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The pH Analysis of Papaverine-Phentolamine and Prostaglandin E1 for Pharmacologic Erection
0022-534 7/89/1416-1458$02.00/0 Vol. 141, June Printed in U.S.A.
THE JOURNAL OF UROLOGY
Copyright© 1989 by Williams & Wilkins
THE pH ANALYSIS OF PAPAVERINE-PHENTOLAMINE AND PROSTAGLANDIN E 1 FOR PHARMACOLOGIC ERECTION E. JAMES SEIDMON* AND A. MICHAEL SAMAHA, JR. From the Department of Urology, Temple University School of Medicine, Philadelphia Pennsylvania
ABSTRACT
Although papaverine-phentolamine preparations are being employed for pharmacologic erection programs across the nation, their chemical properties have not been described in the literature. We found that the pH of papaverine-phentolamine solution in all concentrations tested remained <4.0. Attempts to buffer the solution resulted in a precipitate at a pH greater than or equal to 5.0. The pH of prostaglandin E 1 was <5.0 but could be easily buffered to pH 7.4 or even 10. 75 and remained stable. The effect of an acidic solution on corporal connective tissue and smooth muscle meshwork is unknown. We believe that buffering by blood will lead to the precipitation of papaverinephentolamine and may cause primary intracorporal scarring. Extravasation or improper injection into the subcutaneous tissue exposes the mixture to blood and may secondarily result in additional scarring for the same reason. Therefore, prostaglandin E 1 may be a more appropriate agent for penile injection. (J. Ural., 141: 1458-1459, 1989) When Michal noted an erection following accidental injection of papaverine into the penile vasculature, a new era began in the diagnosis and treatment of impotence. 1 Virag was the first to report an erection with intracavernosal papaverine injection. 2 • 3 Since that time, many major major medical centers have developed their own pharmacologic erection programs 4 and some centers have hundreds of patients enrolled in selfinjection programs. 5 These institutions are using a papaverinephentolamine preparation with 30 mg.fcc papaverine and one mg.fee phentolamine. 5 The chemical properties of the papaverine-phentolamine mixture have rarely been mentioned in the literature. Does the pH and stability of these compounds have any long term effects on the smooth muscle and connective tissue meshwork of the corpora? Papaverine is an extremely acidic solution. It is supplied in a pH buffered solution at approximately 3.0 and is unstable at high pH. Recently one of the prostaglandins, prostaglandin E 1 (PGE 1, prostin VR pediatric, alprostadil), which is commonly used to maintain the patency of the ductus arteriosus, has been successfully employed for pharmacologic erection. 6 ' 7 The purpose of this study was to test the pH and stability of papaverine alone, in normal saline, in sterile water and with varying concentrations of phentolamine. It was also the intention of this study to perform the same pH testing on PG E 1 and then evaluate the buffering capacities of papaverine-phentolamine and PGE 1 solutions. MATERIALS AND METHODS
pH measurement. Papaverine hydrochloride (10 ml. vials) supplied as 30 mg.fee and phentolamine mesylate (five mg. vials) were used. Ten milligrams ofphentolamine mesylate was reconstituted in one cc of papaverine (30 mg.fee). Varying volumes of papaverine and phentolamine solutions were used to make a total five cc volume which contained different concentrations of phentolamine (table 1). For example, 4.95 cc of papaverine plus 50 µl. of phentolamine gave a total phentolamine concentration of 0.1 mg.fee, whereas 4.00 cc papaverine and one cc of phentolamine gave a phentolamine concentration of 2.0 mg.fee. pH measurements of solutions containing only phentolamine reconstituted in either normal saline or sterile water were also done. Accepted for publication December 15, 1988. *Requests for reprints: Dept. of Urology, Temple University Hospital, Broad and Ontario St., Philadelphia PA 19140.
