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Anti-HIV Drug Interactions

A Guide to the Interactions Found Between Anti-HIV Drugs and Common HIV-Related Therapies

August 2004

Interactions Table (R)

A | B-D | E-I | K-P | S-Z

Rifabutin (Mycobutin) plus ...
Amprenavir Decreases amprenavir level by 15% and increases rifabutin level by 193% in blood. Requires lower rifabutin dose.
Anticoagulants Should be used together with caution. May decrease effectiveness of anticoagulants. Check INR.
Atovaquone Should be used together with caution. Decreases atovaquone level by 50% in blood.
AZT May decrease AZT level in blood.
Barbiturates May decrease effectiveness of barbiturates.
Beta-blockers May decrease the effectiveness of beta-blockers. Check response to treatment and adjust dose accordingly.
Buspirone May decrease effectiveness of buspirone. Check symptoms and adjust dose accordingly.
Clarithromycin Use together with caution. May increase rifabutin level and decrease clarithromycin level in blood.
Clofibrate May decrease effectiveness of clofibrate. Check response to treatment and adjust dose accordingly.
Chloramphenicol May decrease the effectiveness of chloramphenicol. Check response to treatment and adjust dose accordingly.
Corticosteroids May significantly decrease corticosteroid level in blood and require higher doses of corticosteroids.
Cyclosporine May decrease cyclosporine level in blood. Check cyclosporine blood level and adjust dose accordingly.
Dapsone Should be used together with caution. May decrease dapsone level in blood.
Delavirdine Should not be used together*. Significantly decreases delavirdine level and increases rifabutin level in blood.
Diazepam May decrease effectiveness of diazepam. Check response to treatment and adjust dose accordingly.
Digoxin Should be used together with caution. May significantly decrease effectiveness of digoxin. Check digoxin level in blood, control of heart rhythm and other cardiac symptoms.
Disopyramide May decrease effectiveness of disopyramide. Check response to treatment and adjust dose accordingly.
Doxycycline May decrease effectiveness of doxycycline. Check response to treatment and adjust dose accordingly.
Efavirenz Decreases rifabutin level in blood. Increase rifabutin dose by 50% if taken daily or double the dose if taken 3 times a week.
Estrogen Should be used together with caution. May decrease effectiveness of estrogen.
Ethinyl estradiol Should not be used together. May decrease ethinyl estradiol level in blood. Use another form of contraception.
Ethionamide Ethionamide may increase risk of side effects from other anti-TB drugs like rifabutin.
Fluconazole Should be used together with caution. May increase rifabutin level by up to 80% in blood. Increases risk of painful eye inflammation.
Fosamprenavir Should be used together with great caution. Increases risk of neutropenia. Check for side effects and lower rifabutin dose by at least 50% if fosamprenavir used alone or by 75% if boosted with ritonavir.
Glipizide Should be used together with caution. May decrease glipizide level in blood. Check blood sugar level and adjust dose accordingly.
Glyburide Should be used together with caution. May decrease glyburide level in blood. Check blood sugar level and adjust dose accordingly.
Indinavir Increases rifabutin level by 204% and decreases indinavir level by 32% in blood. Reduce rifabutin dose by half the standard dose and increase indinavir dose to 1,000 mg 3 times a day.
Itraconazole Should not be used together. May increase rifabutin level and may decrease itraconazole level in blood.
Kaletra Increases rifabutin level by 5.7-fold in blood. Rifabutin dose should be changed to 150 mg every other day or 3 times a week. Check for rifabutin side effects.
Ketoconazole Should be used together with caution. May decrease ketoconazole level in blood.
Methadone May decrease effectiveness of methadone. Check for methadone withdrawal symptoms and adjust methadone dose accordingly.
Mexiletine May decrease effectiveness of mexiletine. May require lower rifabutin dose.
Midazolam Should not be used together. Significantly decreases midazolam level in blood. Use alternative to midazolam.
Nelfinavir Should be used together with caution. Increases rifabutin and decreases nelfinavir levels in blood. Reduce rifabutin dose by one-half and use nelfinavir at 1,250 mg twice a day.
Nevirapine Should be used together with caution. May significantly affect rifabutin level in blood.
Norethindrone Should not be used together. May decrease norethindrone level in blood. Use another form of contraception.
Opiates May decrease effectiveness of opiate drugs. Check pain control and response to treatment and adjust dose accordingly.
Phenytoin Should be used together with caution. May decrease phenytoin level in blood. Check phenytoin level in blood and seizure activity. Adjust dose accordingly.
Probenecid Should be used together with caution. May increase rifabutin level in blood and increase risk of side effects.
Progesterone Should be used together with caution. May decrease effectiveness of progesterone.
Quinidine May decrease quinidine level in blood. Check response to treatment and adjust dose accordingly.
Ritonavir Should be used together with caution. Increases rifabutin level by 4-fold in blood. Increases risk of side effects. Rifabutin dose should be reduced to no more than 300 mg once a week or 150 mg every 3 days. Further dose reduction may be necessary.
Saquinavir (Fortovase) Should be used together with great caution. Decreases saquinavir level by 43% in blood. Consider alternative to rifabutin.
Saquinavir (Invirase) Should be used together with great caution. Decreases saquinavir level by 40% in blood. Consider alternative to rifabutin.
Tolbutamide Should be used together with caution. May decrease tolbutamide level in blood. Check blood sugar level and adjust dose accordingly.
Theophylline May decrease theophylline level in blood. Check theophylline level in blood and adjust dose accordingly.
Triazolam Should not be used together. Significantly decreases triazolam level in blood. Use alternative to triazolam.
Trimetrexate Should be used with caution. May affect trimetrexate and/or rifabutin level.
Verapamil Should not be used together. May significantly decrease effectiveness of verapamil.
Zolpidem May decrease effectiveness of zolpidem. Check for response to treatment and adjust dose accordingly.

