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Minoxidil USP (38304-91-5)

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What is Minoxidil

Minoxidil (2,4-diamino-6-piperidinopyrimidine 3-oxide),  a pyrimidine N-oxide, often known as Rogaine, is a drug used to treat high blood pressure and hair loss in males and females. It is available as a prescription-only generic drug in the form of oral tablets, as well as over-the-counter medicine as a topical liquid or foam. When it comes to hypertension, minoxidil is often reserved for individuals who have failed to react to at least two medications plus a diuretic.  It acts as a potent direct-acting peripheral vasodilator that reduces peripheral resistance and produces a fall in blood pressure.

Macsen Laboratories is the supplier of high-quality Minoxidil USP.
Name of Product Minoxidil USP
IUPAC Name 3-hydroxy-2-imino-6-piperidin-1-ylpyrimidin-4-amine
Synonyms Rogaine, Loniten, Regaine
CAS No 38304-91-5
Molecular Formula C9H15N5O
Molecular Weight 209.25
Pubchem CID 4201
Pubchem SID 463577160


SR. No Criteria Limit/Specification
1 Appearance (Color) White to off-white crystalline powder
2 Solubility Soluble in alcohol and in propylene glycol, sparingly soluble in methanol, slightly soluble in water. Practically insoluble in chloroform, acetone, ethyl acetate and in hexane
3 Identification
By IR Absorption spectrum
The infrared absorption spectrum of the sample should be concordant with the IR absorption spectrum of Minoxidil working standard
4 Assay by HPLC (on dried basis) NLT 97.0% and NMT 103.0%
5 Impurities
A. Residue on ignition
B. Organic Impurities by HPLC Total Impurities

NMT 0.5%
NMT 1.5%
6 Loss on drying NMT 0.5%
7 Residual solvents by GC-HS

Not more than 3000 ppm
Not more than 1000 ppm

How does Minoxidil work

The exact method through which minoxidil stimulates hair growth is unknown. Minoxidil is an adenosine 5′-triphosphate-sensitive potassium channel opener that causes cell membrane hyperpolarization. Theoretically, it allows more oxygen, blood, and nutrients to reach the follicles by enlarging blood vessels and opening potassium channels. It also has a nitric oxide moiety, which might make it a nitric oxide agonist. This may cause telogen-phase follicles to shed, only to be replaced by stronger hairs in the anagen phase. 

Adenosine, which activates intracellular signal transduction via both adenosine A1 receptors and two subtypes of adenosine A2 receptors (A2A and A2B receptors), mediates the impact of minoxidil. Minoxidil selectively binds to SUR2 and functions as an activator of the Kir6/SUR2 channel. It activates the uncoupled sulfonylurea receptor on the plasma membrane of dermal papilla cells, which increases cell growth factors such as VEGF, HGF, and IGF-1 and potentiates HGF and IGF-1 activities.

When administered as a vasodilator, Minoxidil works by opening potassium channels in vascular smooth muscle cells that are sensitive to adenosine triphosphate thus relaxing and enlarging certain small blood vessels in your body so that blood flows through them more easily. This helps to reduce your blood pressure.

Uses of Minoxidil

  • The most common use of Minoxidil is in topical therapy for hair loss.
  • It is useful in promoting hair growth in both men and women with androgenic alopecia.
  • For the continuous support of existing hair follicles and the maintenance of any experienced hair regrowth, minoxidil must be used consistently.
  • It is also used for the treatment of severe hypertension.

Side Effects of Minoxidil

  • Minoxidil is typically well accepted when administered topically, however inflammation of the eye, itching, redness, or irritation in the treated region, and undesired hair growth elsewhere on the body are all frequent adverse effects.
  • Hair loss/alopecia has been observed to worsen.
  • Rashes, itching, breathing difficulties, swelling of the mouth, face, lips, or tongue, chest discomfort, dizziness, fainting, tachycardia, headache, abrupt and unexplained weight gain, or swelling of the hands and feet are all possible adverse effects.
  • Erectile dysfunction, depression, anxiety, diminished libido, and skin diseases are all rare adverse effects.
  • The negative effect of minoxidil therapy is temporary hair loss, which is referred to as “shedding.”


Q. Is Minoxidil safe?

Minoxidil is a medicine for hair loss in men and women that has been approved by Health Canada and the US FDA. Topical preparations containing 2% and 5% of the medication are available. This OTC medication is regarded safe, however it should be used with caution.

Q. How long does Minoxidil take to work?

In general, it takes about 8 weeks of constant use to notice effects with minoxidil. After four months, you should notice a decrease in hair loss and an increase in hair growth.

Q. What is the effectiveness of Minoxidil for women?

Minoxidil is the only drug which is FDA-approved to treat female pattern baldness. It slows down or stops hair lossby prolonging the growth phase of the hair follicles.

Q. Does Minoxidil work for beard?

The short answer is yes, but more studies are needed for proper evidence.

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