Using an Orion Research digital analyzer, standardized to a pH of 7.40 with potassium phosphate monobasic NaOH buffer, the pH of each solution was recorded in 10 cc test tubes (table 2). The ion analyzer was restandardized between each reading. The pH of papaverine alone was measured as well as pH of normal saline and sterile water with papaverine added. Buffering of papaverine-phentolamine solution. One microliter aliquot of either 0.1 N NaOH in normal saline or potassium phosphate monobasic NaOH buffer was added to a papaverinephentolamine solution (15 mg. papaverinefcc plus 0.5 mg. phentolaminefcc). The solution was continuously mixed with a magnetic stirring device and the pH was appropriately recorded (table 3). pH of PGE,. Prostaglandin E,, supplied in 0.5 mg./ml. ampules, was used to prepare the solutions. After removing six cc from a 30 cc bottle of normal saline, one ampule of PGE 1 was added. This made a 25 cc volume containing 20 µg.f ml. of PGE1. Five solutions prepared from different PGE 1 ampules were prepared in exactly the same technique. Five cc's from each bottle was placed in a 10 cc test tube. The pH of each solution was recorded from the Orion digital ion analyzer previously standardized to pH of 7.40 and restandardized between readings. Buffering of PGE, solution. Ten, five and one microliter of 0.1 N NaOH were added to solutions #1, #2 and #3 respectively and the pH recorded. To solutions #4 and #5 potassium phosphate buffer with a pH 7.40 was added. The pH values were then recorded for all solutions and any changes in the characteristics of the solutions were noted as well.
RESULTS
The pH of papaverine alone was 3.08 and 3.13. The addition of 0.1 to 1.0 mg.fcc of phentolamine raised the pH from 3.18 to 3.43 respectively. Adding 1.5 and 2.0 mg.fee phentolamine raised the pH to 3.5 and 3.53 respectively. Adding 1.5 and 2.0 mg.Jee phentolamine raised the pH to 3.5 and 3.53 respectively. The pH of normal saline alone was 5.69 and 5. 72 and decreased to 4.35 and 4.13 with the addition of one cc of papaverine to four cc normal saline (table 2). The solution of 15 mg. papaverine and 0.5 mg. phentolaminefcc had a pH of 3.35 to 3.90 whether the phentolamine was reconstituted in normal saline or sterile water (table 3). When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer was added, a fine white
1458
1459 TABLE
Sample
1. Papaverine-phentolamine concentrations
Papaverine 1 (cc)
Phentolamine 2 (µl.)
Total (cc)
Final [Phent] (mg./cc)
5.0 4.95 4.90 4.85 4.80 4.75 4.70 4.65 4.60 4.55 4.50 4.25 4.00 1.00 0.00
0 50 100 150 200 250 300 350 400 450 500 750 1000 0 (4cc NSS)' (5 cc NSS)
5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.50 2.00 0.00 0.00
2 3 4 5 6
7 8
9 10 11 12 13 14 15
'Stock solution: papaverine 30 mg./cc. Stock solution: reconstitution of 10 mg. of phentolamine with 1 cc (30 mg.) of papaverine. 3 NSS = normal saline solution. 2
2. pH measurements of papauerine-phentolamine concentrations
TABLE
Sample #
Exp. #1 pH
Exp.#2 pH
1 2 3 4 5
3.13 3.18 3.34 3.35 3.35 3.34 3.39 3.39 3.40 3.39 3.43 3.50 3.53 4.35 5.72
3.08 3.11 3.14 3.24 3.25 3.27 3.25 3.35 3.39 3.39 3.39 3.40 3.40 4.13 5.69
6
7 8
9 10 11
12 13 14 15
TABLE 3.
pH changes of papauerine-phentolamine when phentolamine is reconstituted in normal saline or sterile water
Phentolamine in H20*
pH
1. 2. 3. 4. 5.
3.43 3.35 3.38 3.40 3.41
Phentolamine in NSS*
pH 3.86 3.85 3.82 3.90 3.88
1. 2. 3. 4.
5.
* 15 mg. papaverine/cc + 0.5 mg. phento!amine/cc. When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer (pH 7.4) was added to the papaverine-phentolamine solution, a fine white precipitate was observed at pH of 5 or greater in all test preparations.
