Because candesartan is not significantly metabolized by the cytochrome P450 system and at therapeutic concentrations has no effects on P450 enzymes, interactions with drugs that inhibit or are metabolized by those enzymes would not be expected.
Interactions common to both Candesartan Cilexetil and Hydrochlorothiazide
Non-Steroidal Anti-Inflammatory Agents including Selective Cyclooxygenase-2 Inhibitors (COX-2 Inhibitors)
In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, co-administration of NSAIDs, including selective COX-2 inhibitors, with angiotensin II receptor antagonists, including candesartan, may result in deterioration of renal function, including possible acute renal failure. These effects are usually reversible. Monitor renal function periodically in patients receiving candesartan and NSAID therapy.
The antihypertensive effect of angiotensin II receptor antagonists, including candesartan may be attenuated by NSAIDs including selective COX-2 inhibitors.
Increases in serum lithium concentrations and lithium toxicity have been reported during concomitant administration of lithium with angiotensin II receptor antagonists or hydrochlorothiazide. Monitor serum lithium levels during concomitant use.
Interactions with Candesartan Cilexetil
Dual Blockade of the Renin-Angiotensin System (RAS)
Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy. Closely monitor blood pressure, renal function and electrolytes in patients on candesartan cilexetil and hydrochlorothiazide tablets and other agents that affect the RAS.
Co-administration of candesartan cilexetil and hydrochlorothiazide tablets with potassium sparing diuretics, potassium supplements, potassium-containing salt substitutes or other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients.
Do not co-administer aliskiren with candesartan cilexetil and hydrochlorothiazide tablets in patients with diabetes. Avoid use of aliskiren with candesartan cilexetil and hydrochlorothiazide tablets in patients with renal impairment (GFR <60 mL/min) (see CONTRAINDICATIONS).
Interactions with Hydrochlorothiazide
Alcohol, barbiturates, or narcotics − Potentiation of orthostatic hypotension may occur.
Antidiabetic drugs (oral agents and insulin) − Dosage adjustment of the antidiabetic drug may be required.
Diazoxide − the hyperglycemic effect of diazoxide may be enhanced by thiazides.
Ion Exchange resins − Single doses of either cholestyramine or colestipol resins bind the hydrochlorothiazide and reduce its absorption from the gastrointestinal tract by up to 85% and 43%, respectively. Stagger the dosage of hydrochlorothiazide and ion exchange resins such that hydrochlorothiazide is administered at least 4 hours before or 4-6 hours after the administration of resins.
Skeletal muscle relaxants, nondepolarizing (e.g., tubocurarine) − Possible increased responsiveness to muscle relaxants such as curare derivatives.
Digitalis − Thiazide-induced hypokalemia or hypomagnesemia may predispose to digoxin toxicity.
Noradrenaline – Thiazides may decrease arterial responsiveness to noradrenaline, but not enough to preclude effectiveness of the pressor agent for therapeutic use.
Steroids or Adrenocorticotropic Hormone – Hypokalemia may develop during concomitant use of steroids or adrenocorticotropic hormone (ACTH).
Cytotoxic products – Thiazides may reduce the renal excretion of cytotoxic medicinal products (e.g. cyclophosphamide, methotrexate) and potentiate their myelosuppressive effects.
Cyclosporine − Concomitant treatment with cyclosporine may increase the risk of hyperuricemia and gout-type complications.
No carcinogenicity studies have been conducted with the combination of candesartan cilexetil and hydrochlorothiazide. There was no evidence of carcinogenicity when candesartan cilexetil was orally administered to mice and rats for up to 104 weeks at doses up to 100 and 1000 mg/kg/day, respectively. Rats received the drug by gavage whereas mice received the drug by dietary administration. These (maximally-tolerated) doses of candesartan cilexetil provided systemic exposures to candesartan (AUCs) that were, in mice, approximately 7 times and, in rats, more than 70 times the exposure in man at the maximum recommended daily human dose (32 mg). Two-year feeding studies in mice and rats conducted under the auspices of the National Toxicology Program (NTP) uncovered no evidence of a carcinogenic potential of hydrochlorothiazide in female mice (at doses of up to approximately 600 mg/kg/day) or in male and female rats (at doses of up to approximately 100 mg/kg/day). The NTP, however, found equivocal evidence for hepatocarcinogenicity in male mice.
