Isoprenaline sulphate

Observations of relief of bronchoconstriction without cardiovascular side effects suggest that prostaglandins have a potential clinical role in conditions such as asthma. Cuthbert [273] compared the effect of aerosol-administered PGEi on airways resistance in healthy and asthmatic volunteers with reversible airways obstruction. In the healthy subjects, the forced expiratory volume in one second (FEVi) was unaffected by the prostaglandin when administered as the free acid or as the triethanolamine salt. However, in the asthmatics, inhalation of 55 pg of the triethanolamine salt produced an increase in FEVi comparable in both degree and duration with that produced by an inhalation of 550 jig of isoprenaline sulphate. The triethanolamine salt was employed in the asthmatic trials since it was better tolerated, the free acid being irritant to the upper respiratory tract. Similar results were obtained with PGE2 [274]. 

FIG. 2. Structures of the investigated organic sulphate salts (X) chinine sulphate, (XI) strychnine sulphate, (XII) atropine sulphate, (XIII) bamethane sulphate, (XIV) isoprenaline sulphate, (XV) orciprenaline sulphate, (XVI) amphetamine sulphate. (Ref. 23)). 

Table 4. Doubly and triply charged ions in the FD spectrum of isoprenaline sulphate (XIV). The relative intensities are given in four degrees as in Table 2. (Ref. 23). 

Isoprenaline sulphate is a synthetic drug similar in action to adrenaline it is administered both by inhalation as sprays and orally as tablets. Its quantitative determination by colorimetric methods follows that for adrenaline, although some preparations do not react normally with the iron-citrate reagent. 

Spray of Isoprenaline Sulphate, B,P.C. Contains TO per cent of isoprenaline sulphate with propylene glycol and sodium metabisulphite in water. 

Dilute 5 ml of spray to 50 ml. To 3 ml of the dilution in a 100-ml flask add 2 ml of solution of standard pH 5 4 and make up to volume with water. To 10 ml of this solution add 8 ml of 0 02N iodine and allow to stand for ten minutes. Add 2 ml of 0 1 N sodium thiosulphate and mix. Compare the intensity of colour developed with that produced when 5 ml of a standard solution of isoprenaline sulphate containing TOO g per 100 ml is similarly treated. 

Tablets of Isoprenaline Sulphate, B,P, Usually contain 10 mg of isoprenaline sulphate in a lactose base. The determination follows that given above for sprays.

Dissolve an amount of powdered tablets to contain about 50 mg of isoprenaline sulphate in 100 ml of water containing 3 5 ml of 0 5N hydrochloric acid, filter and dilute to 200 ml. To 10 ml add 2 ml of pH 5 4 buffer and dilute to 100 ml. Continue the determination by the method given under Spray of Isoprenaline Sulphate and calculate the weight in each tablet of average weight. 

A simple spectrophotometric assay follows that for Spray of Isoprenaline Sulphate after dissolving an amount of powdered tablets, equivalent to 100 mg of isoprenaline sulphate, in 200 ml of water and diluting 10 ml of this solution to 100 ml with water. 

Fig. 4.4.12. Separation of a mixture of acidic and basic catecholamines on a LiChrosorb RP-8 column (0.28x25 cm). Eluent Water containing 0.02 M citrate (pH 2.5)/l% propanol/NaCIQ4 (0.08 M)/0.3% sodium dodecyl sulphate. Peaks DHMA, 3,4-dihydroxymandelic acid VMA, vanilmandelic acid HGA, 2,5-dihydroxyphenylacetic acid DOPAC, 3,4-dihydroxyphenylacetic acid 5-HIAA, 5-hydroxyindole-3-acetic acid HVA, homovanillylmandelic acid E, epinephrine NE, norepinephrine N-Syn, norsyneph-rine Syn, synephrine Dopa, 3,4-dihydroxyphenylalanine NM, normetanephrine MN, metanephrine Isopren, isoprenaline 3-H-Tyrm, dopamine Tyrm, tyramine 3-M-Tyrm, 3-methoxytyramine. Reprinted from Ref. 21 with permission.

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