Phenylbutazone

Toxicity

Oral, LD50 = 238 mg/kg (mouse); Oral, LD50 = 781 mg/kg (rabbit); Oral, LD50 = 245 mg/kg (rat); Oral, LD50 = 375 mg/kg (rat)

Description

Phenylbutazone, one of the earliest NSAIDs introduced, is now indicated for the symptomatic relief of rheumatoid arthritis, osteoarthritis, psoriatic arthritis, ankylosing spondylitis, gout, and acute superficial thrombophlebitis. The gastrointestinal and bone marrow toxicity observed in its early use have been greatly reduced by lower dosage (300 mg/d). Nevertheless, it is used primarily where other drugs have failed and then only for short-term therapy. The drug has a long serum half-life of about 100 h. It is a moderately active cyclooxygenase inhibitor and it suppresses both spontaneous and chemotactic motility of neutrophils. In addition to the serious gastrointestinal and hematological adverse effects, sodium and water retention, rash, vertigo, and dermatitis are observed.

Chemical properties

Off-Whtie Solid

Originator

Butazolidin, Geigy ,US,1952

The Uses of Phenylbutazone

Phenylbutazone, a nonsteroidal anti-inflammatory drug, is an efficient reducing cofactor for the peroxidase activity of COX. Phenylbutazone-dependent inactivation of COX and prostacyclin synthase is markedly increased in the presence of 100 μM hydrogen peroxide with half-maximal effects at Phenylbutazone concentrations of 100 and 25 μM for COX and prostacyclin synthase, respectively.

The Uses of Phenylbutazone

A non-steroidal anti-inflammatory compound. An inhibitor of cyclooxygenase that is also a substrate for peroxidation by cyclooxygenase

The Uses of Phenylbutazone

For the treatment of backache and ankylosing spondylitis

The Uses of Phenylbutazone

An inhibitor of Cox.

Indications

For the treatment of backache and ankylosing spondylitis

Background

A drug that has anti-inflammatory, antipyretic, and analgesic activities. It is especially effective in the treatment of ankylosing spondylitis. It also is useful in rheumatoid arthritis and Reiter's syndrome (investigational indication). Although phenylbutazone is effective in gouty arthritis, risk/benefit considerations indicate that this drug should not be employed for this disease. (From AMA Drug Evaluations Annual, 1994, p1822)

What are the applications of Application

Phenylbutazone is an inhibitor of Cox

Definition

ChEBI: Phenylbutazone is a member of the class of pyrazolidines that is 1,2-diphenylpyrazolidine-3,5-dione carrying a butyl group at the 4-position. It has a role as a non-narcotic analgesic, a non-steroidal anti-inflammatory drug, an antirheumatic drug, a peripheral nervous system drug, a metabolite and an EC 1.1.1.184 [carbonyl reductase (NADPH)] inhibitor.

Manufacturing Process

7.6 parts of sodium are dissolved in 190 parts by volume of absolute alcohol; 65 parts of diethyl-n-butyl malonate and 65 parts of hydrazobenzene are added. The alcohol is slowly distilled off and the reaction mixture heated for 12 hours at a bath temperature of 150°C and finally in vacuo, until no more alcohol comes off.
The product is dissolved in water, clarified with a little animal charcoal and 15% hydrochloric acid is slowly added until an acid reaction to Congo red paper is produced. 1,2-Diphenyl-3,5-dioxo-4-n-butyl-pyrazolidine separates as an oil, which rapidly become crystalline. It crystallizes from alcohol as colorless needles with a MP of 105°C.

brand name

Azolid (Sanofi Aventis); Butazolidin (Novartis);Algesin;Algirreudin;Algoverine;Alka butazolidin;Alkabutazone;Alka-phenylbutazone;Alka-sterazolidin;Anarthral;Apophenylbutazone;Apo-phenylbutazone;Arteopan;Arthirikin;Artibrin;Artrisin;Artrodesmol extra;Bizolin 20;Bizolin 700;Butacal;Butacol;Butadilat;Butadin;Butadyne;Butafenil;Butagros;Butakvertin;Butaparin;Butaphen;Buta-phen;Butarex;Butartiril;Butatril;Butazolidin alka;Butazolidina;Butial;Butinol;Butiwas;Buto beta;Butoroid cream;Butrex;Carudol;Celestalgon;Celestazone;Colfezone;Corbuvit;Dartranol;Debutazon;Delta-butazolidin;Delta-demoplas;Delta-myogit;Delta-tomanol;Deltawaukobuzon;Dephimixn;Dexa tomanol;Dexa-attritin;Dexa-escopyrin;Dexamed;Dexatrzona;Dibuzon;Direstop;Ditrone;Doctofril;Dolosin dexa;Dolpirina;Ectobutazone;Ethibute;Exraheudon;Exrheudon;F 650;Fenibutina;Flebosil;Glycyl;Hepabuzon;Inflazone;Intrabuzone;Mammyl;Megazone;Mepha-butazone;Mepropyrin;Mi 540;Naupax;Neuro-demoplas;Neuzoline m;Novobutazone;Oluprin;Oppazoen;Osadrinim;Parazolidin;Parzolidon;Pasirheuman;Penetradol;Phenbuff;Phenbutazone;Phenylarthrite;Phenylbetazone;Phenylon plus;Phlebolan;Pirabutil;Pirarreumol-b;Pirarreumol-p;Prebutex;Precirhemin;Prednirheumin;Proxyfezone;Proydynam;Pyrbutal;Ranocor;Reopin;Reumilene;Rheopyrin;Rheosolon;Rheumanoln;Rheumaphen;Rheumycalm;Salzone;Servizolidin;Sigma-elmedal;Sintobutina;Stabilat;Tevocodyn;Tibutazone;Ticinil calcio;Ticinil calico;Trabit;Zolapelin;Zolidinium.

