11.1 Antimicrobials Flashcards

Question

What must be considered before presribingcephalosporins in secondary care?

Answer 1

Individual sensitivity testing

Answer 2

``` Septicaemia Pneumonia Meningitis Biliary tract infections UTIs (especially in pregnancy or in patients unresponsive to other drugs) Sinusitis ```

Answer 3

``` Tetracyclines Aminoglycosides Macrolides Oxazolidinones Lincosamides Nitrofurans ```

Answer 4

Following uptake into susceptible organisms by active transport, tetracyclines act by inhibiting protein synthesis Bind to bacterial ribosomes, preventing binding of tRNA to it, thus preventing the initiation of protein synthesis Bacteriostatic

Answer 5

Doxycycline | Tetracycline

Answer 6

Respiratory tract infections (particularly atypical organisms) Acne Chlamydia Lyme disease

Answer 7

As causes staining of developing teeth

Answer 8

Inhibit bacterial protein synthesis by an effect on ribosomal translocation Bactericidal/bacteriostatic

Answer 9

Erythromycin Clarithromycin Azithromycin

Answer 10

The antimicrobial spectrum of macrolides is very similar to that of penicillin Also active against atypical respiratory pathogens

Answer 11

Nitrofurantoin

Answer 12

Works by being reduced to multiple reactive intermediates by nitrofuran reductase inside the bacterial cell These intermediates then attack ribosomal and DNA proteins within the bacteria, as well as inhibit the Citric acid cycle

Answer 13

Up to 50% of an oral dose Nitrofurantoin is excreted in the urine in unchanged form This allows Nitrofurantoin to concentrate within urine, leading to more effective levels within the bladder than in other tissue compartments

Answer 14

Inhibit topoisomerase II (a bacterial DNA gyrase), the enzyme that produces a negative supercoil in DNA and thus permits transcription or replication

Answer 15

Ciprofloxacin | Levofloxacin

Answer 16

``` Very good cover of Gram negative organisms, as well as atypical organisms and Gram positives Clinical applications: Complicated UTIs Pseudomonas aeruginosa cover Gonorrhoea ```

Answer 17

Tendinitis +/- rupture Aortic dissection Central nervous system effects (inc. Convulsions)

Answer 18

Folate antagonist: Reversible inhibitor of dihydrofolate reductase, which is responsible for the production of Tetrahydrofolic acid necessary for the biosynthesis of bacterial nucleic acids and proteins Binds with a much stronger affinity to bacterial dihydrofolate reductase than human Bacteriostatic/bactericidal

Answer 19

In pregnancy, has tetragenic effects on fetus

Answer 20

Protozoa and anaerobic bacteria

Answer 21

Has disulfiram-like action, advise patients to avoid using alcohol when on the antibiotic as would get severe hangover.

Answer 22

Aciclovir (DNA Polymerase Inhibitors) | Oseltamivir (Neuraminidase Inhibitors)

Answer 23

Activated predominantly in infected cells as it is phosphorylated and activated by viral enzyme thymidine. When active, acyclovir inhibits the viral DNA polymerase.

Answer 24

``` Herpes simplex infections (genital herpes, encephalitis) Varicella zoster (chicken pox, shingles) ```

Answer 25

Predominantly to treat serotype HSV-2 (genital infections. Not used to treat HSV-1/ herpes labialis in healthy patients. May be used prescribed orally in HSV-1 depending on severity, frequency and persistence of the lesions, and if the patients are immunocompromised

Answer 26

First episode: Oral Aciclovir within 5 days of the start of the episode or while new lesions are forming Recurrent episodes: Episodic antiviral treatment – if attacks are infrequent (<6/year) Either 800mg TDS for 2 days or 200mg 5x/day for 5 days. Consider self-initiated treatment, to allow for early start Suppressive antiviral treatment – if attacks are more frequent (≥6/year) OR causing psychological distress OR affecting the person’s social life 400mg BD OR 200mg QDS. If breakthrough recurrences occur, the dosage should be increased. Continue treatment for max. 1 year, after which it should be stopped to assess recurrence

Answer 27

``` Liver Small intestine Lungs Placenta Kidneys ```

Answer 28

CYP3A4 | CYP2DP

Answer 29

Warfarin is an anticoagulant that is metabolised by CYP2C9 Metronidazole is a CYP2C9 inhibitor Inhibiting the enzyme will slow down warfarin metabolism and cause warfarin overdose.

Answer 30

Macrolides inhibit CYP3A4, and should not be prescribed alongside drugs that are metabolised by this enzyme such as verapamil (CCB) and simvastatin. If prescribed together would cause CCB overdose (orthostatic hypotension) and statin overdose (myopathy and rhabdomyolysis on rare occasions)

Answer 31

Begins with drug absorption across the intestine into the portal circulation, followed by uptake into the hepatocytes. Next, drug and or conjugated metabolites are secreted into the bile and returned to the intestine, where drug can be reabsorbed into the circulation

Answer 32

Oral antibiotics can eliminate gut flora and lessen the enzymes involved in the metabolism of drugs in bile. Reduce absorption rates of drugs that are absorptive due via secondary absorption in bile due to the enterohepatic circulation. For example antibiotics, NSAIDs, hormones, opiods, digoxin, warfarin.

Answer 33

Oral antibiotics can lower the rates of enterohepatic recycling and cause lower blood concentrations of oestrogen and progesterone in patients on oral contraceptives. Increases the risk of becoming pregnant. Should use additional barrier contraceptive methods whilst on antibiotics.