Zidovudine interactions

Oral azoles are associated with significant interactions, particularly due to cytochrome P-450 isoenzymes. Medications that interact with azoles include warfarin, phenytoin, theophylline, rifampin, cyclosporine, and zidovudine. For patients receiving only a few doses, these interactions do not pose a significant risk. These interactions may pose a risk for patients receiving long-term suppressive therapy for recurrent infections. 

Drugs that may interact with foscarnet include nephrotoxic drugs (eg, aminoglycosides, amphotericin B, IV pentamidine), pentamidine, and zidovudine. Foscarnet decreases serum levels of ionized calcium. Exercise particular caution when other drugs known to influence serum calcium levels are used concurrently. 

Drugs that may interact with acyclovir include hydantoins, probenecid, theophylline, valproic acid, and zidovudine. 

Drugs that may interact with stavudine include didanosine, doxorubicin, hydroxyurea, methadone, ribavirin, and zidovudine. 

Drugs that may interact include rifamycins, TMP-SMZ, and zidovudine. 

WARNING Renal impair is the major tox foUow administration instructions Uses CMV retinitis w/ HIV Action Selective inhibition of viral DNA synth Dose Rx 5 mg/kg IV over 1 h once/wk for 2 wk w/ probenecid Maint 5 mg/kg IV once/2 wk w/ probenecid (2 g PO 3 h prior to cidofovir, then 1 g PO at 2 h 8 h after cidofovir) X in renal impair Caution [C, -] Contra Probenecid or sulfa allergy Disp Inj SE Renal tox, chills, fever, HA, NA /D, thrombocytopenia, neutropenia Interactions t Nephrotox W/ aminoglycosides, amphot icin B, foscar-net, IV pentamidine, NSAIDs, vancomycin t effects W/zidovudine EMS Monitor ECG for hypocalcemia (t QT int val) and hypokalemia (flattened T waves) OD May cause renal failure hydration may be effective in reducing drug levels/effects Cilostazol (Pletal) TAntiplatelet, Arterial Vasodilator/ Phosphodiesterase Inhibitor] Uses Reduce Sxs of intermittent claudication Action Phosphodiesterase in inhibitor t s cAMP in pits blood vessels, vasodilation inhibit pit aggregation Dose 100 mg PO bid, 1/2 h before or 2 h after breakfast dinner Caution [C, +/-] Contra CHE, hemostatic disorders. 

Epoetin Alfa [Erythropoietin/ EPO] (Epogen/ Procrit) [Recombinant Human Erythropoietin] WARNING Use lowest dose possible may be associated w/1 CV, thromboembolic events /or mortality D/C if Hgb >12 g/dL Uses CRF associated anemia zidovudine Rx in HIV-infected pts, CA chemo -1- transfusions associated w/ surgery Action Induces ery-thropoiesis Dose Adul Peds. 50-150 Units/kg IV/SQ 3x/wk adjust dose q4-6wk PRN Surgery 300 Units/kg/d x 10 d before to 4 d after -I dose if Hct 36% or Hgb, T > 12 g/dL or Hgb t >1 g/dL in 2-wk pmod hold dose if Hgb >12 g/dL Caution [C, +] Contra Uncontrolled HTN Disp Inj SE HTN, HA, fatigue, fever, tach, NA Interactions None noted EMS Monitor ECG for hypokalemia (peaked T waves) t risk of CV thrombotic events OD May cause HA, dizziness, SOB and polycythemia symptomatic and supportive... 

Caution [B (D if near term), M] Contra Sulfonamide or salicylate sensitivity, porphyria, GI/GU obst avoid in hepatic impair Disp Tabs SE GI upset discolors urine dizziness, HA, photosens, oligospermia, anemias, Stevens-Johnson synd Interactions T Effects OF oral anticoagulants, oral hypoglycemics, MTX, pheny-toin, zidovudine X effects W/ antibiotics X effects OF digoxin, folic acid, Fe, procaine, proparacaine, sulfonylureas, tetracaine EMS T Effects of anticoagulants monitor EGG and BP for signs of hypovolemia and electrolyte disturbances d/t D skin urine may become yellow-orange may stain contact lenses T risk of photosensitivity Rxns OD May cause NA, drowsiness, HA, abd pain, skin Rxns, lactic acidosis, and jaundice symptomatic and supportive... 

The last potential mechanism to be discussed in this chapter is drug-induced altered receptor expression. Hematopoiesis is a very intricate process that is regulated by cytokines and cell-cell interactions. Interruption with any of these processes can result in hematotoxicity. For example, zidovudine (AZT) decreases Epo [27], GM-CSFaand to lesser extent IL-3 receptor expression [7]. Decrease in the expression of the above receptors seems to lead to anemia and neutropenia, by decreasing the number of CFU-E and CFU-GM, respectively. 

