As-needed 20 mg is the stop, even when the cash quote looks cheap

As-needed Cialis stops at 20 mg, not at the cash slogan

As-needed Cialis stops at 20 mg in a calendar day. Food matters less than with sildenafil. The card splits that stop from the daily 5 mg row. It does not fill either bottle.

Daily 5 mg is a lane, not a second 20 mg Friday

Daily 5 mg holds a low steady level across a 17-hour half-life. It is not a license to add 20 mg on Friday. Monthly cash can favor daily 5 mg if you would otherwise repeat 20 mg several times a week - run the count, not the slogan.

Warehouse and chain bands for PRN 20 mg versus daily 5 mg

Walmart, Costco, Kroger, and Walgreens already show public coupon or warehouse bands. August 2026 snapshots. 20 mg PRN and 5 mg daily are different rows. ZIP moves the number.

Why Half-Life Changed the Conversation

Among oral PDE5 inhibitors, tadalafil is the long-acting anchor - chosen when patients prioritize window length, daily convenience, or combined ED/LUTS management.

Card note: before tadalafil, PDE5 therapy meant timing a dose to a anticipated encounter. After Cialis entered the market in 2003, some men chose a daily low dose so spontaneity did not require a kitchen-timer relationship with a pill.

The molecule also carries FDA approval for benign prostatic hyperplasia at 5 mg daily - shared smooth-muscle biology in bladder neck and corpus cavernosum, though the BPH indication rests on its own LUTS trials, not ED surrogate endpoints alone.

Adcirca 40 mg once daily for pulmonary arterial hypertension is a different product line with different tablet strengths. Dispensing errors between Adcirca 40 mg and Cialis 20 mg have harmed patients; verify NDC and indication at every fill.

Card note: cost and insurance prior authorization often push men back to generic sildenafil despite preference for long duration. When coverage allows, tadalafil daily 2.5-5 mg is popular among men who also want morning erectile readiness and BPH symptom relief in one tablet.

Residents sometimes assume longer half-life equals stronger peak effect. It does not - peak concentrations after PRN doses resemble other agents; the difference is sustained sub-therapeutic tail that keeps tissue PDE5 inhibited for days with daily dosing.

Weekend dosing culture - 20 mg Friday and Sunday - is off-label in strict terms but pharmacologically predictable given 17.5-hour half-life; counsel that side effects may also persist across the week.

Card note: prior authorization battles often pit tadalafil daily against sildenafil PRN; document LUTS co-benefit when BPH indication applies to strengthen medical necessity.

Liquid tadalafil compounding exists for niche populations but standard tablets dominate; crushed tablets for dysphagia lack bioequivalence data - use commercial ODT alternatives in other drug classes when available, not applicable to standard Cialis.

Men with ED and cardiovascular disease often take statins and antiplatelets; tadalafil does not block platelet aggregation at ED doses - chest pain during sex still warrants ACS workup, not attribution to PDE5 alone.

Tadalafil exposure in hepatic cirrhosis Child-Pugh B justifies 5 mg daily cap or 10 mg PRN max; Child-Pugh C is essentially off limits because AUC rises unpredictably into hypotensive territory.

Insurance quantity limits of four 20 mg tablets monthly frustrate frequent users - daily 2.5 mg yields thirty tablets per month with lower peak myalgia and may satisfy plan limits differently; verify benefit design.

Concurrent moderate alcohol use with tadalafil PRN is not contraindicated but orthostatic dizziness reports increase when binge drinking precedes intercourse - separate pharmacology from behavioral ED contributors.

Same Pathway, Different Residence Time

Card note: tadalafil binds PDE5 and slows cGMP hydrolysis in corpus cavernosum smooth muscle exactly like sildenafil and vardenafil. Sexual stimulation remains mandatory for clinically meaningful erection.

Biochemical selectivity differs at the margins. Tadalafil shows relatively less PDE6 inhibition at comparable PDE5 occupancy, which may explain lower reported visual disturbance rates in some comparative surveys - though cross-study comparison is imperfect.

Card note: pDE11 inhibition is more prominent for tadalafil than for sildenafil at therapeutic exposures. PDE11 is expressed in skeletal muscle, prostate, and testis. Myalgia and back pain in phase III - sometimes delayed 12-24 hours after dose - likely trace partly to this isoform cross-reactivity.