Rifampin (Rifadin) plus ...
Amprenavir Should not be used together*. Significantly decreases amprenavir level in blood.
Anticoagulants Should be used together with caution. May decrease effectiveness of anticoagulants. Check INR.
Atovaquone Should be used together with caution. Decreases atovaquone level by 50% in blood.
Atazanavir Should not be used together. Rifampin decreases level of most protease inhibitors in blood.
AZT Decreases AZT level by 47% in blood. May require higher AZT dose.
Barbiturates May decrease effectiveness of barbiturates.
Clarithromycin Use together with caution. May decrease clarithromycin blood level.
Clofibrate May decrease effectiveness of clofibrate. Check response to treatment and adjust dose accordingly.
Chloramphenicol May decrease the effectiveness of chloramphenicol. Check response to treatment and adjust dose accordingly.
Corticosteroids May significantly decrease corticosteroid level in blood and require higher doses of corticosteroids.
Cyclosporine May decrease cyclosporine level in blood. Check cyclosporine blood level and adjust dose accordingly.
Dapsone Should be used together with caution. Decreases dapsone level 7–10 times in blood.
Delavirdine Should not be used together*, otherwise significantly decreases delavirdine level in blood.
Diazepam May decrease effectiveness of diazepam. Check response to treatment and adjust dose accordingly.
Digoxin Should be used together with caution. May significantly decrease effectiveness of digoxin. Check digoxin level in blood, control of heart rhythm and other cardiac symptoms.
Disopyramide May decrease effectiveness of disopyramide. Check response to treatment and adjust dose accordingly.
Doxycycline May decrease effectiveness of doxycycline. Check response to treatment and adjust dose accordingly.
Efavirenz Decreases efavirenz level by 26% in blood. Impact of interaction is uncertain.
Estrogen Should be used together with caution. May decrease effectiveness of estrogen.
Ethinyl estradiol Should not be used together. May decrease ethinyl estradiol level in blood. Use another form of contraception.
Ethionamide May increase risk of side effects from other anti-TB drugs like rifampin.
Fluconazole Should be used together with caution. Decreases fluconazole level by 23% in blood. May require higher fluconazole dose.
Food May decrease rifampin level in blood.
Fosamprenavir Should not be used together*. May decrease anti-HIV activity of fosamprenavir.
Glipizide Should be used together with caution. May decrease glipizide level in blood. Check blood sugar level and adjust dose accordingly.
Glyburide Should be used together with caution. May decrease glyburide level in blood. Check blood sugar level and adjust dose accordingly.
Halothane Should not be used together*. May increase risk of liver toxicity.
Indinavir Should not be used together*. May increase rifampin level in blood.
Isoniazid Should be used together with caution. May increase risk of liver toxicity.
Itraconazole Should not be used together. Decreases rifampin level and may decrease itraconazole level in blood.
Ketoconazole Should not be used together*. Significantly decreases ketoconazole level in blood.
Kaletra Should not be used together. Decreases lopinavir level by 75% in blood.
Methadone May decrease effectiveness of methadone. Check for methadone withdrawal symptoms and adjust methadone dose accordingly.
Mexiletine May decrease effectiveness of mexiletine. May require lower rifabutin dose.
Midazolam Should not be used together. Significantly decreases midazolam level in blood. Use alternative to midazolam.
Nelfinavir Should not be used together*. Decreases nelfinavir level by 82% in blood.
Nevirapine Should not be used together. Decreases nevirapine level in blood.
Norethindrone Should not be used together. May decrease norethindrone level in blood. Use another form of contraception.
Opiates May decrease effectiveness of opiate drugs. Check pain control and response to treatment and adjust dose accordingly.
Phenytoin Should be used together with caution. May decrease phenytoin level in blood. Check phenytoin level in blood and seizure activity. Adjust dose accordingly.
Probenecid Should be used together with caution. May increase rifampin level in blood and increase risk of side effects.
Progesterone Should be used together with caution. May decrease effectiveness of progesterone.
Quinidine May decrease quinidine level in blood. Check response to treatment and adjust dose accordingly.
Ritonavir Should not be used together. Decreases ritonavir level by 35% in blood. Consider using rifabutin instead.
Saquinavir (Fortovase) Should not be used together. Decreases saquinavir level by 84% in blood.
Saquinavir (Invirase) Should not be used together. Decreases saquinavir level by 80% in blood.
Theophylline May decrease theophylline level in blood. Check theophylline level in blood and adjust dose accordingly.
Triazolam Should not be used together. Significantly decreases triazolam level in blood. Use alternative to triazolam.
Trimetrexate Should be used together with caution. May affect trimetrexate and/or rifampin level in blood.
Verapamil Should not be used together. May significantly decrease effectiveness of verapamil.
Zolpidem May decrease effectiveness of zolpidem. Check for response to treatment and adjust dose accordingly.

