OTC Interactionsss

Question 1

Cetirizine

Answer 1

All anti histamine medication and MAOIs

Significantly increases antimuscarinics S/E

Question 2

Loratadine 10mg

Answer 2

ALL antihistamines, other antimuscarinics

Increases antimuscarinics side effects

Question 3

Chlorphenamine 4mg

Answer 3

Antidepressants, anxiolytics- benzos and hypnotism opioid analgesics, alcohol

Increased CNS depression

Question 4

Fexofenadine 120mg

Answer 4

Apple and orange juice

Decreases exposure to fexofenadine

Question 5

Pseudoephedrine/Phenylepherine,Xylometazoline, Oxymetazoline

Answer 5

MAOI

Hypertensive crisis, avoid decongestants for at least 2 weeks after stopping MAOIs

Question 6

Dextromorphan

Answer 6

Antidepressants, Anxiolytics - benzos and hypnotics, opioids, alcohol, Z drugs

Increased CNS Depression

Question 7

Chloramphemicol

Answer 7

Sulphonylureas - Enhances effect of S

Tacrolimus- Enhances conc of T

Warfarin - moderate - Potentially increases anticoagulant effect

Question 8

Paracetamol

Answer 8

Alcohol - heavy drinking - increased liver damage
Flucloxacillin - High anion gap metabolic caution
Warfarin - moderate effect, Phenadione - severe effect = Increases INR

Question 9

Ibuprofen

Answer 9

Ace/ARB - Hyperkalaemia and renal damage
SSRI/SNRI- Hyperkalemia and renal damage
Baclofen, methotrexate, lithium - reduced excretion of these drugs so increases toxicity

Quinolones - Increased seizures
Thiazides - Increased nephrotoxicity

Question 10

Co codamolllll

Answer 10

Antidepressants, anxiolytics, hypnotics, opioid analgesics, alcohol,z drugs - Increased CNS depression

Clozapine - Intestinal Obstruction
MAOi - Possible CNS excitation or depression - hypertension or hypotension

Question 11

Sumatriptan

Answer 11

MAOI- Risk of CNS toxicity when MAOIs given with sumatriptan - avoid sumatriptan for 2 weeks after MAOIs

Serotonin syndrome - Low/moderate risk

Ergotamine - Vasocnstriction - don’t use with 24hrs of E

SSRI, Tapentadol - Serotonin syndrome

Question 12

Anti- emetic MIGRANES

Answer 12

Prochlorperazine - Antidepressants, anxiolytics, hypnotics, alcohol, z drugs = Increased risk of CNS depression

Anti- hypertensives/phosphodisterase type 5 inhibitors - Can increase hypotension risk

Lithium - Neurotoxicity

Question 13

Anti- emetics Travel sick

Answer 13

Cinnarizine, Promethaizne, Hyoscine - Antidepressants, anxiolytics, opioids, alcohol, z drugs

Hyoscine - all the above + TCAs and neuroleptics

= Increased antimuscarinics side effects

ALL increase CNS depression

Question 14

Mebendazole

Answer 14

Cimetidine = Increased mebendazole concentrartion

Question 15

Cystitis treatment - Potassium Citrate

Answer 15

Arb/ace, potassium sparring diuretics, spirnolactone or potassium supplements

Causes hyper kalameia

Question 16

EHCCCCCC

Answer 16

Levonorgestrel and Ella one = Carbamazepine, Fosphenytoin,oxcarbazepine, phenobarbital, St John’s wart, rifampicin , Rifabutin

Decreased clinical efficacy of EHC

Question 17

Fluconazole

Answer 17

• Anticoagulants - INR increased
  Citalopram, escitalopram , amiodarone, lithium, Macrolides, antipsychotics, methadone, quinolones, ondansetron = QT prolongation - Torsades De pointes
• Thiazide an loop diuretics - causes HYPOOOOO - torsade de pointes

Clopidogrel - cyp3a4 which reduces anti platelet effect
Ciclosporin, rifampicin, phenytoin, tacrolimus - increases plasma conc

Question 19

Clotrimazole Pessary

Answer 19

No drug interactions but can impact condoms and diaphragm - Damage = decreases contraceptive effectiveness

Question 20

Period Treatment - Hyoscine Butylbromide = 10mg

Answer 20

Cloazapine- severe increase risk of intestinal obstruction

TCAs, antihistamines, antipsychotics = increased antimuscarinics side effects

Question 21

Naproxen 250mg

Answer 21

Ace/ARB - Hyperkalaemia and renal damage and renal damage
SSRI/SNRI, anticoagulant - antiplatelets, steroids - increased bleeding

Baclofen/methotrexate/lithium = Reduce the excretion of these drugs - increased risk of toxicity

Quinolones - Increased risk of seizures
Thiazides - Increased risk of nephrotoxicity

Question 22

Heavy periods - Tranexamic acid

Answer 22

Combined oral contraceptives, cytotoxic medicines, Tamoxifen = Increased risk of thrombotic events

Question 23

Dyspepsia Treatment - Omeprazole and esoemprazole

Answer 23

Clopidogrel/ Citalopram and ecitalopram = Reduced antiplatelet effect and increased exposure of Citalopram and ecitalopram

Question 24

ALL PPIS

Answer 24

Methotrexate - reduces clearance - increased risk of toxicity

Some protease inhibitors - PPi decrease the exposure to Atazanavir - Tipranavir decreases exposure to PPi

Question 28

Reclassified Meds

Answer 28

Orlistat = Antiepileptics, antiretrovirals, oral contraceptives, NTI drugs = Orlistat might affect the absorption of concurrently administered oral drugs - consider separating administration Desogestrel - CYP3A4 inducers, ulipristal acetate Enzyme inducers decrease desogestrel contraception, reducing contraceptive effectiveness Ulipristal acetate decreases efficacy of contraceptive

Question 29

Slidenafil

Answer 29

Alpha blocker - hypotensive effect Citalopram, escitalopram, amiodarone, lithium, Macrolides, antipsychotics, methadone, quinolones, ondansetron = QT prolongation- Torsades de pointes Thiazide and loop diuretics, steroids etc - Drugs cause Hypokalaemia - Torsades de pointes Clopidogrel

Question 30

Tamsulosin

Answer 30

Beta blocker/ace/arb/ccb/diuretics = Hypotensive effects - moderate Severe interaction - Phosphodiesterase 5 inhibitors = Hypotensiver effects Ketoconazole, itraconazole, fluconazole - moderate =Increases in concentration of tamsulosin