Daily low-dose regimens achieve steady-state where trough PDE5 inhibition remains high enough that some men report improved baseline penile hemodynamics. This underpins penile rehabilitation research after prostatectomy, though outcomes remain mixed in published trials.

Systemic vasodilation produces mild blood pressure reduction and flushing. Hemodynamic synergy with nitrates is identical in principle to other PDE5 agents - duration of contraindication after last dose is longer because drug persists.

Do not co-prescribe with riociguat. Guanylate cyclase stimulation plus PDE5 blockade duplicates the nitrate risk profile through parallel cGMP elevation.

Smooth muscle relaxation in the prostate and bladder neck shares biochemistry with cavernosal tissue - explaining why one 5 mg daily tablet can address ED and LUTS without doubling exposure.

Tadalafil does not inhibit PDE5 continuously at full occupancy with daily 2.5 mg - trough levels maintain partial inhibition sufficient for many men while limiting peak myalgia.

Animal models show PDE5 in pulmonary vasculature; Adcirca 40 mg exploits that for PAH - an exposure tier never appropriate for ED tablets.

PDE11 is expressed in skeletal muscle; myalgia after tadalafil 20 mg PRN may reflect peak plus trough combined inhibition over 48 hours - switching to daily 2.5 mg lowers peak while maintaining some trough inhibition.

Tadalafil does not require dosing on an empty stomach - the practical win for dinner dates is real and measurable in patient satisfaction surveys, even when IIEF scores match sildenafil in crossover designs.

Guanylate cyclase stimulator riociguat contraindication applies identically - half-life extension means longer minimum interval before riociguat initiation after last tadalafil dose than after sildenafil.

PDE5 mRNA expression in corpus cavernosum is androgen-modulated in animal data; hypogonadal men on daily tadalafil still need testosterone evaluation if libido remains absent despite improved rigidity.

17.5 Hours Changes Everything

Oral tadalafil reaches peak plasma concentration in about 2 hours on average (range 0.5-6 h). Food does not materially alter rate or extent of absorption - a meaningful practical advantage over sildenafil and vardenafil for dinner-date scenarios.

Terminal elimination half-life is approximately 17.5 hours in healthy adults, supporting once-daily regimens without wild peak-trough swings at steady state for 2.5 and 5 mg daily doses.

Bioavailability has not been stated as precisely as sildenafil's 41%, but exposure increases dose-proportionally across the 2.5-20 mg range in registration studies. Hepatic metabolism via CYP3A4 dominates; no active metabolite contributes meaningfully to effect.

Steady state for daily dosing is reached in about 5 days. PRN users who take 20 mg only on weekends still carry detectable drug midweek - relevant when starting a strong CYP3A4 inhibitor or planning nitrate use in acute coronary syndrome.

Card note: renal impairment modestly increases exposure; severe hepatic impairment (Child-Pugh class C) has limited data and warrants conservative dosing. Dialysis studies show negligible removal.

Because elimination is slow, missed daily doses do not cause abrupt loss of effect the next morning; many men skip weekends intentionally when using daily therapy - acceptable clinically though not how label trials were structured.

Hepatic impairment: mild (Child-Pugh A) - no adjustment; moderate (B) - max 10 mg PRN or 5 mg daily per label tables; severe (C) - avoid.

Asian subpopulation PK analyses in regulatory files showed modestly higher exposure at same dose in some cohorts - not a separate label dose but worth noting if side effects cluster.

Tadalafil is not appreciably removed by hemodialysis; CrCl 30-50 mL/min limits daily use but PRN remains an option with monitoring.

Steady-state AUC after 5 mg daily is roughly equivalent to 25% of single 20 mg PRN AUC in crossover PK studies - explains lower myalgia with daily despite continuous tissue exposure.

Card note: cmax after 20 mg PRN averages near 400 ng/mL in label tables with wide inter-subject variability - same person gets consistent response once food and timing are controlled.

PRN Trials, Daily Trials, and BPH Data

FDA labeled both PRN and daily ED regimens - a flexibility no other PDE5 inhibitor matches at the same breadth.

Registration for ED used randomized placebo-controlled designs with IIEF erectile function domain and sexual encounter profile diaries. PRN doses of 10 and 20 mg separated from placebo across diverse ED etiologies.