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Ritonavir (Norvir) plus ...
Alfentanil Should be used with caution. May significantly increase alfentanil level in blood. May require lower alfentanil dose.
Alprazolam Should be used together with caution. Although ritonavir decreases alprazolam level in blood, it may also prolong sedation.
Amiodarone Should not be used together*. Increases risk of side effects.
Amitriptyline Should be used together with great caution. May increase amitriptyline level in blood. May require lower amitriptyline dose.
Amlodipine Should be used together with caution. May significantly increase amlodipine level in blood. May require lower amlodipine dose.
Amoxapine Should be used together with great caution. May increase amoxapine level in blood. May require lower amoxapine dose.
Amprenavir Increases amprenavir level by 70% in blood. Alternate dosing is amprenavir 600 mg + ritonavir 100 mg twice a day, or amprenavir 1,200 mg + ritonavir 200 mg once daily.
Astemizole Should not be used together*. Increases risk of side effects.
Atazanavir Substantially increases atazanavir level in blood. If combined, use atazanavir 300 mg once a day (with food) + ritonavir 100 mg once a day.
Atorvastatin Should be used together with great caution. Ritonavir + saquinavir increases atorvastatin level by 343% in blood. Use lowest dose of atorvastatin or consider using pravastatin.
Atovaquone May decrease atovaquone level in blood.
AZT Decreases AZT level by 25% in blood. No dose adjustment recommended.
Bepridil Should not be used together*. Increases risk of side effects.
Bromocriptine Should be used together with caution. May significantly increase bromocriptine level in blood. May require lower bromocriptine dose.
Buproprion Should be used together with caution. Increases risk of side effects.
Buprenorphine Should be used with caution. May significantly increase buprenorphine level in blood. May require lower buprenorphine dose.
Butorphanol Should be used with caution. May significantly increase butorphanol level in blood. May require lower butorphanol dose.
Carbamazepine Should be used together with caution. May significantly increase carbamazepine level in blood. May require lower carbamazepine dose.
Chlorpromazine Should be used together with caution. May increase chlorpromazine level in blood. Check for side effects.
Cisapride Should not be used together*. Increases risk of side effects.
Citalopram Should be used together with caution. May increase citalopram level in blood. May require lower citalopram dose.
Clarithromycin Increases clarithromycin level by 77% and increases ritonavir level by 12% in blood. Requires lower dose of clarithromycin and checking for kidney toxicity in people with a history of kidney problems.
Clofibrate May decrease clofibrate level in blood.
Clomipramine Should be used together with caution. May increase clomipramine level in blood. May require dose reduction of clomipramine.
Clonazepam Should be used together with caution. May increase clonazepam level in blood. May require dose reduction of clonazepam.
Clorazepate Should be used together with caution. Increases risk of side effects.
Clotrimazole May increase risk of side effects.
Clozapine Should not be used together*. Increases risk of side effects.
Codeine Should be used with caution. May decrease codeine level in blood. May require lower codeine dose.
Cyclosporine May significantly increase cyclosporine level in blood.
ddI or ddI EC Decreases ddI level by 13% in blood. No dose adjustment recommended, but take 2½ hours apart.
Delavirdine Increases ritonavir level by about 51% in blood. May require lower ritonavir dose.
Desipramine Should be used together with caution. Increases desipramine level by 145% in blood. Check desipramine level in blood and adjust dose accordingly.
Dexamethasone Should be used together with caution. May significantly increase dexamethasone level in blood. May require lower dexamethasone dose.
Diazepam Should be used together with caution. Increases risk of side effects.
Dihydroergotamine Should not be used together*. Increases risk of side effects.
Diltiazem Should be used together with caution. May significantly increase diltiazem level in blood. May require lower diltiazem dose.
Diphenoxylate May decrease diphenoxylate level in blood.
Disopyramide Should be used together with caution. May increase disopyramide level in blood and increase heart (cardiac) and brain/nerve (neurological) side effects. May require lower disopyramide dose.
Divalproex Should be used together with caution. May decrease divalproex level in blood. A higher divalproex dose may be necessary.
