Finasteride Side Effects

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Short fact about hair growth and hair loss

  • An adult has about 100,000 to 150,000 hairs and loses up to 100 hairs a day.
  • Hair is composed of two different structures the hair follicle which resides in the skin, and second, the shaft, which is visible above the scalp.
  • Hair growth has three stages of growth and shedding: anagen phase, the catagen phase and telogen phase.
  • During intrauterine life, approximately 5 million hair follicles are developed on the body.
  • A developing foetus has all its hair follicles formed by week 22.
  • No follicles are formed after birth.

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The structure of hair

Hair plays a vital role in the appearance of both men and women and also helps to transmit sensory information and to create gender identification.
Hair grows everywhere on the human skin except on the palms and the soles, but many hairs are so fine they are virtually invisible.
A total number of 5 million hair follicles are developed during the intrauterine life. One million of the follicles are present on the head, and one hundred thousand of those follicles residing on the scalp. This is the largest number of hair follicles a human will ever have. No more new hair follicles will be generated during the course of our lives.
The hair is composed of two different structures:

  • the hair follicle which resides in the skin;
  • the shaft, which is visible above the scalp.

The hair follicle is a tunnel-like segment of the epidermis and it extends down into the dermis. Its structure contains several layers, each layer having a separate function.

  • Papilla: contains capillaries or tiny blood vessels that nourish the cells.
  • The bulb: represents the living part of the hair; the cells of the bulb divide every 23 to 72 hours, remarkably faster than any other cell in the body.
  • Two sheaths, an inner and outer sheath: surround the follicle and also protect and form the hair shaft. The inner sheath follows the hair shaft and ends below the opening of a sebaceous (oil) gland, and sometimes an apocrine gland, while the outer sheath continues all way up to gland.

The hair shaft is composed of a hard protein called keratin that is produced in hair follicles in the outer layer of skin. Keratin is a water-insoluble protein, so it ensures the impermeability and protection of the hair.
The hair shaft is made of three layers:

  • Medulla (the inner layer);
  • Cortex (the second layer): it makes up most of the hair shaft, being the thickest layer of the hair shaft. The cortex contains melanin, the pigment that gives hair its colour. There are four basic colours of the hair: black, brown, red and yellow. With age, the cells responsible for melanin production, no longer produce melanin. Therefore, the hair becomes grey or white. Another important component of the cortex is represented by the proteins which expressed the shape of the hair, curly or straight.
  • Cuticle (the outer layer); it represents the outermost part of the hair shaft. It represents a transparent layer of overlapping cells. Over time, the cuticle will naturally break or become porous. Sebum or softeners like olive oil will keep the hair’s cuticle pliable and conditioned and protected.


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The hair growth phases

The hair has three stages of growth and shedding:

  • Anagen phase;
  • Catagen phase:
  • Telogen phase.

Anagen phase

Anagen phase represents the active phase of hair growth and it lasts about three to five years. During this phase, a new hair is formed and pushes the club hair (a hair that has stopped growing or is no longer in the anagen phase) up the follicle and eventually out.
During this phase, the hair grows about 1 cm every 28 days. At any one time, approximately 85 to 90% of scalp follicles are in the anagen phase of hair growth.
Body hair has the same mechanism of growth with the scalp hair. However, body hair remains in the active phase for a short period (about 30 to 45 days). For this reason, body hair grows remarkably shorter than scalp hair.


The catagen phase represents the second part of a hair’s lifecycle and it is a transitional stage. This phase lasts for about two to three weeks. During this phase, growth stops, and the outer root sheath shrinks and attaches to the root of the hair. Once the hair bulb no longer has access to the blood supply, it begins to convert to keratin. During this keratinisation process, the hair bulb becomes shaped like a club.


Telogen phase is the third phase of the hair’s cycle, occurring after both the anagen phase and catagen phase. During this phase, the hair growth is ceased and the hair becomes fully keratinized. The dermal papilla enters a resting state and does not supply any nutrition to the hair, which is fully grown. Telogen is the resting phase and usually accounts for 6% to 8% of all hairs. This phase lasts for about 100 days for hairs on the scalp and longer for hairs on the eyebrow, eyelash, arm, and leg. During this phase, the hair follicle is completely at rest and the club hair is completely formed. Each day are shed about 25 to 100 telogen hairs. At the end of the telogen phase, the original hair falls out (exogenous phase) and is replaced by a new hair at the early growth stage.