Twenty milligrams PRN produced the largest IIEF improvements and intercourse success rates - similar class magnitude to sildenafil 100 mg in indirect comparisons - with the differentiator being duration, not peak efficacy.

Card note: daily 2.5 mg and 5 mg trials demonstrated that men could achieve successful intercourse at 24-hour intervals without planning dose to encounter. Spontaneity scores and partner satisfaction measures favored daily regimens in some secondary analyses.

BPH approval rested on International Prostate Symptom Score improvements with 5 mg daily over 12-week trials, including men with and without comorbid ED. Orthostatic hypotension monitoring matters when combining with alpha-blockers already on board for LUTS.

PAH data with Adcirca 40 mg daily showed improved 6-minute walk distance in class II-III disease - a hemodynamic indication unrelated to erectile dosing. Never use PAH exposure to treat ED.

Diabetic, spinal cord injury, and antidepressant-associated ED subgroups still beat placebo, with attenuated absolute response as with other PDE5 agents. Post-prostatectomy rehabilitation trials with daily tadalafil show mixed rigidity outcomes; guideline support exists but is not universal.

Head-to-head patient preference studies often split evenly between sildenafil and tadalafil - duration versus familiarity, cost, and side-effect profile drive choice more than IIEF point differences.

The OAD (once-a-day) registration program used intercourse attempt diaries without requiring dose timing to encounter - a paradigm shift from sildenafil's 'one hour before' language.

Card note: lUTS trials measured IPSS total and irritative/obstructive subscores; improvements were statistically significant by week 4 at 5 mg daily with sustained benefit through 12 weeks.

PAH 6-minute walk distance gains with 40 mg Adcirca were modest in absolute meters but clinically meaningful in class II-III WHO functional class - unrelated to ED endpoints.

IPSS improvement with 5 mg daily tadalafil was detectable by week 4 and sustained at week 12 in BPH registration trials - urology clinics sometimes start tadalafil before alpha-blocker when ED coexists and BP allows.

Partner satisfaction secondary endpoints in daily tadalafil trials favored active drug over placebo even when male IIEF gains were modest - spontaneity has dyadic value not captured in rigidity alone.

Registration trial inclusion criteria required documented ED for six months and stable relationship - generalizability to casual partners or post-divorce dating is extrapolated, not trial-proven, though PK does not change.

IIEF-EF domain baseline means near 13-14 in pivotal tadalafil PRN trials; active 20 mg arms improved mean scores by 6-9 points versus placebo at 12 weeks - crossing thresholds many urologists use for clinically meaningful change.

Sexual Encounter Profile question 3 (successful penetration) and question 4 (successful intercourse) both improved at 10 and 20 mg versus placebo with odds ratios roughly 2-3 in meta-analytic summaries.

Men with prior sildenafil success switching to tadalafil PRN in open-label extensions reported high satisfaction primarily due to extended window rather than higher peak rigidity scores on IIEF.

BPH trials excluded men with prior prostate surgery and PSA above 10 ng/mL - LUTS indication applies to moderate symptoms in medically screened populations, not post-TURP retention scenarios without specialist input.

PRN vs Daily vs BPH - Pick One Lane

ED as needed: 10 mg before anticipated activity; may increase to 20 mg based on response and tolerability. Maximum once per 24 hours.

ED once daily: 2.5 mg every day without regard to timing of intercourse; may increase to 5 mg daily if 2.5 mg insufficient.

BPH with or without ED: 5 mg once daily - same tablet strength as the higher daily ED dose; do not double with separate PRN 20 mg the same day without physician oversight.

With moderate CYP3A4 inhibitors (e.g., erythromycin), daily dose should not exceed 5 mg; PRN max 10 mg. With potent inhibitors (ketoconazole, ritonavir), daily max 2.5 mg; PRN max 10 mg and avoid daily/PRN mixing without specialist input.

Renal impairment: CrCl 30-50 mL/min - daily dosing not recommended per label; PRN regimens may proceed with caution. CrCl <30 or hemodialysis: avoid daily; PRN not formally studied - use low PRN with caution.

Card note: adcirca for PAH: 40 mg once daily only. Cialis maximum for ED is 20 mg PRN or 5 mg daily - fourfold and eightfold mismatches versus PAH exposure.

Splitting 20 mg tablets for daily 2.5 mg economizes but is not precision dosing - prefer commercial 2.5 mg when available for adherence tracking.

