PDE5 Inhibitors & Statins to Treat Cancer - Quick Reference Sheet

PDE5 Inhibitors & Statins to Treat Cancer

Created on 08/05/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 5 Audit

Two cheap medicines, a cholesterol drug and one first sold for erectile dysfunction, each cut a tumor cell's cholesterol supply at a different point, and blocking both did more in animals. No human study of the pair exists. Each carries a well-established benefit unrelated to the tumor. Safety is well understood; benefit against cancer is unproven. (Full Review)

Protocol

PDE5 inhibitor dosing as used in oncology studies
Sildenafil 50–100 mg or tadalafil 10–20 mg daily
At or above the top of the licensed erectile dysfunction range; the immune effect was largest at tadalafil 10 mg.
Statin dosing as used in oncology studies
Atorvastatin 40 mg daily
The dose that succeeded in the cardioprotection trial; simvastatin 40 mg failed in both phase 3 chemotherapy add-on trials.
Best time of day
Simvastatin evening, tadalafil morning
Atorvastatin and rosuvastatin have long half-lives and can be taken at any time. Tadalafil gives near-continuous PDE5 inhibition; sildenafil a pulsed exposure.
Time to effect
Cardiovascular event reduction
Years
Measurable cholesterol effect within 4–6 weeks; clinical event reduction accrues over years.
Vasodilatory effect
Immediate
The erectile and pulmonary vasodilatory effect is immediate.
Anti-tumor effect
No established timeline
No clinical endpoint has been shown to move, so no interval marks success or failure.

Benefits

Contraindications
  • Nitrates and nitric oxide donors (nitroglycerin, isosorbide mono- and dinitrate, amyl nitrite, nicorandil)
  • Soluble guanylate cyclase stimulators (riociguat)
  • Myocardial infarction within 90 days, stroke within 6 months, unstable angina, New York Heart Association Class III–IV heart failure
  • Resting systolic blood pressure below 90 mmHg, uncontrolled hypertension above 170/100 mmHg
  • Severe hepatic impairment (Child-Pugh Class C)
  • Retinitis pigmentosa or prior non-arteritic anterior ischemic optic neuropathy
  • Active statin-associated autoimmune myopathy
  • Sickle cell disease or other predisposition to priapism
  • Pregnancy or breastfeeding
  • Cancer cachexia with total cholesterol below 120 mg/dL
Key Interactions
  • Strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, ritonavir, cobicistat, grapefruit juice)
  • Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St. John's wort)
  • Alpha-adrenergic blockers (tamsulosin, doxazosin, alfuzosin)
  • Fibrates, particularly gemfibrozil
  • Ciclosporin, tacrolimus and other calcineurin inhibitors
  • Vitamin K antagonists (warfarin, acenocoumarol, phenprocoumon) and direct oral anticoagulants (apixaban, rivaroxaban, edoxaban, dabigatran)
  • Cimetidine, high-dose aspirin and non-steroidal anti-inflammatory drugs
  • Red yeast rice, berberine, niacin, high-dose fish oil, grapefruit-containing products
  • L-Citrulline, L-Arginine, beetroot or nitrate-rich juice, Panax ginseng, horny goat weed (Epimedium)
  • Coenzyme Q10 and high-dose vitamin E
  • Antihypertensives (amlodipine, lisinopril, bisoprolol), other phosphodiesterase inhibitors (dipyridamole, cilostazol), anthracycline chemotherapy (doxorubicin, epirubicin)

Risk & Side Effects

  • High: Statin-associated muscle symptoms; vasodilatory side effects of PDE5 inhibitors; new-onset type 2 diabetes; severe hypotension with nitrates or alpha-blockers
  • Medium: Rhabdomyolysis; hepatic transaminase elevation; visual disturbance from PDE6 cross-inhibition; back pain and myalgia from PDE11 cross-inhibition
  • Low: Non-arteritic anterior ischemic optic neuropathy and sudden hearing loss; melanoma association with PDE5 inhibitors; statin-associated autoimmune myopathy and cognitive symptoms; aggravated cancer-related wasting; priapism
  • Speculative: Blunting of immunotherapy through excessive cholesterol restriction in T cells; impaired gamma-delta T-cell and natural killer surveillance from mevalonate depletion

Monitoring

Marker Target Why
Total cholesterol 160–200 mg/dL Confirms the statin is working and flags over-depletion
LDL-C 60–100 mg/dL; below 70 mg/dL with cardiovascular disease Primary measure of statin effect and proxy for exposure
ApoB Below 80 mg/dL; below 60 mg/dL at high risk Tracks particle number, a better risk predictor than cholesterol mass
CK Below 200 U/L, and below twice the upper limit of normal The most important safety marker for the statin partner
ALT and AST Below 25 U/L in men, below 20 U/L in women Detects hepatic injury from the statin or chemotherapy
HbA1c Below 5.4% Detects the statin-associated glucose rise before diabetes
eGFR Above 90 mL/min/1.73 m² Sets the safe rosuvastatin dose; flags rhabdomyolysis kidney injury
hs-CRP Below 1.0 mg/L Tracks the statin's anti-inflammatory effect, partly independent of cholesterol lowering
Coenzyme Q10 0.8–1.2 µg/mL Identifies the depletion proposed to underlie statin muscle symptoms
Testosterone, total 500–900 ng/dL in men Cholesterol is the substrate for steroid hormone synthesis; low testosterone is common here
Blood pressure, seated and standing Above 100/60 mmHg seated; under 20 mmHg systolic drop on standing Detects orthostatic hypotension limiting PDE5 inhibitor dose escalation

Cadence: Fasting baseline panel before the first dose, including the one-off genetic test. Lipid, liver and muscle markers at 6–12 weeks after starting or any dose increase, again at 6 months, then every 6–12 months once stable. Glycated hemoglobin annually. Creatine kinase whenever new muscle symptoms appear. Blood pressure at every dose increase.

Qualitative Assessment

  • Muscle symptoms: New aching, weakness or tenderness in thighs, shoulders or calves, particularly if symmetrical and proximal.
  • Headache pattern: Headache after a PDE5 inhibitor dose that does not attenuate over the first two to three weeks.
  • Exercise capacity: A fall in endurance or longer recovery after training, preceding any change in creatine kinase.
  • Sleep quality: New insomnia or unusually vivid dreams after starting a lipophilic statin.
  • Vision and hearing: Any change in color perception, light sensitivity, visual field or hearing.
  • Energy and cognitive clarity: Persistent fatigue or subjective mental fogginess attributed to statins.