FINASTERIDE Drug Interactions: What You Need to Know

INTERACTIONS

7.1 Cytochrome P450-Linked Drug Metabolizing Enzyme System No drug interactions of clinical importance have been identified. Finasteride does not appear to affect the cytochrome P450-linked drug-metabolizing enzyme system. Compounds that have been tested in man include antipyrine, digoxin, propranolol, theophylline, and warfarin and no clinically meaningful interactions were found.

7.2 Other Concomitant Therapy Although specific interaction studies were not performed, finasteride doses of 1 mg or more were concomitantly used in clinical studies with acetaminophen, acetylsalicylic acid, α-blockers, analgesics, angiotensin-converting enzyme (ACE) inhibitors, anticonvulsants, benzodiazepines, beta blockers, calcium-channel blockers, cardiac nitrates, diuretics, H 2 antagonists, HMG-CoA reductase inhibitors, prostaglandin synthetase inhibitors (also referred to as NSAIDs), and quinolone anti-infectives without evidence of clinically significant adverse interactions.

Finasteride tablets are contraindicated in the following:

• Hypersensitivity to any component of this medication.
• Pregnancy. Finasteride use is contraindicated in females when they are or may potentially be pregnant. Because of the ability of Type II 5α-reductase inhibitors to inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT), finasteride may cause abnormalities of the external genitalia of a male fetus of a pregnant female who receives finasteride. If this drug is used during pregnancy, or if pregnancy occurs while taking this drug, the pregnant female should be apprised of the potential hazard to the male fetus. [See also Warnings and Precautions (5.3) , Use in Specific Populations (8.1) , How Supplied/Storage and Handling (16) and Patient Counseling Information (17.2) .] In female rats, low doses of finasteride administered during pregnancy have produced abnormalities of the external genitalia in male offspring. Hypersensitivity to any components of this product ( 4 ). Females who are or may potentially be pregnant ( 4 , 5. 3, 8.1 , 16 ).(4)

AND PRECAUTIONS

• Finasteride tablets reduces serum prostate specific antigen (PSA) levels by approximately 50%. However, any confirmed increase in PSA while on finasteride tablets may signal the presence of prostate cancer and should be evaluated, even if those values are still within the normal range for men not taking a 5α-reductase inhibitor ( 5.1 ).
• Finasteride tablets may increase the risk of high-grade prostate cancer ( 5.2 , 6.1 ).
• Females should not handle crushed or broken finasteride tablets when they are pregnant or may potentially be pregnant due to potential risk to a male fetus ( 5.3 , 8.1 , 16 ).
• Finasteride tablets are not indicated for use in pediatric patients or females ( 5.4 , 8.1 , 8. 2, 8.4 , 12.3 ).
• Prior to initiating treatment with finasteride tablets for BPH, consideration should be given to other urological conditions that may cause similar symptoms ( 5.6 ).

5.1 Effects on Prostate Specific Antigen (PSA) and the Use of PSA in Prostate Cancer Detection In clinical studies, finasteride tablets reduced serum PSA concentration by approximately 50% within six months of treatment. This decrease is predictable over the entire range of PSA values in patients with symptomatic BPH, although it may vary in individuals. For interpretation of serial PSAs in men taking finasteride tablets, a new PSA baseline should be established at least six months after starting treatment and PSA monitored periodically thereafter. Any confirmed increase from the lowest PSA value while on finasteride tablets may signal the presence of prostate cancer and should be evaluated, even if PSA levels are still within the normal range for men not taking a 5α-reductase inhibitor. Non-compliance with finasteride tablets therapy may also affect PSA test results. To interpret an isolated PSA value in patients treated with finasteride tablets for six months or more, PSA values should be doubled for comparison with normal ranges in untreated men. These adjustments preserve the utility of PSA to detect prostate cancer in men treated with finasteride tablets. Finasteride tablets may also cause decreases in serum PSA in the presence of prostate cancer. The ratio of free to total PSA (percent free PSA) remains constant even under the influence of finasteride tablets. If clinicians elect to use percent free PSA as an aid in the detection of prostate cancer in men undergoing finasteride therapy, no adjustment to its value appears necessary.

5.2 Increased Risk of High-Grade Prostate Cancer Men aged 55 and over with a normal digital rectal examination and PSA ≤3.0 ng/mL at baseline taking finasteride 5 mg/day in the 7-year Prostate Cancer Prevention Trial (PCPT) had an increased risk of Gleason score 8 to 10 prostate cancer (finasteride 1.8% vs placebo 1.1%). [ See Indications and Usage (1.3) and Adverse Reactions (6.1) . ] Similar results were observed in a 4-year placebo-controlled clinical trial with another 5α-reductase inhibitor (dutasteride, AVODART) (1% dutasteride vs 0.5% placebo). 5α-reductase inhibitors may increase the risk of development of high-grade prostate cancer. Whether the effect of 5α-reductase inhibitors to reduce prostate volume, or study-related factors, impacted the results of these studies has not been established.

5.3 Exposure of Females- Risk to Male Fetus Finasteride tablets is contraindicated in pregnant females and in females who may potentially be pregnant and not indicated for use in females. Based on animal studies and the mechanism of action, finasteride tablets may cause abnormal development of external genitalia in a male fetus if administered to a pregnant female. Females who are pregnant or may potentially be pregnant should not handle crushed or broken finasteride tablets. Finasteride tablets are coated and will prevent contact with the active ingredient during normal handling, provided that the tablets have not been broken or crushed. If a pregnant female comes in contact with crushed or broken finasteride tablets, the contact area should be washed immediately with soap and water. [See Contraindications (4), Use in Specific Populations (8.1), Clinical Pharmacology (12.1 and 12.3), and How Supplied/Storage and Handling (16).]

5.4 Pediatric Patients and Females Finasteride tablets is not indicated for use in pediatric patients [ see Use in Specific Populations (8.4) and Clinical Pharmacology (12.3) ] or females [ see also Warnings and Precautions (5.3) , Use in Specific Populations (8.1) , Clinical Pharmacology (12.3) , and How Supplied/ Storage and Handling (16) ].

5.5 Effect on Semen Characteristics Treatment with finasteride tablets for 24 weeks to evaluate semen parameters in healthy male volunteers revealed no clinically meaningful effects on sperm concentration, mobility, morphology, or pH. A 0.6 mL (22.1%) median decrease in ejaculate volume with a concomitant reduction in total sperm per ejaculate was observed. These parameters remained within the normal range and were reversible upon discontinuation of therapy with an average time to return to baseline of 84 weeks.

5.6 Consideration of Other Urological Conditions Prior to initiating treatment with finasteride tablets, consideration should be given to other urological conditions that may cause similar symptoms. In addition, prostate cancer and BPH may coexist. Patients with large residual urinary volume and/or severely diminished urinary flow should be carefully monitored for obstructive uropathy. These patients may not be candidates for finasteride therapy.