Morning versus evening daily dosing shows similar steady state; pick a time tied to routine (tooth brushing) to reduce missed doses.

Do not combine daily 5 mg BPH dose with same-day 20 mg PRN without physician instruction - total daily exposure can exceed studied regimens.

Ketoconazole 400 mg daily with tadalafil 20 mg PRN raised tadalafil AUC about 4-fold in interaction studies - label caps PRN at 10 mg and daily at 2.5 mg when potent inhibitor cannot be stopped.

Ritonavir-boosted protease inhibitor regimens for HIV require lowest tadalafil dose tier - review whenever ART regimen switches in multidisciplinary clinic.

CYP3A4 and the Long Washout Problem

Long half-life means interactions and contraindications outlast the sexual encounter - document last dose time in the chart when admitting patients.

Nitrates and nitrites remain absolutely contraindicated. Because tadalafil persists, many clinicians use a longer conservative interval - often 48 hours - before nitrates in ACS, though exact timing should follow current label and cardiology protocol.

Potent CYP3A4 inhibitors raise tadalafil exposure; dose caps in labeling are mandatory. Grapefruit juice in large quantities inhibits intestinal CYP3A4 - mention it to men who drink liters daily.

Tadalafil is a mild CYP3A4 inhibitor itself at supratherapeutic exposures; clinically relevant increases in simvastatin or bosentan levels are possible at PAH doses more than ED doses - still worth checking new statin starts.

Alpha-blockers for BPH (tamsulosin, alfuzosin) combined with tadalafil 5 mg daily were studied with orthostatic vitals monitoring; symptomatic hypotension can occur especially after first doses. Initiate when alpha-blocker is stable.

Antihypertensives generally add small BP reductions; most men tolerate combination. Riociguat - contraindicated. PDE5 inhibitor stacking (sildenafil plus tadalafil) is reckless and unstudied - prohibit it.

Because tadalafil inhibits its own clearance weakly at high doses, supratherapeutic exposure from drug-drug stacks lingers days - longer washout before surgery or nitrate exposure than with sildenafil.

Bosentan and tadalafil co-administration in PAH is studied; ED doses rarely overlap but men on PAH regimens should not receive duplicate Cialis.

Card note: macrolide antibiotics vary: clarithromycin is potent 3A4 inhibitor; azithromycin is weaker - adjust tadalafil dose only for strong inhibitors.

Card note: rifampin co-administration can reduce tadalafil exposure substantially - men on TB therapy may notice ED treatment failure until rifampin stops; temporary non-oral ED options may be needed.

Daily tadalafil 5 mg with moderate CYP3A4 inhibitor caps at 2.5 mg daily per label - recalculate whenever HIV or antifungal regimens change.

Myalgia, Back Pain, and Class Risks

Headache, dyspepsia, back pain, and myalgia dominate tadalafil-specific AE tables. Back pain and myalgia may appear delayed - a day after dose - consistent with PDE11-related skeletal muscle effects in some hypotheses.

Card note: flushing and nasal congestion follow vasodilation. Visual disturbance rates are lower than sildenafil in some trials but sudden NAION and sudden hearing loss remain class warnings applicable to all PDE5 inhibitors.

Priapism incidence is low but unchanged in mechanism - counsel high-risk hematologic patients identically to other agents.

Daily dosing spreads side effects across the week: some men notice mild leg ache on day two of first week then adapt; others switch to PRN to avoid continuous myalgia.

Cardiovascular serious AEs in cleared populations mirror placebo rates in trials. Unstable cardiac disease remains a reason to defer sexual activity altogether, not merely to switch PDE5 agents.

Facial edema and gastroesophageal reflux appear in post-marketing data at low frequency - distinguish from angioedema and stop if airway involved.

Myalgia sometimes responds to dose reduction from 20 mg PRN to 10 mg or switch to daily 2.5 mg with lower peak.

NAION risk remains unquantified per agent; document monocular vision change timing if reported.

Back pain incidence in tadalafil 20 mg PRN arms approached 6% versus 2% placebo in pooled phase III - delayed onset 12-48 hours post dose distinguishes from mechanical back strain.

Card note: flushing with daily 5 mg often fades after two weeks at steady state while LUTS benefit persists - warn patients not to quit before adaptation week.

