interact with topoisomerase enzymes causing DNA damage. Cause cause cardiotoxicity, pulmonary fibrosis - exposure to high FiO2 causes rapid progression to fibrosis
4. Anti-microtubule agents e.g. Paclitaxel and vincristine. Interfere with mitotic and non-mitotic processed. Cause pulmonary and cardiotoxicity and peripheral neuropathy