Drug Interactions

Question 1

Common CYP inhibitors involved in drug interactions (7)

Answer 1

G<3PACMAN
Grapefruit
Protease inhibitors (esp. ritonavir)
Azole antifungals (fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole, isavuconazonium)
Cyclosporine, cobicistat
Macrolides (clarithromycin and erythromycin, NOT azithromycin)
Amiodarone (and dronedarone)
Non-DHP CCBs (diltiazem and verapamil)

Question 2

Common CYP inducers involved in drug interactions (7)

Answer 2

PS PORCS
Phenytoin
Smoking
Phenobarbital
Oxcarbazepine
Rifampin (and rifabutin, rifapentine)
Carbamazepine (also an auto-inducer)
St. John’s wort

Question 3

Common P-gp substrates

Answer 3

Anticoagulants (apixaban, edoxaban, dabigatran, rivaroxaban)
Cardiovascular drugs (digoxin, diltiazem, carvedilol, ranolazine, verapamil)
HCV drugs (sofosbuvir)
Immunosuppressants (cyclosporine, sirolimus, tacrolimus)
Others: Atazanavir, colchicine, dolutegravir, posaconazole, raltegravir, saxagliptin)

Question 4

Common P-gp inducers

Answer 4

Carbamazepine, dexamethasone, phenobarbital, phenytoin, rifampin, St. John’s wort, tipranavir

Question 5

Common P-gp inhibitors (5 categories)

Answer 5

Anti-infectives (clarithromycin, itraconazole, posaconazole)
Cardiovascular drugs (amiodarone, carvedilol, conivaptan, diltiazem, dronedarone, quinidine, verapamil)
HCV drugs (Iedipasvir)
HIV drugs (cobicistat, ritonavir)
Others (cyclosporine, flibanserin, ticagrelor)

Question 6

Drugs with additive serotonergic toxicity risk (6 categories)

Answer 6

Antidepressants (SSRIs, SNRIs, TCAs, mirtazapine, trazodone)
MAOIs (Antidepressants: Isocarboxazid, phenelzine, tranylcycpromine. Selective MAO-B inhibitors: selegiline, rasagiline. Others: linezolid, methylene blue)
Opioids: Fentanyl, meperidine, methadone, tramadol, tapentadol
Triptans: Occasional (PRN) triptan use may be safe, more frequent use can increase risk
Natural products: St. John’s wort, L-tryptophan
Others: Buspirone, lithium, dextromethorphan (when used as a drug of abuse)