Increased antihypertensive effect w/ TCAs, α-blockers, diuretics. Amlodipine: Increased bioavailability w/ grapefruit/grapefruit juice. Increased exposure w/ CYP3A4 inhibitors eg, PIs, azole antifungals, macrolides, verapamil, diltiazem. Decreased conc w/ CYP3A4 inducers eg, anticonvulsants, rifampicin,
H. perforatum. Increased exposure of simvastatin. Avoid co-administration w/ dantrolene (infusion). Valsartan: Increased lithium conc. Increased K levels w/ K-sparing diuretics, K supplements, K-containing salt substitutes & other substances that may increase K levels. Attenuated antihypertensive effect w/ NSAIDs including selective COX-2 inhibitors, acetylsalicylic acid (>3 g/day) & nonselective NSAIDs. Increased systemic exposure w/ inhibitors of uptake transporter (rifampicin, ciclosporin) or efflux transporter (ritonavir). Dual blockade of the renin-angiotensin-aldosterone system w/ ACE inhibitors, angiotensin receptor blockers, or aliskiren.