Elderly, Hepatic, Renal, Diabetes, and LUTS Overlap

No strict age cap exists, but elderly men on multiple antihypertensives feel orthostatic symptoms more with daily 5 mg - start 2.5 mg daily or 10 mg PRN when polypharmacy is heavy.

Mild-to-moderate hepatic impairment (Child-Pugh A/B): no adjustment for daily 2.5 mg; use caution at 5 mg daily or 20 mg PRN. Child-Pugh C: avoid use - insufficient data.

CrCl 30-50 mL/min: avoid daily tadalafil per label; PRN may be considered. CrCl <30: daily contraindicated; PRN not studied - if used, lowest PRN with monitoring.

Diabetes: subgroup efficacy persists versus placebo; combine with GLP-1 or SGLT2 cardiometabolic benefits when appropriate - ED improvement does not treat glucose.

Card note: men with BPH on alpha-blockers initiating 5 mg daily tadalafil need seated and standing BP checks at first co-administration week.

Post-prostatectomy daily tadalafil for rehabilitation is common off-label usage with urology backing; set realistic rigidity expectations and time horizon (months, not days).

Benign prostatic hyperplasia with severe outlet obstruction may still need urological procedures despite IPSS improvement - tadalafil treats symptoms, not mechanical blockage from large median lobe.

Card note: alpha-blocker-naive men starting 5 mg daily for BPH should watch for first-dose orthostasis; unlike tamsulosin, tadalafil lacks selective alpha-1A profile but still vasodilates.

Pediatric and adolescent use is off-label for ED; Adcirca has pediatric PAH dosing - keep products separated in household with teens on PAH therapy.

Card note: crCl 30-50 mL/min: avoid daily tadalafil per label; PRN 10 mg may be used with caution - document renal function annually because CKD progression changes eligibility.

Benign prostatic hyperplasia with 5 mg daily may reduce need for tamsulosin in some men - urology sometimes de-escalates alpha-blocker after three months of combined symptom improvement; monitor orthostasis during transitions.

Pharmacy Counter and Exam Room Scripts

'Can I take it only on Fridays?' - PRN 10-20 mg works that way; daily 5 mg also allows Friday-only use pharmacologically but label trials assumed continuous daily intake for LUTS.

'Why does my back hurt Tuesday after Saturday night?' - Delayed myalgia happens; try PRN lower dose or switch agents if it persists across three cycles.

'Is this the 36-hour pill?' - Marketing shorthand. Plan for a window, not a stopwatch guarantee; arousal still required.

Insurance denials: document failed sildenafil trial if step therapy required. Generic tadalafil pricing fluctuates - check GoodRx-class tools with patients when cash pay.

Card note: separate Adcirca from Cialis in pill organizers; color and strength confusion has caused emergency visits for hypotension.

Nitrate contraindication lasts longer than with sildenafil - update wallet cards and EMS instructions accordingly.

Card note: 'Will daily hurt my heart?' - Trial BP effects are small in normotensive men; still avoid if sex is contraindicated for cardiac reasons.

Travel across time zones: daily dosing by home-clock time avoids trough gaps; PRN travelers often prefer long half-life for flexibility.

Card note: employers and insurers sometimes cap quantity to eight PRN tablets monthly - daily 2.5 mg may be cheaper per act of intercourse for frequent users; run the math with patients paying cash.

Morning erections may increase on daily tadalafil independent of intercourse plans - patients sometimes report improved nocturnal rigidity within two weeks; distinguish physiologic from pathologic priapism if morning erection exceeds four hours.

Tadalafil for BPH does not shrink prostate volume - symptom relief is smooth muscle mediated; PSA monitoring schedules continue unchanged when starting 5 mg daily for LUTS.

When Tadalafil Wins - and When It Does Not

Choose tadalafil when patients want long PRN window, daily spontaneity, or combined ED and BPH symptom control at 5 mg daily.

Half-life near 17.5 hours drives interaction duration and delayed myalgia; food does not blunt absorption - practical win for meals and dates.

PRN: 10-20 mg max once daily. Daily ED: 2.5-5 mg. BPH: 5 mg. PAH: Adcirca 40 mg - never mix product lines.

Card note: cYP3A4 inhibitors force dose caps; nitrates and riociguat remain forbidden with extended washout caution.

Side-effect profile adds back pain and myalgia to the usual vasodilatory list; vision and hearing class warnings persist.