Doxepin Should be used together with caution. May increase doxepin level in blood. May require lower doxepin dose.
Dronabinol Should be used together with caution. May increase dronabinol level in blood. May require lower dronabinol dose.
Efavirenz Should be used together with caution. Increases efavirenz level by 21% and ritonavir level by 18% in blood. Check for side effects.
Encainide Should not be used together*. Increases risk of side effects.
Enfuvirtide Ritonavir used at the full dose increases enfuvirtide level by 22% in blood. Ritonavir at a boosting dose of 100 mg twice a day increases enfuvirtide level by 14% in blood. No dose adjustment recommended.
Ergonovine Should not be used together*. Increases risk of side effects.
Ergotamine Should not be used together*. Increases risk of side effects.
Erythromycin Should be used together with caution. May increase erythromycin level in blood. May require lower erythromycin dose.
Escitalopram Should be used together with caution. May increase escitalopram level in blood. May require lower escitalopram dose.
Estazolam Should be used together with caution. Increases risk of side effects.
Ethinyl estradiol Should not be used together. Decreases ethinyl estradiol level by 40% in blood. Use another form of contraception.
Ethosuximide Should be used together with caution. May increase ethosuximide level in blood. May require lower ethosuximide dose.
Etoposide Should be used with great caution. May increase etoposide level in blood and increase risk of side effects.
Felodipine Should be used together with caution. May significantly increase felodipine level in blood. May require lower felodipine dose.
Fentanyl Should be used together with caution. May significantly increase fentanyl level in blood. May require lower fentanyl dose.
Flecainide Should not be used together*. Increases risk of side effects.
Flucitasone propionate Should not be used together. Increases risk of side effects.
Fluconazole Increases ritonavir level by 12% in blood. No dose adjustment recommended; however, check for liver toxicity.
Fluoxetine Should be used together with great caution. May increase risk of serious side effects. May require lower fluoxetine dose.
Flurazepam Should be used together with caution. Increases risk of side effects.
Fluvastatin Should be used together with caution. May increase fluvastatin level in blood. Check for toxicity.
Fluvoxamine Should be used together with caution. May increase fluvoxamine level in blood. May require lower fluvoxamine dose.
Food Increases ritonavir level in blood.
Fosamprenavir Increases fosamprenavir level in blood. Adjust dose to fosamprenavir 700 mg + ritonavir 100 mg twice a day or fosamprenavir 1,400 mg + ritonavir 200 mg once a day.
Foscarnet Should be used with caution. Abnormal kidney function has been observed.
Haloperidol Should be used together with caution. May increase haloperidol level in blood. Check for side effects.
Hydrocodone Should be used with caution. May significantly increase hydrocodone level in blood. May require lower hydrocodone dose.
Hydromorphone Should be used with caution. May significantly increase hydromorphone level in blood. May require lower hydromorphone dose.
Imipramine Should be used together with caution. May increase imipramine level in blood. May require lower imipramine dose.
Indinavir Ritonavir significantly increases indinavir level in blood. Adjust dose to indinavir 800 mg + ritonavir 200 mg twice a day or indinavir 400 mg + ritonavir 400 mg twice a day.
Isradipine Should be used together with caution. May significantly increase isradipine level in blood. May require lower isradipine dose.
Itraconazole Should be used together with caution. May significantly increase itraconazole level in blood.
Ketoconazole Should be used together with caution. Significantly increases ketoconazole level in blood. Ketoconazole dose should not exceed 200 mg/day.
Ketoprofen May increase ketoprofen level in blood.
Ketorolac May increase ketorolac level in blood.
Lamotrigine Should be used together with caution. May decrease lamotrigine level in blood. A higher lamotrigine dose may be necessary.
Lidocaine Should be used together with caution. May significantly increase lidocaine level in blood. May require lower lidocaine dose.
Loperamide Should not be used together. Decreases the effectiveness of loperamide.
Loratadine Should be used together with caution. May increase loratadine level in blood. Check for side effects.
Lorazepam May increase lorazepam level in blood.
Lovastatin Should not be used together. May significantly increase lovastatin level in blood.
