Finasteride

G04C - Drugs used in benign prostatic hypertrophy ATC G04CB01 Small molecule approved 1992 Oral Natural product

JFDA label: Prostacare Tab

Mechanism of Action

Inhibitor of 3-oxo-5-alpha-steroid 4-dehydrogenase 2 — Steroid 5-alpha-reductase 2 inhibitor

Target	Action	Gene / class
3-oxo-5-alpha-steroid 4-dehydrogenase 2 efficacy	INHIBITOR	SRD5A2

Indications

Approved

Androgenetic alopecia (Propecia)
Benign prostatic hyperplasia (Proscar)

Off-label

Female hirsutism (idiopathic)
Female hirsutism (related to polycystic ovary syndrome)

Contraindications

Source: Lexicomp · Curated

Hypersensitivity to finasteride or any component of the formulation Absolute
Pregnancy or women of childbearing potential (teratogenic — feminises male foetus) Absolute
pregnancy or women of childbearing potential Absolute

Adverse Reactions

Very Common >10%Common 1–10%Uncommon 0.1–1% Rare 0.01–0.1%Very Rare <0.01%Not Known

Cardiac disorders (2)

Very Common Orthostatic hypotension

Common Edema

Nervous system disorders (2)

Very Common Dizziness

Common Drowsiness

Renal and urinary disorders (4)

Very Common ejaculatory disorder · Impotence

Common breast tenderness · Decreased ejaculate volume

Metabolism and nutrition disorders (2)

Very Common Decreased libido

Common Gynecomastia

Skin and subcutaneous tissue disorders (1)

Common Skin rash

Other (1)

Not Known “Combination therapy” refers to finasteride and doxazosin

Respiratory, thoracic and mediastinal disorders (2)

Common Dyspnea · rhinitis

Dosing

Source: Lexicomp

Benign prostatic hyperplasia (Proscar): Males: Oral: 5 mg once daily (either as a single agent or in combination with doxazosin); early responses may occur although 6 months of treatment is usually needed to assess benefit. Male pattern baldness (Propecia): Males: Oral: 1 mg once daily; may take 3 months or longer of daily use for observed benefit; continued use is recommended to sustain benefit. Female hirsutism, idiopathic (off-label use): Females: Oral: 5 mg once daily (Beigi, 2004; Lumachi, 2003; Moghetti, 2000) or 2.5 mg once daily (Tartagni 2004). Female hirsutism, related to polycystic ovary syndrome (off-label use): Females: Oral: 5 mg once daily (Beigi 2004; Moghetti 2000) or 2.5 mg once daily (Tartagni 2004).

Refer to adult dosing.

No dosage adjustment is necessary.

There are no dosage adjustments provided in the manufacturer’s labeling. Use with caution (finasteride is metabolized extensively in the liver)

Warnings & Precautions

Source: Lexicomp

Diminished urinary flow

Carefully monitor patients with a large residual urinary volume or severely diminished urinary flow for obstructive uropathy; these patients may not be candidates for finasteride therapy.

Hepatic impairment

Use with caution in patients with hepatic impairment; finasteride is extensively metabolized in the liver.

Prostate cancer

When compared to placebo, 5-alpha-reductase inhibitors (5-ARIs) have been associated with an increase in the incidence of high-grade prostate cancers; 5-ARIs are not approved in the US or Canada for the prevention of prostate cancer. Special handling:

Females/pregnancy

Active ingredient of crushed or broken tablets can be absorbed through the skin; unbroken tablets are coated which prevents contact with the active ingredient during normal handling. Pregnant females should avoid contact with crushed or broken tablets; finasteride may negatively impact fetal development. Other warnings/precautions:

Appropriate use

Other urological diseases (including prostate cancer) should be ruled out before initiating (in BPH management). Not indicated for use in pediatric patients.

Duration of therapy

For BPH, a minimum of 6 months of treatment may be necessary to determine whether an individual will respond to finasteride; for male pattern hair loss, daily use for 3 months or longer may be required before benefit is observed (withdrawal of treatment leads to reversal of hair growth effect within 12 months).

PSA monitoring

Reduces prostate specific antigen (PSA) concentration by ~50% within 6 months of treatment. To interpret serial PSAs, a new PSA baseline should be established ≥6 months after treatment initiation and PSA monitored periodically thereafter. A confirmed PSA increase while on this medication, even if within normal limits, may be associated with an increased risk for prostate cancer and should be evaluated. Finasteride does not interfere with free PSA levels.