Candesartan cilexetil or candesartan (the active metabolite), in combination with hydrochlorothiazide, tested positive in vitro in the Chinese hamster lung (CHL) chromosomal aberration assay and mouse lymphoma mutagenicity assay. The candesartan cilexetil/hydrochlorothiazide combination tested negative for mutagenicity in bacteria (Ames test), for unscheduled DNA synthesis in rat liver, for chromosomal aberrations in rat bone marrow and for micronuclei in mouse bone marrow.
Both candesartan and its O-deethyl metabolite tested positive for genotoxicity in the in vitro CHL chromosomal aberration assay. Neither compound tested positive in the Ames microbial mutagenesis assay or in the in vitro mouse lymphoma cell assay. Candesartan (but not its O-deethyl metabolite) was also evaluated in vivo in the mouse micronucleus test and in vitro in the Chinese hamster ovary (CHO) gene mutation assay, in both cases with negative results. Candesartan cilexetil was evaluated in the Ames test, the in vitro mouse lymphoma cell assay, the in vivo rat hepatocyte unscheduled DNA synthesis assay and the in vivo mouse micronucleus test, in each case with negative results. Candesartan cilexetil was not evaluated in the CHL chromosomal aberration or CHO gene mutation assays.
When hydrochlorothiazide was tested alone, positive results were obtained in vitro in the CHO sister chromatid exchange (clastogenicity) and mouse lymphoma cell (mutagenicity) assays and in the Aspergillus nidulans non-disjunction assay. Hydrochlorothiazide was not genotoxic in vitro in the Ames test for point mutations and the CHO test for chromosomal aberrations, or in vivo in assays using mouse germinal cell chromosomes, Chinese hamster bone marrow chromosomes, and the Drosophila sex-linked recessive lethal trait gene.
No fertility studies have been conducted with the combination of candesartan cilexetil and hydrochlorothiazide. Fertility and reproductive performance were not affected in studies with male and female rats given oral doses of up to 300 mg candesartan cilexetil/kg/day (83 times the maximum daily human dose of 32 mg on a body surface area basis). Hydrochlorothiazide had no adverse effects on the fertility of mice and rats of either sex in studies wherein these species were exposed, via their diet, to doses of up to 100 and 4 mg/kg, respectively, prior to conception and throughout gestation.
It is not known whether candesartan is excreted in human milk, but candesartan has been shown to be present in rat milk. Thiazides appear in human milk. Because of the potential for adverse effects on the nursing infant, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Neonates with a history of in utero exposure to candesartan cilexetil and hydrochlorothiazide tablets:
If oliguria or hypotension occurs, direct attention toward support of blood pressure and renal perfusion. Exchange transfusions or dialysis may be required as a means of reversing hypotension and/or substituting for disordered renal function.
Safety and effectiveness in pediatric patients have not been established.
Candesartan Cilexetil and Hydrochlorothiazide
Candesartan cilexetil and hydrochlorothiazide tablets have been evaluated for safety in more than 2800 patients treated for hypertension. More than 750 of these patients were studied for at least six months and more than 500 patients were treated for at least one year. Adverse experiences have generally been mild and transient in nature and have only infrequently required discontinuation of therapy. The overall incidence of adverse events reported with candesartan cilexetil and hydrochlorothiazide tablets was comparable to placebo. The overall frequency of adverse experiences was not related to dose, age, gender, or race.
In placebo-controlled trials that included 1089 patients treated with various combinations of candesartan cilexetil (doses of 2-32 mg) and hydrochlorothiazide (doses of 6.25-25 mg) and 592 patients treated with placebo, adverse events, whether or not attributed to treatment, occurring in greater than 2% of patients treated with candesartan cilexetil and hydrochlorothiazide tablets and that were more frequent for candesartan cilexetil and hydrochlorothiazide tablets than placebo were: Respiratory System Disorder: upper respiratory tract infection (3.6% vs 3.0%); Body as a Whole: back pain (3.3% vs 2.4%); influenza-like symptoms (2.5% vs 1.9%); Central/Peripheral Nervous System: dizziness (2.9% vs 1.2%).
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