Sulfapyridine, original UK spelling Sulphapyridine, is a sulfonamide

Sulfonamide (medicine)

Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...

 antibacterial. At one time it was commonly referred to as M&B.

Sulfapyridine is not prescribed for treatment in humans any more. However, it may be used to treat Linear IgA Disease

Linear IgA bullous dermatosis

Linear IgA bullous dermatosis is frequently associated with medication exposure, especially vancomycin, with men and women being equally affected. Linear IgA dermatosis is a rare immune-mediated blistering skin disease that may be divided into two types, chronic bullous disease of childhood and...

. It is a good antibacterial drug, but its water solubility

Solubility

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

 is very pH

PH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 dependent. Thus there is a risk of crystallization

Crystallization

Crystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...

 within the bladder

Bladder

Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...

 or urethra

Urethra

In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

, which could lead to pain or blockage.

Discovered by May & Baker

May & Baker

May & Baker was a British chemical company.It was started by Mr. May and Mr. Baker in Wandsworth, London in 1851. They initially specialized in the manufacture of chemicals derived from Mercury and Bismuth...

 Ltd and logged in their Test Book on 2 November 1937 under Code No M&B693. Successfully used to treat Winston Churchill's bacterial pneumonia in 1942. In a subsequent radio broadcast he said "This admirable M&B from which I did not suffer any inconvenience, was used at the earliest moment and, after a week's fever, the intruders were repulsed."
In 1944 M&B693 also saved Nero, the Royal Circus lion, from pneumonia.[Glasgow Evening News January 1944.]

The drug sulfasalazine is structurally one molecule of mesalamine linked to one molecule of Sulfapyridine with an azo bond.