Which are the risk factors for hair loss?

Hair loss has a significant effect on the social and psychologic well-being of both men and women of all ages.
The following factors may lead to the occurrence of hair loss:

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Treatment of hair loss

The most commonly used drugs for hair loss are:

  • Minoxidil (Rogaine): it is a topical solution that is applied to the scalp to stimulate hair follicles. It comes in 2% and 5% solutions and is applied once daily.
  • Finasteride (Propecia, Proscar): it is a pill that interferes with the production of a form of testosterone that is linked to baldness. This drug is not indicated to be used in females. Women who are or may become pregnant should not handle crushed or broken finasteride tablets when they are pregnant or may potentially be pregnant because of the possibility of absorption of finasteride and the subsequent potential risk to a male foetus.

What is Finasteride?

Finasteride is a prescription drug available as oral tablets. Finasteride can be found brand names Proscar (5 mg tablets) and Propecia (1 mg tablets).
Finasteride belongs to the class of drugs called 5 alpha-reductase inhibitors. The 5-alpha-reductase is an intracellular enzyme that converts testosterone to its active form, dihydrotestosterone (DHT). Dihydrotestosterone (DHT) is the main hormone responsible for androgenetic alopecia. This hormone causes scalp hair loss by inducing a change in the hair follicles on the scalp. Also, dihydrotestosterone leads to prostate enlargement.
Finasteride formulated as 1 mg tablets are indicated in the treatment of androgenic alopecia (men only) while Finasteride 5 mg tablets are used in the treatment of benign prostatic hyperplasia.


How does Finasteride work?

Finasteride is a competitive and specific inhibitor of type II 5α-reductase. Finasteride has no affinity for the androgen receptor and has no androgenic, anti-androgenic, oestrogenic, anti-oestrogenic, or progestational effects. Inhibition of this enzyme blocks the peripheral conversion of testosterone to the androgen DHT, resulting in significant decreases in serum and tissue DHT concentrations. Finasteride produces a rapid reduction in serum DHT concentration, reaching significant suppression within 24 hours of dosing.
Hair follicles contain type II 5α-reductase. In men with male pattern hair loss, the balding scalp contains miniaturised hair follicles and increased amounts of DHT. Administration of finasteride decreases scalp and serum DHT concentrations in these men. Men with a genetic deficiency of type II 5α-reductase do not suffer from male pattern hair loss. Finasteride inhibits a process responsible for miniaturisation of the scalp hair follicles, which can lead to a reversal of the balding process.

Pharmacokinetic profile of Finasteride

Compared with an intravenous interference dose, oral bioavailability of finasteride is approximately 80%. Oral bioavailability is not influenced by food. Maximum plasma concentration of finasteride is reached approximately two hours after administration and the absorption is complete after six to eight hours.
Finasteride is metabolized via cytochrome P450 3A4 system to two metabolites. The metabolites were found to possess only a small fraction of the 5-alpha-reductase inhibitory activity of finasteride.
The elimination rate of finasteride decreases somewhat with age. Mean terminal half-life is approximately 5-6 hours in men 18-60 years of age and 8 hours in elderly men (more than 70 years of age).
These findings are of no clinical significance and hence, a reduction in dosage in the elderly is not warranted.


What are the side effects of Finasteride? Is it safe for me?

Finasteride can cause side effects like any other drugs, although not everybody gets them. Some of the side effects are temporary and disappeared when treatment is stopped.

The following adverse reactions have been identified during post-approval use of Finasteride, they are reported voluntarily from a population of uncertain size and it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure:

  • Hypersensitivity Reaction: hypersensitivity reactions such as rash, pruritus, urticaria, and angioedema (including swelling of the lips, tongue, throat, and face);
  • Reproductive System: sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders; male infertility and/or poor seminal quality (normalization or improvement of seminal quality has been reported after discontinuation of finasteride); testicular pain.
  • Neoplasms: male breast cancer;
  • Breast disorders: breast tenderness and enlargement;
  • Nervous System/Psychiatric: depression

Stop taking the drug and talk to your doctor if you experience:

  • Symptoms of an allergic reaction: swelling of your lips, face, tongue and throat; difficulty swallowing; lumps under your skin (hives) and breathing difficulties.
  • Depression (feeling of severe sadness and unworthiness).

