Lisinopril and Finasteride Interaction: What Patients and Clinicians Need to Know

Print or save as PDFOpens the printable medication review sheet and your print dialog. No sign-up.

The short answer

The finasteride label does not describe a problem with this pair. Its interaction section states that no drug interactions of clinical importance have been identified [1].

Finasteride metabolism

Finasteride has about 65% bioavailability, is about 90% protein bound, and is extensively metabolized in the liver, mainly by CYP3A4. Its mean terminal half-life is about 5 to 6 hours in men aged 18 to 60 and about 8 hours in men over 70 [1].

The label states that finasteride does not appear to affect the cytochrome P450-linked drug-metabolizing enzyme system. Compounds tested directly with it (antipyrine, digoxin, propranolol, theophylline and warfarin) showed no clinically meaningful interactions [1].

Finasteride is a CYP3A4 substrate, and the label's interaction section does not discuss CYP3A4 inhibitors or inducers [1]. That question concerns those drugs, not lisinopril.

Blood pressure

Lisinopril lowers blood pressure by blocking angiotensin-converting enzyme, and blood pressure is the effect it is prescribed for. The finasteride label puts no blood-pressure figure on the combination [1].

What the finasteride trials show is sexual. In three 12-month controlled trials of the 1 mg tablet (945 men on finasteride, 934 on placebo, aged 18 to 41), the drug-related reactions reported in 1% or more of users were decreased libido, erectile dysfunction and ejaculation disorder [1].

Finasteride side effects worth knowing

In those same three trials, 3.8% of men on finasteride (36 of 945) reported one or more sexual adverse effects versus 2.1% (20 of 934) on placebo (P=0.04). Discontinuation for drug-related sexual events was 1.2% versus 0.9%, and the incidence of each effect fell to 0.3% or lower by the fifth year of treatment [1].

The label's postmarketing section lists sexual dysfunction that continued after stopping, including erectile dysfunction, libido disorders, ejaculation disorders and orgasm disorders. It also lists male infertility and/or poor seminal quality, with normalization or improvement reported after discontinuation [1]. Since the August 2022 labeling change it also lists depression, suicidal ideation and behavior [2]. Propecia and Proscar carry no boxed warning. The labels state that these postmarketing reports are voluntary, come from a population of uncertain size, and that a causal relationship cannot reliably be established [1].

These are finasteride's own labeled effects, not effects the labeling attributes to combining it with lisinopril.

PSA testing while on finasteride

Finasteride lowers PSA, which matters for anyone also being monitored for prostate health. In men aged 18 to 41 taking 1 mg, mean PSA fell from 0.7 ng/mL to 0.5 ng/mL at month 12. The label says any confirmed increase from the lowest PSA value while on treatment should be evaluated for prostate cancer, even if the result is still in the normal range for men not taking a 5-alpha reductase inhibitor [1]. The 5 mg product lowers PSA by about 50% within six months, and that label advises doubling an isolated PSA value after six months of treatment so it can be compared with normal ranges [3].

Dosing and who it is for

Propecia is one 1 mg tablet once daily, with or without food. Daily use for three months or more is usually needed before benefit is seen, continued use is needed to keep it, and withdrawal leads to reversal of effect within 12 months [1].

Propecia is indicated for men only. The label warns that women who are or may become pregnant should not handle crushed or broken tablets because of potential risk to a male fetus [1].