Maprotiline Should be used together with caution. May increase maprotiline level in blood. Check for side effects.
Mefloquine Should be used with great caution. May significantly decrease ritonavir level in blood.
Meperidine Decreases meperidine level in blood, but leads to increased concentrations of the active metabolite normeperidine over time. Long-term use in combination at higher meperidine doses is not recommended.
Methadone Decreases methadone level by about 40% in blood. Check for methadone withdrawal symptoms and adjust methadone dose accordingly.
Methamphetamine Caution is warranted. May increase methamphetamine level in blood.
Methylergonovine Should not be used together*. Increases risk of side effects.
Metoclopramide May decrease metoclopramide level in blood.
Metoprolol Should be used together with caution. May increase metoprolol level in blood. May require lower metoprolol dose.
Metronidazole Should be used together with caution. May increase risk of side effects (ritonavir liquid only).
Mexiletine Should be used together with caution. May increase mexiletine level in blood and increase heart (cardiac) and brain/nerve (neurological) side effects. May require lower mexiletine dose.
Miconazole Should be used together with caution. May increase miconazole level in blood. Check for side effects.
Midazolam Should not be used together*. Increases risk of side effects.
Morphine Should be used together with caution. May decrease morphine level in blood. Check for pain management and possible withdrawal symptoms and adjust dose accordingly.
Naproxen May increase naproxen level in blood.
Nefazadone Should be used together with caution. May significantly increase nefazadone level in blood and increase cardiac and neurological side effects. May require dose reduction of nefazadone.
Nelfinavir Increases ritonavir level by 9% and increases nelfinavir level by 152% in blood. Other dose under study includes nelfinavir 500–750 mg + ritonavir 400 mg twice a day.
Nevirapine Decreases ritonavir level by 11% in blood. No dose adjustment recommended.
Nicardipine Should be used together with caution. May significantly increase nicardipine level in blood. May require lower nicardipine dose.
Nifedipine Should be used together with caution. May significantly increase nifedipine level in blood. May require lower nifedipine dose.
Nimodipine Should be used together with caution. May significantly increase nimodipine level in blood. May require lower nimodipine dose.
Nisoldipine Should be used together with caution. May significantly increase nisoldipine level in blood. May require lower nisoldipine dose.
Nitrendipine Should be used together with caution. May significantly increase nitrendipine level in blood. May require lower nitrendipine dose.
Nortriptyline Should be used together with caution. May increase nortriptyline level in blood. May require lower nortriptyline dose.
Ondansetron Should be used together with caution. May increase ondansetron level in blood. Check for side effects.
Oxazepam May increase oxazepam level in blood.
Oxycodone Should be used with caution. May significantly increase oxycodone level in blood. May require lower oxycodone dose.
Paclitaxel Should be used together with caution. May increase paclitaxel level in blood. Check for side effects.
Paroxetine Should be used together with caution. May increase paroxetine level in blood. May require lower paroxetine dose.
Penbutolol Should be used together with caution. May increase penbutolol level in blood. May require lower penbutolol dose.
Pentazocine Should be used with caution. May significantly increase pentazocine level in blood. May require lower pentazocine dose.
Perphenazine Should be used together with caution. May increase perphenazine level in blood. May require lower perphenazine dose.
Phenytoin Should be used together with caution. May decrease phenytoin level in blood. An increased dose of phenytoin may be necessary.
Pimozide Should not be used together*. Increases risk of side effects.
Pindolol Should be used together with caution. May increase pindolol level in blood. Check for side effects.
Piroxicam Should not be used together*. Increases risk of side effects.
Pravastatin No clinically significant interactions with ritonavir as sole protease inhibitor. However, ritonavir + saquinavir decreases pravastatin level by 47% in blood.
Prednisone Should be used together with caution. May increase prednisone level in blood. May require lower dexamethasone dose.
Propafenone Should not be used together*. Increases risk of side effects.
Propoxyphene Should be used together with caution. Increases risk of side effects.
