Can you take Sildenafil (Viagra) and Tadalafil (Cialis) together?

The available evidence is use- and population-specific. Each page documents mechanism, studied or reported dose context, risks, and legal status; the database does not determine whether a combination is appropriate for an individual.

Rankings / Comparisons

Sildenafil (Viagra) vs Tadalafil (Cialis)

Short-acting vs long-acting PDE5 inhibitors — dosing strategy, side-effect profile, and off-label cardiovascular interest.

Reviewed by Read Off Label · How we grade

Score comparison

Tadalafil (Cialis) has the higher descriptive composite (S, 8.8/10) compared with Sildenafil (Viagra) (A, 8.0/10). The axes below show whether that difference comes from evidence, reported benefit, safety, or a combination.

Sildenafil (Viagra)

A 8.0/10

Evidence: Very Strong (erectile dysfunction; also pulmonary arterial hypertension); emerging longevity signal (observational — lower Alzheimer's risk in PDE5i users) (10/10)
Benefit: Very Strong (10/10)
Risk: Low-Med (headache, flushing, nasal congestion, dyspepsia, blue-tinge vision; contraindicated with nitrates — fatal hypotension; caution with alpha-blockers) (5/10 safety)
Legality: Rx; generics widely available; Hims/Roman-style telehealth
Dose / route context: 25-100 mg PO 30-60 min before activity; fasting administration produces faster onset
Class: Prescription
Last reviewed: Jul 23, 2026

Read Off Label grades Sildenafil (Viagra) as A (8.0/10) based on very strong evidence, very strong benefit magnitude, and a low-med-risk safety profile.

Generic since 2017 — dramatic price drop.

Studied, labeled, or reported-use context: 25-100 mg PO 30-60 min before activity; fasting administration produces faster onset — Rx; generics widely available; Hims/Roman-style telehealth; not individualized guidance.

What it is

Generic since 2017 — dramatic price drop. Fang 2021 and others show observational Alzheimer risk reduction in PDE5i users — mechanism via cerebral blood flow and Aβ modulation plausible. A high-fat meal delays absorption by more than one hour. Concomitant nitrates can cause severe hypotension and are contraindicated in prescribing information. A sildenafil oral film (Vybrique) gained FDA approval in 2026 as a more convenient dosing format.

Mechanism

Selective phosphodiesterase-5 inhibitor; prevents cGMP breakdown → sustained smooth muscle relaxation in corpus cavernosum → erection (upon sexual stimulation, not spontaneous); also pulmonary vasodilation

Full Sildenafil (Viagra) review →

Tadalafil (Cialis)

S 8.8/10

Evidence: Very Strong (ED; BPH/LUTS; PAH — Adcirca); emerging longevity signal shared with PDE5i class (10/10)
Benefit: Very Strong (10/10)
Risk: Low-Med (headache, back/muscle pain distinctive of tadalafil, nasal congestion; same nitrate contraindication) (7/10 safety)
Legality: Rx; generic since 2018
Dose / route context: 2.5-5 mg PO daily (daily regimen) or 10-20 mg on-demand
Class: Prescription
Last reviewed: Jul 23, 2026

Read Off Label grades Tadalafil (Cialis) as S (8.8/10) based on very strong evidence, very strong benefit magnitude, and a low-med-risk safety profile.

Long half-life makes daily low-dose dosing feasible ('weekender' branding).

Studied, labeled, or reported-use context: 2. — Rx; generic since 2018; not individualized guidance.

What it is

Long half-life makes daily low-dose dosing feasible ('weekender' branding). BPH approval at 5 mg daily is useful for older men with ED+LUTS. Back/muscle pain is characteristic (via PDE11 cross-inhibition). Same CV cautions and food effects less pronounced than sildenafil.

Mechanism

Same mechanism as sildenafil but with ~17.5-hr plasma half-life — allows daily low-dose use for continuous effect rather than as-needed; also FDA-approved for BPH symptoms

Full Tadalafil (Cialis) review →

Common questions

How do the evidence profiles of Sildenafil (Viagra) and Tadalafil (Cialis) compare?: Tadalafil (Cialis) has the higher descriptive composite (S, 8.8/10) compared with Sildenafil (Viagra) (A, 8.0/10). The axes below show whether that difference comes from evidence, reported benefit, safety, or a combination.
What's the difference between Sildenafil (Viagra) and Tadalafil (Cialis)?: Short-acting vs long-acting PDE5 inhibitors — dosing strategy, side-effect profile, and off-label cardiovascular interest.
Can you take Sildenafil (Viagra) and Tadalafil (Cialis) together?: The available evidence is use- and population-specific. Each page documents mechanism, studied or reported dose context, risks, and legal status; the database does not determine whether a combination is appropriate for an individual.

This is an independent synthesis of published research by a non-clinician. The comparison reports composite and axis-level differences without selecting an intervention for the reader. Relevance depends on indication, population, dose, duration, and other context. See the full disclaimer and methodology.