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Flextra-650 (Acetaminophen / Phenyltoloxamine Citrate) - Description and Clinical Pharmacology


Each Tablet Contains:

Acetaminophen.......... 650 mg

Citrate           ............. 60 mg

Acetaminophen, 4'-hydroxyacetanilide, a slightly bitter, white, odorless, crystalline powder, is a non-opiate, non-salicylate analgesic and antipyretic. It has the following structural formula:


C8H2NO2            MW = 151.17

Phenyltoloxamine Citrate is a antihistamine having the chemical name N,N-dimethyl -2- (alpha-phenyl-o-tolyoxy) ethylamine dihydrogen citrate with the following chemical structure.

2. Phenyltoloxamine Citrate

N, N-dimethyl-2 (alpha phenyl-ortho-tolxy)-ethyl-amine citrate
C17H21NO - C5H8O7            MW = 447.48

Inactive Ingredients
Each tablet contains microcrystaline cellulose, sodium starch glycolate, and magnesium stearate. Contains FD and C Red No. 40 Aluminum Lake and Orange Lake Blend


The analgesic action of Acetaminophen involves peripheral influences, but the specific mechanism is as yet undetermined. Antipyretic activity is mediated through hypothalamic heat regulating centers. Acetaminophen inhibits prostaglandin synthetase. Therapeutic doses of Acetaminophen have negligible effects on the cardiovascular or respiratory system; however, toxic doses may cause circulatory failure and rapid shallow breathing.


The behavior of the individual components is described below.

Acetaminophen is rapidly absorbed from the gastrointestinal tract and is distributed throughout most body tissue. The plasma half life is 1.25 to 3 hours, but may be increased by liver damage and following overdosage. Elimination of Acetaminophen is principally by liver metabolism (conjugation) and subsequent renal excretion of metabolites. Approximately 85% of an oral dose appears in the urine within 24 hours of administration, most as the glucuronide conjugate, with small amounts of other conjugates and unchanged drug. (See Overdosage for toxicity information)

Phenyltoloxamine Citrate:
Phenyltoloxamine Citrate is an H1 blocking agent which interferes with the action of histamine primarily in capillaries surrounding mucous tissues and sensory nerves of the nasal and adjacent areas. It has the ability to interfere with certain areas of acetylcholine inhibiting secretions in the nose, mouth and pharynx. It commonly causes CNS depression.

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