You should promptly report to your doctor any changes in your breast tissue such as lumps, pain, enlargement or nipple discharge as these may be signs of a serious condition, such as breast cancer.

Uncommon side effects (may affect up to 1 in 100 people) are the following:

  • Incapacity to have an erection (impotence);
  • Have less desire for having sex;
  • Problems with ejaculation, for example, a decrease in the amount of semen released during sex. This decrease in the amount of semen does not appear to affect normal sexual function.

Side effects with unknown frequency include:

  • breast tenderness and enlargement;
  • testicular pain;
  • infertility;
  • palpitations (heart is beating too hard or too fast);
  • increased hepatic enzymes;
  • persistent difficulty having an erection after discontinuation of treatment;
  • persistent decrease in sex drive after discontinuation of treatment;
  • persistent problems with ejaculation after discontinuation of treatment;
  • male infertility and/or poor quality of semen.

If any of these side effects gets serious, or if you notice any side effects not listed on patient information leaflet you should contact immediately your doctor or pharmacist.


Warning and precautions

Finasteride should never be taken by women or children. If a woman is exposed to Finasteride during pregnancy, birth defects can be met. Finasteride tablets should not be handled by a woman who is pregnant or may become pregnant.
Before taking Finasteride, tell to your doctor if you suffer or have been suffering from the following medical conditions:

  • allergy to finasteride;
  • liver disease;
  • prostate cancer;
  • a bladder muscle disorder;
  • urination problems;
  • an allergic reaction to a similar medicine called dutasteride (Avodart).


How should I take finasteride?

Finasteride tablets may be administered with or without meals.
The recommended dose of Finasteride is one tablet (1 mg) taken once daily.
In general, daily use for three months or more is necessary before benefit is observed. Continued use is recommended to sustain benefit, which should be re-evaluated periodically. Withdrawal of treatment leads to reversal of effect within 12 months.


How to prevent hair loss?

  • Limit the use of hair dryers or other devices that heat your hair like hot curlers, jot brushes and hair straighteners; constant heating and drying can lead to brittleness and fragility that can cause hair loss that would not have occurred otherwise.
  • Manage your stress; High level of testosterone represents one of the most common causes of hair loss. Because your stress levels could affect the levels of testosterone, it is very important to control your stress.
  • Eat healthy food. Foods rich in antioxidants and nutrients are helpful in reducing toxins and free radicals that contribute to oxidative stress in our bodies. Blueberries, green leafy foods, organic foods without pesticides and green tea are some of the many choices that will combat oxidative stress.
    Iron is an essential mineral that is known as heme iron in animal food sources and non-heme iron in plant sources. Too little iron can lead to anaemia which disrupts the supply of nutrients to your follicles, potentially increasing hair loss. Try to combine iron-rich foods with foods with plenty of vitamin C. Vitamin C helps in the good absorption of iron and contributes to the production of collagen. The collagen has the role of strengthening capillaries which supply the hair shafts.
    Another important vitamin for hair is biotin. Biotin is a vitamin B that is water soluble. The deficiency of biotin can cause your hair to become brittle and could accelerate hair loss. Foods rich in biotin include whole grains, liver, egg white, soy flour, walnuts and yeast
    Protein is essential for strong hair. A deficiency in protein can lead to dry and weak hair, and ultimately, hair loss. Adequate protein can help to provide the amino acids that strengthen hair. It is often included in shampoos, but it is protein from your diet that will help improve the condition of your hair and prevent hair loss if you eat it in large enough quantities. Get protein by eating seafood, poultry, milk, cheese, yoghurt, eggs, beans, pork tenderloin, soy, lean beef, and protein bars.


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  3. Springer K, Brown M, Stulberg DL. Common hair loss disorders. Am Fam Physician. 2003 Jul 1;68(1):93-102.
  8. Sudduth SL, Koronkowski MJ. Finasteride: the first 5 alpha-reductase inhibitors. Pharmacotherapy. 1993 Jul-Aug;13(4):309-25; discussion 325-9. Review. PubMed PMID: 7689728.
  9. Finasteride, Summary of product characteristics

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