Protriptyline Should be used together with caution. May increase protriptyline level in blood. May require lower protriptyline dose.
Quinine Should be used together with caution. May significantly increase quinine level in blood. May require lower quinine dose.
Quinidine Should not be used together*. Increases risk of side effects.
Rapamycin Should be used together with caution. May significantly increase rapamycin level in blood. May require lower rapamycin dose.
Rifabutin Should be used together with caution. Increases rifabutin level by 4-fold in blood. Increases risk of side effects. Rifabutin dose should be reduced to no more than 300 mg once a week or 150 mg every 3 days. Further dose reduction may be necessary.
Rifampin Should not be used together. Decreases ritonavir level by 35% in blood. Consider using rifabutin instead.
Risperidone Should be used together with caution. May increase risperidone level in blood. May require lower risperidone dose.
Saquinavir (Fortovase) Increases saquinavir level by 1,587% in blood. Adjust doses to saquinavir 1,000 mg + ritonavir 100 mg twice a day.
Saquinavir (Invirase) Increases saquinavir level by about 20 times in blood. Adjust doses to saquinavir 1,000 mg + ritonavir 100 mg twice a day.
Sertraline Should be used together with caution. May significantly increase sertraline level in blood. May require lower sertraline dose.
Sildenafil Should be used with caution. Increases sildenafil level by 11 times in blood. Sildenafil dose should not exceed 25 mg within a 48 hour period.
Simvastatin Should not be used together. Ritonavir + saquinavir increases simvastatin level by 3,059% in blood.
St. John's Wort Should not be used together. May significantly decrease ritonavir level in blood.
Tacrolimus Should be used together with caution. May significantly increase tacrolimus level in blood. May require lower tacrolimus dose.
Tamoxifen Should be used together with caution. May significantly increase tamoxifen level in blood. Check for side effects.
Tedalafil Should be used together with caution. Increases tedalafil level in blood. Tedalafil dose should not exceed 10 mg in a 72 hour period.
Temazepam May increase temazepam level in blood.
Theophylline Decreases theophylline level by 43% in blood. Check theophylline level in blood and adjust dose accordingly.
Thioridazine Should be used together with caution. May increase thioridazine level in blood. May require lower thioridazine dose.
Timolol Should be used together with caution. May increase timolol level in blood. May require lower timolol dose.
Tipranavir Increases tipranavir level 12 times and decreases ritonavir level by 75–80% in blood. Other doses now under study.
Tramadol Should be used together with caution. May increase tramadol level in blood. May require lower tramadol dose.
Trazodone Increases trazodone level in blood. Trazodone dose may need to be reduced.
Triazolam Should not be used together*. Increases risk of side effects.
Trimipramine Should be used together with caution. May increase trimipramine level in blood. May require lower trimipramine dose.
Vardenafil Should be used together with caution. Increases vardenafil level in blood. Vardenafil dose should not exceed 2.5 mg in a 72 hour period.
Venlafaxine Should be used together with caution. May increase venlafaxine level in blood. May require lower venlafaxine dose.
Verapamil Should be used together with caution. May significantly increase verapamil level in blood. May require lower verapamil dose.
Vinblastine Should be used together with caution. May increase vinblastine level in blood. Check for side effects.
Vincristine Should be used together with caution. May increase vincristine level in blood. Check for side effects.
Voriconazole Should not be used together. Increases risk of side effects.
Warfarin Should be used together with caution. May decrease warfarin level in blood. A higher warfarin dose may be necessary; however, closely check INR.
Zolpidem Should be used together with caution. Increases risk of side effects.


Interpreting Directions

Should not be used together
The risk of side effects from a combination is too high for the two medications to be used together.

An asterisk (*) following this phrase means the side effects may be life-threatening.

Should be used together with caution
The risk of side effects from a combination is possible, but not highly common.

Should be used together with great caution
The risk of side effects from a combination is possible, and though not common may be serious if they occur.




  
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