Sildenafil Alpha blockers

Concomitant use with alpha-blockers Do not take 50 or 100 mg doses of sildenafil within 4 hours of alpha-blocker administration. A 25 mg dose of sildenafil may be taken at any time. 

Avoid faking sildenafil wifhin 4 hr of an alpha-blocker... 

Caution [C, ] CrCl <30 Contra Component sensitivity, asthma, severe COPD, sinus bradycardia Disp Soln SE Irritation, bitter taste, superficial keratitis, ocular allergic Rxn EMS Drug is absorbed systemically OD May cause electrolyte disturbances (K), acidosis and bradycardia monitor ECG Doxazosin (Cardura, Cardura XL) [Antihypertensive/Alpha Blocker] Uses HTN symptomatic BPH Action < [-Adrenergic blocker relaxes bladder neck smooth muscle Dose HTN Initial 1 mg/d PO may be T to 16 mg/d PO BPH Initial 1 mg/d PO, may T to 8 mg/d XR 2-8mg qAM Caution [B, ] Use w/ PDE5 inhibitor (eg, sildenafil) can cause 1 BP Contra Component sensitivity Disp Tabs SE Dizziness, HA, drowsiness, sexual dysfxn, doses >4 mg T postural BP risk Interactions T Effects W/ nitrates, antihypertensives, EtOH i effects W/ NSAEDs, butcher s broom -t effects OF clonidine EMS Concurrent EtOH use can T drowsiness syncope may occur w/in 90 min of initial dose OD May cause profound hypotension place pt in supine position, give IV fluids, use pressors if needed... 

ALPHA-BLOCKERS PHOSPHODIESTERASE TYPE S INHIBITORS Risk of marked 1 BP Additive hypotensive effect Avoid co-administration. Avoid alpha-blockers for 4 hours after intake of sildenafil (6 hours after vardenafil)... 

The manufacturers recommend that patients should be stable on an alpha blocker before sildenafil is started and that consideration should be given to starting sildenafil at the lowest dose (25 mg). " The UK manufacturer notes that a hypotensive effect is most likely within 4 hours of taking an alpha blocker. When starting an alpha blocker in a patient taking sildenafil, the US manufacturer states that the alpha blocker should be started at the lowest dose. ... 

No clinically relevant interactions appear to occur between sildenafil, tadalafil or vardenafil and most antihypertensive drugs. The exceptions may be diltiazem and verapamil. The potentially serious interactions of sildenafil, tadalafil and vardenafil with the alpha blockers and nitrates are discussed elsewhere. See Phosphodiesterase type-5 inhibitors + Alpha blockers , p.l268 and Phosphodiesterase type-5 inhibitors -I- Nitrates , p.l272. 

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