Pregnancy & Lactation

Pregnancy

FDA category X Teratogenic Contraindicated

Contraindicated

Crushed tablets should not be handled by women who are or may be pregnant. Male partners on finasteride: semen transfer negligible but condom use recommended

Lactation

Contraindicated

Use is contraindicated in women of childbearing potential. It is not known if finasteride is excreted in breast milk.

Monitoring

Clinical pearl	To interpret serial PSAs, establish a new PSA baseline ≥6 months after treatment initiation and monitor PSA periodically thereafter. Objective and subjective signs of relief of benign prostatic hyperplasia, including improvement in urinary flow, reduction in symptoms of urgency, and relief of difficulty in micturition.

Chemistry & Properties

Formula	C23H36N2O2
Molecular weight	372.55 g/mol
IUPAC name	(1S,3aS,3bS,5aR,9aR,9bS,11aS)-N-tert-butyl-9a,11a-dimethyl-7-oxo-1,2,3,3a,3b,4,5,5a,6,9b,10,11-dodecahydroindeno[5,4-f]quinoline-1-carboxamide
CAS	98319-26-7
PubChem CID	57363
InChIKey	`DBEPLOCGEIEOCV-WSBQPABSSA-N`
logP	3.81 (XLogP 3.0)
Polar surface area	58.2 Å²
H-bond acceptors / donors	2 / 2
Drug-likeness (QED)	0.74
Lipinski violations	0

SMILES

CC(C)(C)NC(=O)[C@H]1CC[C@H]2[C@@H]3CC[C@H]4NC(=O)C=C[C@]4(C)[C@H]3CC[C@]12C

Biology & Pharmacokinetics

Pharmacokinetics predicted

Bioavailability	70.0%
Half-life	0.428 h
Volume of distribution	0.912 L/kg
Protein binding	87.2%
BBB penetrant	No

Enzyme interactions

Enzyme	Role	Detail
CYP2B6	Inhibitor	—
CYP2C19	Inhibitor	IC₅₀ 1.0 µM
CYP2C9	Inhibitor	IC₅₀ 2.0000000000000004 µM
CYP3A4	Inhibitor	—
CYP3A4	Substrate	—

Receptor binding (top 1)

Target	Action	Affinity
steroid 5 alpha-reductase 2 (SRD5A2)	Inhibitor	pIC50 7.8

Transporters

BCRP (Inhibitor)BSEP (Inhibitor)BSEP (Inhibitor)MRP1 (Inhibitor)MRP2 (Inhibitor)MRP3 (Inhibitor)MRP4 (Inhibitor)OATP1B1 (Inhibitor)OATP1B3 (Inhibitor)P-gp (Inhibitor)P-gp (Substrate)

Drug–drug interactions (22, DDInter)

Interacting drug	Severity	Management
Abametapir (topical)	moderate
Diltiazem	moderate
Duvelisib	moderate
Fluconazole	moderate
Fluvoxamine	moderate
Fostamatinib	moderate
Ginseng	moderate
Itraconazole	moderate
Larotrectinib	moderate
Lefamulin	moderate
Nefazodone	moderate
Nelfinavir	moderate
Saquinavir	moderate
Selpercatinib	moderate
Sirolimus	moderate
Somapacitan	moderate
Somatotropin	moderate
Somatrem	moderate
Tacrolimus	moderate
Temsirolimus	moderate
Voriconazole	moderate
Terazosin	minor

Registered Products (8)

Brand	Form / strength	Pack	Agent	Citizen (JOD)
FINHET 5	Tablet 5.000 mg	30 tab	Omicron Pharma	6.870
Prohair Tab	Tablet 1 mg	30 tab pack varies	Hayat Pharmaceutical Industries CO.PLC/JORDAN	8.000
Prostacare Tab	Tablet 5 mg	30 tab pack varies	Hayat Pharmaceutical Industries CO.PLC/JORDAN	8.830
PROSCAR Film Coated Tablets	Film-Coated Tablet 5 mg	28 tab	Adatco Drug Store	9.160
Prohair Tab	Tablet 1 mg	50 tab pack varies	Hayat Pharmaceutical Industries CO.PLC/JORDAN	13.330
Finjuve	Spray 2.275 mg/1 ml	1 Bottle with a pump attached (corresponding to 180 sprays) Cutaneous spray , solution + 1 separate	Hikma Pharmaceuticals Co.Ltd/Jordan	42.890
Prostacare Tab	Tablet 5 mg	510 tab pack varies	Hayat Pharmaceutical Industries CO.PLC/JORDAN	129.140
Prostacare Tab	Tablet 5 mg	1000 tab pack varies	Hayat Pharmaceutical Industries CO.PLC/JORDAN	250.180