Tadalafil (Generic) Cannabis Interaction Profile: What You Need to Know

What product and label does this page cover?

This page is about generic tadalafil 2.5 to 20 mg tablets for erectile dysfunction and benign prostatic hyperplasia. FDA-approved generic tadalafil tablets in these strengths follow the Cialis indications for erectile dysfunction and benign prostatic hyperplasia [3]. The label-based interaction and warning information below comes from the Cialis label [1].

What do the cannabis-related reports show?

The closest published evidence is a 2020 systematic review focused on sildenafil and cannabis. Its search terms also included tadalafil and other PDE5 inhibitors. It found 13 papers; 5 examined cannabis plus sildenafil, and 3 linked that combination to cardiovascular events: one posterior myocardial infarction without a Q wave, one myocardial infarction without ST elevation, and one acute coronary syndrome. Those cardiovascular cases involved sildenafil, a different PDE5 inhibitor, not tadalafil [4].

A 2025 forensic toxicology review of 21 chemsex-related deaths in the United Kingdom recorded sildenafil or tadalafil in 9 cases and cannabis in 3 [5]. Detection counts in a small case series are not a test of how the two drugs behave together.

What does the Cialis label say about blood pressure?

Tadalafil is a PDE5 inhibitor and a mild systemic vasodilator [1]. In healthy volunteers, tadalafil 20 mg produced a mean maximal fall in supine blood pressure, relative to placebo, of 1.6/0.8 mm Hg [1].

The Cialis label describes the effect of adding other vasoactive drugs and alcohol:

• Alcohol. Substantial consumption, meaning 5 units or greater, can increase orthostatic signs and symptoms, including increased heart rate, decreased standing blood pressure, dizziness and headache [1]. Tadalafil did not change alcohol plasma concentrations, and alcohol did not change tadalafil concentrations [1].
• Antihypertensives. Small reductions in blood pressure occurred when tadalafil was given with amlodipine, angiotensin II receptor blockers, bendroflumethiazide, enalapril or metoprolol, compared with placebo [1].
• Alpha-blockers. Alpha-blockers and tadalafil are both vasodilators, so an additive blood-pressure effect is anticipated [1]. For erectile dysfunction, the label says a man should be stable on the alpha-blocker first and tadalafil should be started at the lowest dose; for benign prostatic hyperplasia the label does not recommend the combination [1].

The label also says erectile dysfunction treatments, including Cialis, should not be used in men for whom sexual activity is inadvisable because of cardiovascular status [1].

Does CBD or THC change tadalafil levels?

Tadalafil is metabolized mainly by CYP3A4. Ketoconazole 400 mg daily raised single-dose tadalafil 20 mg exposure (AUC) by 312% and peak concentration by 22%; for use with CYP3A4 inhibitors, the Cialis label limits as-needed tadalafil to 10 mg no more often than every 72 hours and once-daily tadalafil to 2.5 mg [1].

Cannabinoids are handled by some of the same enzymes. In vitro work identifies CYP2C9 and CYP3A4 as contributors to THC metabolism and CYP2C19 and CYP3A4 for CBD [2]. A systematic review of exogenous cannabinoids as substrates, inhibitors and inducers concluded that the inhibition and induction data for THC, CBD and cannabinol generally reflect a low risk of clinically significant drug interactions with most use, but that specific human data are lacking [2]. The same review found that smoked cannabis herb likely induces CYP1A2-mediated theophylline metabolism, though whether cannabinoids themselves cause that effect is questionable [2].

The FDA has not approved a marketing application for cannabis for the treatment of any disease; it has approved purified CBD (Epidiolex) for certain seizure disorders and the synthetic cannabinoids dronabinol and nabilone [6]. The agency states that unapproved cannabis and cannabis-derived products can have unpredictable and unintended consequences, including serious safety risks [6].

Does the dosing schedule matter?

For erectile dysfunction, the Cialis label lists 10 mg before anticipated sexual activity as the as-needed starting dose, with 5 mg or 20 mg as adjustments based on efficacy and tolerability, and no more than once per day. For once-daily use it lists 2.5 mg, which may be increased to 5 mg, and it lists 5 mg once daily for benign prostatic hyperplasia and for erectile dysfunction with benign prostatic hyperplasia [1].

The mean terminal half-life is 17.5 hours, and the label reports improved erectile function compared with placebo for up to 36 hours after a dose [1]. That describes erectile function, not a continuous erection; sexual stimulation is still required [1]. With once-daily dosing, steady state is reached within 5 days at exposure about 1.6-fold that of a single dose, and the label tells prescribers to treat daily use as continuous plasma tadalafil levels when weighing interactions with nitrates, alpha-blockers, antihypertensives, potent CYP3A4 inhibitors and substantial alcohol [1].

What emergency warnings apply to tadalafil?

The label says an erection lasting more than 4 hours, painful or not, needs emergency medical attention, and that priapism, a painful erection lasting more than 6 hours, can cause irreversible damage to erectile tissue [1]. It says patients should stop Cialis and seek medical attention for a sudden loss of vision in one or both eyes, which may be non-arteritic anterior ischemic optic neuropathy, and for a sudden decrease or loss of hearing [1].