If myalgia or cost limits use, shorter-acting agents remain effective - class failure is less common than side-effect intolerance.

Adcirca 40 mg and Cialis 20 mg look similar in color on some generic lines - verify NDC at every fill.

Card note: daily 5 mg is the only PDE5 regimen dual-labeled for ED and BPH - use that when both complaints present.

Regulatory labeling for tadalafil explicitly notes that the 36-hour marketing window reflects half-life math plus tissue PDE5 occupancy models - not a guarantee of 36 hours of erection. Patients who expect a full weekend erection without stimulation will be disappointed regardless of PK.

Card note: when switching from sildenafil 100 mg PRN to tadalafil daily, washout is not mandatory but overlapping doses on the same day adds vasodilator load without proven benefit - pick a switch date and start daily 2.5 or 5 mg the next morning.

Card note: european Medicines Agency summaries mirror FDA half-life and dose cap data; travelers carrying tadalafil across borders should keep pharmacy labels to avoid customs confusion with unlabeled tablets.

Tadalafil 20 mg PRN label allows consideration of 5 mg daily alternative when frequent intercourse makes daily cheaper - run monthly tablet count with patient paying out of pocket.

Lower urinary tract symptoms improvement on 5 mg daily does not replace indication for 5-alpha reductase inhibitor when prostate volume exceeds 40 mL and PSA is rising - combination therapy is common in urology.

Card note: phase III OAD trial primary endpoint was successful intercourse attempt at 24-hour intervals regardless of timing - fundamentally different statistical question than sildenafil one-hour-before design.

Card note: adcirca 40 mg once daily for PAH produces mean tadalafil exposure roughly eightfold higher than Cialis 5 mg daily at steady state - the products are not dose-linear across indications.

Crossover PK studies show accumulation ratio near 1.6 for daily 5 mg after day 10 versus day 1 - steady state matters when interpreting first-week side effects versus maintenance phase.

Men on 5-alpha reductase inhibitor for six months with persistent LUTS and new ED may receive tadalafil 5 mg daily as dual-purpose add-on without stopping finasteride - watch orthostasis if alpha-blocker also present.

Card note: prior myocardial infarction more than 90 days ago with stable exercise tolerance is not an automatic PDE5 contraindication in contemporary guidance - tadalafil daily does not replace cardiology risk stratification before resuming sexual activity.

IPSS reduction of 3-4 points at 12 weeks on 5 mg daily met prespecified minimally important difference thresholds in BPH registration statistical plans - urologists use this when deciding medical versus surgical LUTS management.

Tadalafil 20 mg PRN taken on Friday evening may still produce measurable plasma levels Monday morning - relevant for elective surgery scheduling and for nitrate timing if chest pain occurs mid-week.

Generic tadalafil film-coated tablets from multiple ANDA holders passed fasting bioequivalence; food independence carries across generics unlike sildenafil high-fat counseling intensity.

Once-daily tadalafil for ED was non-inferior to PRN 20 mg for IIEF in some comparative trials while improving spontaneity subscores - neither arm beat the other on rigidity alone.

Hepatic first-pass extraction is moderate for tadalafil; unlike sildenafil, strong CYP3A4 inhibition produces multi-day exposure tail - plan dose reductions before starting itraconazole for onychomycosis in man already on Cialis daily.

Card note: daily tadalafil 5 mg for BPH reduced nocturia episodes in secondary analyses of LUTS trials - sleep quality improvement is patient-valued outcome beyond IPSS score alone.

Tadalafil PRN 20 mg onset for intercourse planned same evening can be taken at lunch without food restriction - contrast explicitly with sildenafil steakhouse counseling when patients switch agents.

WHO PAH functional class improvements with Adcirca were supported by hemodynamic catheter data substudies - ED prescribers rarely see those data but should know PAH is separate evidence package.

Tadalafil 2.5 mg daily is the lowest maintenance ED dose - useful in men who get 20 mg PRN headache but want daily spontaneity at reduced peak exposure.

Concurrent PDE5 use with soluble guanylate cyclase stimulators beyond riociguat is not applicable - riociguat remains the sole labeled GC stimulator contraindication pair in U.S. labeling.

Finasteride-associated ED may improve with tadalafil while on 5-alpha reductase inhibitor - dual therapy for LUTS and ED is common without stopping finasteride.