ABX: DDI

Question 1

Not with NSAID

Answer 1

1. fluoroquinolone-induced seizures

2. aminoglycoside (increase PG, block renal blood flow more, more nephrotoxic)

Question 2

warfarin (3)

DOAC

Answer 2

1. Cephalosporin
2. Cotrimoxazole (displace warfarin from albumin)
3. fluoroquinolones
4. tigecycline (increase AUC but dont affect INR)

metronidazole (hypothrombinemia)
Sulphonamide (sulfamethoxazole, sulphadiamine) (displace from albumin)

Question 3

OCP (2 drugs)

Answer 3

Penicillin

Tetracycline

Question 4

King of DDI

Answer 4

1. fluoroquinolones bc it is inhibitor and substrate
   - with theophylline,
   - with cyp substrate (cause metabolism to decrease) e.g. SIMVASTATIN, CARBAZEPINE, CYCLOSPORINE
   - w cyp inducer (rifampicin, phenytoin, phenobaritone, carbamazepine)

Question 5

DDI of tetracycline

DDI of tigecycline

Answer 5

tetra:

1. w enzyme inducer (phenytoin, carbamazepine, phenobaritone)
2. antacid/Fe/ Mg supp: chelate with cations so decrease A
3. OCP
4. Lipid lowering drug, cholestyramine
5. food (mino/doxy < tetracycline)

Tige:
warfarin (incerease AUC, but wont change INR)

Question 6

DDI of fluoroquinolones

Answer 6

1. CIprofloxacin + theophylline: higher risk of death bc cipro is potent inhibitor of CYP1A2, a main metabolising enzyme of cipro
   (other potent CYP1A2: ery/clarithromycin.)
   (so can only use levoflaxcin/oflaxacin)

Theophylline toxicity: tremours/seizures, excessive nervousness/anxiety, arrhythmias/tachy

2. CYP inducer (since its a substrate of CYP)
3. NSAID -quinolone-induced seizures
4. warfarin

Question 7

Food interaction

Answer 7

tetracycline (less for mino/doxy)

Question 8

DDI of macrolides

Answer 8

1. SIMVASTATIN,CARBAMAZEPINE,CYCLOSPORINE (ery & clari will inhibit the met CYP3A4)
2. Digoxin: ery & clari will inactivate GI bact which can met digoxin in GI, so cause digoxin-induced toxicity due to increase in digoxin conc by 2-4x
3. concomitant QT prolongation drugs

Question 9

Digoxin
theophylline toxicity
Serotonin syndrome

Answer 9

arrhythmias, alter colour vision, mental change, anorexia

arrhythmias/tachy, tremours/seizures, excessive anxeity/nervousness

More E, higher BP, mental change, NM abnormality, autonomic hyperactivity

Question 10

DDI of clindaymycin

Answer 10

nm blocking agent

Question 11

DDI of linezolid

Answer 11

1. rifampicin
2. MAOI –> serotonin syndrome
   e.g. of MAOI: SSRI
   tyramine rich (cheese/wine/chicken liver/marmite)
   Adrenergic agent (E,pseudoE,phenylE, salbutamol, terbutaline))

Question 12

DDI with food/antacid

Answer 12

tetracycline (antacid, milk, Fe, Ca)
fluoroquinolones (antacid, milk, Fe, Ca)
nitrofurantoin (anatcid only)

itraconazole: capsules take with food and coke, not with antacid/ppi