Therapeutic Function

Antiinflammatory, Antiarthritic

World Health Organization (WHO)

Phenylbutazone, a pyrazolone derivative with anti-inflammatory, analgesic and antipyretic activity, was introduced in 1949 for the treatment of rheumatic disorders. Its use was subsequently associated with serious and sometimes fatal adverse reactions, notably cases of aplastic anaemia and agranulocytosis. Many national drug regulatory authorities consider that more recently introduced drugs offer a safer alternative for most, if not all, patients requiring anti-inflammatory agents. Phenylbutazone has thus been either withdrawn at the national level or retained with rigorously restricted indications for patients unresponsive to other therapy. These restrictions also apply, in general, to combination products containing phenylbutazone.

General Description

Odorless white or off-white crystalline powder. Tasteless at first, but slightly bitter aftertaste. pH (aqueous solution) 8.2.

Air & Water Reactions

Phenylbutazone is relatively stable at ambient temperatures. Aqueous decomposition of Phenylbutazone occurs by hydrolysis and oxidation. Insoluble in water.

Reactivity Profile

Phenylbutazone is incompatible with strong oxidizers, strong acids and strong bases. .

Fire Hazard

Flash point data for Phenylbutazone are not available; however, Phenylbutazone is probably combustible.

Biochem/physiol Actions

Phenylbutazone is a hepatotoxin and binds to plasma proteins. It is used to treat inflammation in horse. Phenylbutazone has potential to treat ankylosing spondylitis. It has therapeutic potential to treat myotonic dystrophy type 1 (DM1) by inducing muscle blind-like protein 1 (MBNL1) expression. It also favors the expression of muscle chloride channel in skeletal muscles.

Pharmacokinetics

Phenylbutazone is a synthetic, pyrazolone derivative. It is a nonhormonal anti-inflammatory, antipyretic compound useful in the management of inflammatory conditions. The apparent analgesic effect is probably related mainly to the compound's anti-inflammatory properties and arise from its ability to reduce production of prostaglandin H and prostacyclin. Prostaglandins act on a variety of cells such as vascular smooth muscle cells causing constriction or dilation, on platelets causing aggregation or disaggregation and on spinal neurons causing pain. Prostacylcin causes vascular constriction platelet disaggregation

Clinical Use

Phenylbutazone is a nonsteroidal anti-inflammatory drug used for the acute treatment of ankylosing spondylitis, chronic polyarthritis, and gout. Because of severe side effects including disturbances of the hematopoietic system like agranulocytosis and aplastic anemia the use is limited to conditions in which other nonsteroidal antiinflammatory drugs do not show sufficient efficacy. Phenylbutazone is given as oral, rectal, intramuscular or topical formulation (up to 600 mg/d initial dose, up to 400 mg/d maintenance dose). The peak plasma concentration is reached 2 h after oral application. Phenylbutazone is bound to 98% to plasma protein. Oxyphenbutazone is formed as an active metabolite of phenylbutazone.

Safety Profile

Suspected human carcinogen producing leukemia. A human poison by parenteral route. An experimental poison by ingestion, intraperitoneal, subcutaneous, intravenous, and intramuscular routes. Human systemic effects by ingestion and possibly other routes: fever, blood pressure increase, other unspecified vascular effects, damage to kidney tubules and glomeruli, decreased urine volume, blood in the urine, reduction in the number of whte blood cells, and agranulocytosis. Experimental teratogenic and reproductive effects. Human mutation data reported. An eye irritant. An antiinflammatory agent. When heated to decomposition it emits toxic fumes of NOx

Synthesis

Phenylbutazone, 4-butyl-1,2-diphenyl-3,5-pyrazolidinedione (3.2.6), is synthesized in a single stage by reacting hydrazobenzol with butylmalonic ester [68,69].

Veterinary Drugs and Treatments

One manufacturer lists the following as the indications for phenylbutazone: “For the relief of inflammatory conditions associated with the musculoskeletal system in dogs and horses.” (Package Insert; Butazolidin?—Coopers). It has been used primarily for the treatment of lameness in horses and, occasionally, as an analgesic/ antiinflammatory, antipyretic in dogs, cattle, and swine.

Metabolism

Not Available

Purification Methods

Crystallise the dione from EtOH. Its pK2 3 is 4.52 (in H2O), 4.89 (in 50% aqueous EtOH) and 5.25 (80% 2-methoxyethanol). It complexes with Hg2+, Cd2+ and Zn2+. It has UV with max at 239.5nm in MeOH+50% aqueous HClO4 and 264nm in aqueous 0.1N NaOH. [Beilstein 24 III/IV 1123.]