indication

For the treatment of backache and ankylosing spondylitis

pharmacology

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

mechanism of action

Phenylbutazone binds to and inactivates prostaglandin H synthase and prostacyclin synthase through peroxide (H2O2) mediated deactivation. The reduced production of prostaglandin leads to reduced inflammation of the surrounding tissues.

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)

drug interactions

Acenocoumarol: The NSAID, phenylbutazone, may increase the anticoagulant effect of acenocoumarol.

Acetohexamide: Phenylbutazone may increase the effect of acetohexamide.

Anisindione: The NSAID, phenylbutazone, may increase the anticoagulant effect of anisindione.

Chlorpropamide: Phenylbutazone increases the effect of the hypoglycemic agent

Dicumarol: The NSAID, phenylbutazone, may increase the anticoagulant effect of dicumarol.

Ethotoin: The NSAID, phenylbutazone, may increase the hydantoin effect of ethotoin.

Fosphenytoin: The NSAID, phenylbutazone, may increase the hydantoin effect of fosphenytoin.

Gliclazide: Phenylbutazone increases the effect of the hypoglycemic agent

Glipizide: Phenylbutazone increases the effect of the hypoglycemic agent

Glisoxepide: Phenylbutazone increases the effect of the hypoglycemic agent

Glyburide: Phenylbutazone increases the effect of the hypoglycemic agent

Glycodiazine: Phenylbutazone increases the effect of the hypoglycemic agent

Lithium: The NSAID, phenylbutazone, may decrease the renal excretion of lithium. Increased risk of lithium toxicity.

Mephenytoin: The NSAID, phenylbutazone, may increase the hydantoin effect of mephenytoin.

Methotrexate: The NSAID, phenylbutazone, may decrease the renal excretion of methotrexate. Increased risk of methotrexate toxicity.

Phenytoin: The NSAID, phenylbutazone, may increase the therapeutic and adverse effects of phenytoin.

Tolazamide: Phenylbutazone increases the effect of the hypoglycemic agent

Tolbutamide: Phenylbutazone increases the effect of the hypoglycemic agent

Warfarin: The NSAID, phenylbutazone, may increase the anticoagulant effect of warfarin.