CAVERJECT ® zErectile dysfunction? zHighly unstable zStore below -5ºC zExpire in 2mths from date of manufacture zUse within 48hrs after removal from freezer zProstaglandin E 1 (alprostadil)

Name: Kiat Nee Kho; Supervisor: John Parkin USE OF DEUTERIUM OXIDE TO STABILISE PROSTAGLANDIN E 1 AGAINST CHEMICAL DEGRADATION

Why deuterium oxide? zheavier mass than hydrogen zsignificant isotopic effects zreduce reaction rate zextent shelf-life

Use of D 2 O to stabilise a compounds: zindocyanine green ztauromustine zbenactyzine zproteins and polypeptides - tubulin, ovabumin, protein G zoral polio vaccine

How safe is deuterium oxide? zno radiation risk znatural isotopic abundance (1-6400) zhuman body - 75mg/kg body weight ztoxic effects - >20% of total fluid is replaced by deuterium oxide zsafe - esp. in IV products as D 2 O is mixed &distributed quickly with body fluid

Why Prostaglandin E 1 ? zexpensive zhighly unstable zsmall volume parenteral product zadministered by intravenous infusion zProstin VR ® - supplied by Pharmacia & Upjohn

Objectives zTo investigate the effect of D 2 O on the degradation rate of PGE 1 zTo study the pH and temperature effects on the degradation of PGE 1 in water and D 2 O zTo evaluate the shelf-life of PGE 1 in water and D 2 O

Experimental Test solutions: z20  L PGE 1 solution in 1mL deuterated buffer (reconstituted with D 2 O) Control solutions: z20  L PGE 1 solution in 1mL aqueous buffer (reconstituted with H 2 O) Studies of pH effect :pH (temp. 60ºC) Studies of temp. effect : temp ºC (pH 7.4)

Deuterated buffers zprepare aqueous buffers zevaporate at 105ºC -- dry phase buffers zadd 2 drops of D 2 O zre-evaporate at 105ºC zanhydrous deuterated buffers zstore in a desiccator zreconstitute with D 2 O when needed

Results - Effect of pH

zRate constants, k, are higher in H 2 O --> faster degradation zAverage of fold increase in stability over pH 2-8 zPGE 1 is more stable in D 2 O then in H 2 O under all conditions

Results - Effect of temperature

zover 44-68ºC, D 2 O stabilise PGE 1 by fold zrate constants, k, are lower for PGE 1 in D 2 O than those in H 2 O

Results - Shelf-lives of PGE 1

Discussions zLog concentration vs time plot - straight line --> 1st order reaction zHigher the temperature, faster the degradation --> temperature dependent reaction

Degradation route of Prostaglandin E 1

Discussions zTest and control solutions were under same conditions except different nature of vehicle zThus, the stability effect was due to deuterium oxide

Discussions How D 2 O stabilise PGE 1 ? zHeavier mass zIsotopic effects zStronger deuterium bonds (compare to hydrogen bonds) zLess ionisation extent

Discussions zDeuterium exchange quickly with hydrogen zDecelerates the reactions involving hydrogen zPossibility and extent of the exchange is unknown zIncrease in stability is due to involvement of D 2 O

Conclusion zD 2 O stabilise PGE 1 by at least 1.5 fold over pH 2-8 at temperature 44-68ºC zThe shelf life of PGE 1 is extended with incorporation of D 2 O zExchange of hydrogen with deuterium occurred in substituting H 2 O with D 2 O --> lead to decrease of degradation rate

Conclusion Future directions: zstabilisation effect of D 2 Oand other agents (eg. cyclodextrin) on PGE 1 zstabilisation effect of D 2 O on recombinant proteins or polynucleotides zclinical trial on safety of D 2 O

THE END