It is safe to say that both topical finasteride and oral finasteride are extremely safe medication and does not interact with any other medications to affect the body negatively.

Finasteride has been used from 1992, with many long term studies where side effects were extensively researched,

The beneficial effect of finasteride in stopping hair loss from male pattern baldness was an accidental discovery since finasteride was first used to treat benign prostate enlargement.

Literally a hair raising experience when this good side effect of finasteride was seen in patients treated for benign prostate enlargement. ;)

Topical Finasteride or oral finasteride both are safe to take, and both do not affect liver, kidneys or the heart. No internal organs will be affected by using topical or oral finasteride.

The amount of topical finasteride which is always mixed with Minoxidil is even less than oral finasteride. It is .1 Mg. Minoxidil or Rogaine(brand name) is extremely beneficial to hair growth since it nourishes the root system with enhanced blood supply.

Minoxidil which is a topical application to the scalp has been used for long without any side effects as well. ​

Topical Finasteride and Oral Finasteride Finasteride – Drug Interactions

Finasteride has no drug interactions of clinical importance. It does not affect the cytochrome P450-linked drug-metabolizing enzyme system. ​

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.​

Cytochrome P450 enzymes are essential for the metabolism of many medications.

Also crucial for production of cholesterol, steroids, prostacyclins, and thromboxane A2. are necessary for the detoxification of foreign chemicals and the metabolism of drugs. ​

CYP450 enzymes are so named because they are bound to membranes within a cell (cyto) and contain a heme pigment (chrome and P) that absorbs light at a wavelength of 450 nm when exposed to carbon monoxide. There are more than 50 CYP450 enzymes, but the CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 enzymes metabolize 90 percent of drugs. These enzymes are predominantly expressed in the liver, but they also occur in the small intestine (reducing drug bioavailability), lungs, placenta, and kidneys.​

Studies with major drugs and finasteride

While specific interaction studies are not done, finasteride 1 mg dose or more was used concomitantly in clinical studies with acetaminophen, acetylsalicylic acid, a-blockers, analgesics, angiotensin converting enzyme(ACE) inhibitors, anticonvulsants, benzodiazepines, beta blockers, calcium -channel blockers, cardiac nitrates, diuretics, H2 antagonists, HMG- CoA reductase inhibitors, prostaglandin synthetase inhibitors, quinolone anti-infectives without evidence of clinically significant adverse interactions. ​

Finasteride rapidly reduces serum DHT concentration, suppressing 65% within 24 hours of oral dosing with a 1-mg tablet. Mean circulating levels of testosterone and estradiol were increased by approximately 15% as compared to baseline, while maintaining normal range.​

Finasteride and HPT axis

No clinically meaningful changes in luteinizing hormone(LH), follicle-stimulating hormone(FSH) or prolactin was found. ​

In healthy volunteers, treatment with finasteride did not alter the response of LH and FSH to Gonadotropin-releasing hormone(GRH) indicating that the hypothalamic-pituitary-testicular axis was not affected. ​

Circulating levels of cortisol, thyroid stimulating hormone, or thyroxine had a neutral effect from finasteride. ​

Neither did finasteride affect the plasma lipid profile(eg., total cholesterol, low-density lipoproteins, high-density lipoproteins, triglycerides or bone mineral density. ​

Bone mineral density not being impacted by finasteride is also important from TRT perspective. Testosterone helps improve bone mineral density and long term testosterone patients are prescribed finasteride to prevent hair loss from DHT conversion. ​

Finasteride and liver abnormalities

Since Finasteride is metabolized mainly in the liver, caution is necessary while treating patients who are suffering from liver complications. ​

Finasteride and fertility

No effect from finasteride on fertility was found in sexually mature male rabbits treated with 4344 times the human dose of finasteride for up to 12 weeks. ​

No effect on fertility, sperm count or ejaculate volume was seen. ​

No significant effect on fertility seen from finasteride after 6 or 12 weeks on mature male rats treated with 488 times the human exposure(80 mg/kg/day). ​

However, when finasteride was continued for up to 24 or 30 weeks, there was a decrease in fertility, fecundity and significant decrease in weights of the seminal vesicles and prostate. ​

All these effects were reversible within 6 weeks of discontinuation of treatment. ​

No effects from finasteride seen on testes or on mating performance in rats or rabbits. ​

Contraindications of Topical Finasteride and Oral Finasteride

Pregnant women should never come into contact with finasteride tablets, esp. If splitting a 5 mg tablet. Finasteride from the powder or fragments can be absorbed through skin and can cause genital abnormalities in a male fetus due to lack of DHT. ​

So to conclude, finasteride is an absolute miracle drug for those suffering from male pattern baldness, with no significant side effects or drug reactions. It has been prescribed to millions of patients to treat hair loss safely over decades. ​

Science&Humans’s regimen of quarterly doctor consults will make sure that all such concerns are addressed. Finasteride dosage and frequency will be adjusted based on the individual patient’s needs. Topical finasteride is also custom compounded with minoxidil to suit individual needs and sensitivities. ​