A fatal interaction between ritonavir and MDMA (methylenedioxymethamphetamine, ecstasy) has been reported in an HIV-positive man (see Henry et ah, 1998). The patient had allegedly taken MDMA on several occasions without untoward effects. However, several weeks after ritonavir was added to his regular medication with zidovudine and lamivudine, he took some MDMA for recreational purposes and died of a cardiorespiratory arrest within hours. Toxicology showed that the plasma MDMA concentration was about ten times that expected from the ingested dose. Inhibition of CYP2D6, the principal pathway for MDMA metabolism, by ritonavir was thought to be the most likely cause. 

Ganciclovir interacts with a number of medications, some of which are used to treat HIV or transplant patients. Ganciclovir may cause severe neutropenia when used in combination with zidovudine. Ganciclovir increases serum levels of didanosine, whereas probenecid decreases ganciclovir elimination. Nephrotoxicity may result if other nephrotoxic agents (e.g., amphotericin B, cyclosporine, NSAIDs) are administered in conjunction with ganciclovir. 

Little information on the drug interactions of ribavirin is available. In vitro, ribavirin inhibits the phosphorylation reactions that are required for activation of zidovudine and stavudine. 

Stavudine possesses several clinically significant interactions with other drugs. Although hydroxyurea enhances the antiviral activity of stavudine and didanosine, combination therapy that includes stavudine and didanosine, with or without hydroxyurea, increases the risk of pancreatitis. Combinations of stavudine and didanosine should not be given to pregnant women because of the increased risk of metabolic acidosis. Zidovudine inhibits the phosphorylation of stavudine thus, this combination should be avoided. 

C. Myelotoxicity is associated with certain NRTIs such as zidovudine. Fat redistribution, drug interactions involving CYP3A4, dyslipidemia, and diabetic symptoms are all side effects common to the protease inhibitors. 

Drug Interactions According to the product label, interactions between Intron A and other drugs have not been fully evaluated. Caution should be exercised when administering Intron A therapy in combination with other potentially myelo-suppressive agents such as zidovudine. Concomitant use of alfa interferon and theophylline decreases theophylline clearance, resulting in a 100% increase in serum theophylline levels. 

Drug interactions Vitravene is not recommended for use in patients who have recently (2-4 weeks) been treated with either intravenous or intravitreal cidofovir because of the risk of exaggerated ocular inflammation. Results from in vitro tests demonstrated no inhibition of anti-CMV activity of fomivirsen by zidovudine or zalcitabine. 

Contraindications to interferon alfa therapy include hepatic decompensation, autoimmune disease, and history of cardiac arrhythmia. Caution is advised in the setting of psychiatric disease, epilepsy, thyroid disease, ischemic cardiac disease, severe renal insufficiency, and cytopenia. Alfa interferons are abortifacient in primates and should not be administered in pregnancy. Potential drug-drug interactions include increased theophylline levels and increased methadone levels. Co-administration with didanosine is not recommended because of a risk of hepatic failure, and co-administration with zidovudine may exacerbate cytopenias. 

Drug Interactions Zidovudine Probenecid Imipenem-cilastatin Dapsone Pentamidine Flucytosine Vincristine Vinblastine Adriamycin Amphotericin B TMP-SMX Other nucleoside analogues... 

Drug Interactions Antineoplastlc agents Corticosteroids and corticotropin Cyclosporine-A Digitalis glycosides Flucytosine Imidazoles Leukocyte transfusions Nephrotoxic medications Skeletal muscle relaxants Zidovudine... 

Uses Herpes simplex zoster Tnfxns Action Interferes w/ viral DNA synth Dose Adults. Dose on IBW if obese >125% IBW PO Initial genital herpes 200 mg PO q4h while awake, 5 caps/d x 10 d or 400 mg PO dd x 7-10 d Chronic suppression 400 mg PO bid Intermittent Rx As inidal Rx, except Rx for 5 d, or 800 mg PO bid, at prodrome Herpes zoster 800 mg PO 5x/d for 7—10 d IV 5—lOmg/kg/dose IV q8h Topical Initial herpes genitalis Apply q3h (6x/d) for 7 d Peds. 5-10 mg/kg/dose IV or PO q8h or 750 mg/m2/24 h + q8h Chickenpox 20 mg/kg/dose PO qid w/ CrCl <50 mL/min Caution [B, +] Contra Hypersensitivity to compound Disp Caps, tabs, susp, inj, oint SE Dizziness, lethargy, confusion, rash, inflammation at IV site Interactions T CNS SE W/ MTX zidovudine, T blood levels H7 probenecid EMS Can cause Szs OD Causes nephrotox which can progress to ARF use fluids w/ caution, symptomatic and supportive... 

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