TABLE
4. Buffering effects on prostaglandin E1
Solution
Initial pH*
Buffered pH
1 2 3 4 5
5.09 4.81 4.88 4.86 4.83
10.75 10.30 9.43 7.40 7.40
Observation No No No No No
precip. precip. precip. precip. precip.
* One ampule (500 µg.) in 24 ml. of normal saline = 20 µg./ml. When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer (pH 7.4) was added to the PGE, solution, a NO precipitate was observed at pH of 5 or greater in all test preparations.
precipitate was observed at of five or greater in all preparations tested. The pH of PGE 1 revealed a range of 4.83 to 5.09 in the five preparations tested with the same concentration of 20 µ.g./cc (table 4). With the addition of 10, five and one µ.l. of 0.1 N NaOH the pH values recorded were 10.75, 10.30 and 9.43 respectively. No precipitate or discoloration of the solutions was noted. In sample #4 and #5 both solutions were buffered to pH 7.4 with potassium phosphate monobasic NaOH buffer and again no precipitate or discoloration was noted (table 4). DISCUSSION
Looking at the pH of papaverine alone, with normal saline, sterile water and varying concentrations of phentolamine, our results confirm the acidic pH ofpapaverine. In accordance with the package insert NaOH has been added to the solution to bring the pH to 3.0. Even when phentolamine is added, which is acidic to litmus paper, the pH remains under 4.0. Our results revealed how unstable papaverine is at a higher pH. At a pH >5.0 a precipitate formed from both the papaverine as well as the papaverine-phentolamine solution suggesting that not only does papaverine precipitate out of solution at higher pH but also that phentolamine does not add any stabilization to the solution. When looking at the pH of PGE 1 in five preparations with normal saline, it did not differ from the pH of papaverine in normal saline. However, the most significant difference is that PGE 1 remains stable up to a pH of 10.75 and can easily be buffered to a more physiologic pH of 7.4 using a commercially available phosphate buffer. The papaverine-phentolamine preparation has a pH of 3.0 and papaverine precipitates out of solution at a pH of 5.0. The buffering ability of the corpora has not been studied too date but most probably there is no difference from that of the intravascular compartment. Monkeys, whose corpora was injected with papaverine, showed a histologic change demonstrating significant fibrosis whereas in those monkeys given PGE 1 , no fibrosis was noted. 8 We suggest that this fibrosis may be caused by the precipitation of papaverine and is possibly due to tissue buffering of the injected solution. The pH of PGE 1 preparation is also acidic in normal saline but can be buffered to a more physiologic pH without precipitation. If clinical trials are comparable to papaverine, then PGE 1 would appear to be a better alternative for intracavernous injection than the present solution of papaverine-phentolamine, based on its chemical properties alone. REFERENCES
1. Michal, V., Kramar, R., Pospichal, J. and Hejhal, L.: Arterial cavernous anastomosis for the treatment of sexual impotence. World J. Surg., l: 515, 1977. 2. Virag, R., Frydman, D., Legman, M. and Virag, H.: Intracavernous injection of papaverine as a diagnostic and therapeutic method in erectile failure. Angiology, 35: 79, 1984. 3. Virag, R.: Intracavemous injection of papaverine for erectile failure. Letter to the Editor. Lancet, 2: 938, 1982. 4. Zorgniotti, A. W. and Lefleur, R. S.: Auto-injection of the corpus cavernosum with a vasoactive drug combination for vasculogenic impotence. J. Urol., 133: 39, 1985. 5. Lue, T. F. and Tanagho, E. A.: Physilogy of erecton and pharmacologic management of impotence. J. Urol., 137: 829, 1987. 6. Benson, G.: Intracavernous injection therapy for impotence. J. Urol., 138: 1262, 1987. 7. Virag, R. and Adaikan, P. G.: Effects ofprostaglandin E 1 on penile erection and erectile failure. (letter) J. Urol., 137: 1010, 1987. 8. Aboseif, S. R., Breza, J., Diederichs W., Bosch, R., Benard, F., Stief, C. G., Lue, T. F. and Tanagho, E. A.: Effect of chronic intracavernous injection of papaverine and prostaglandin E 1 on erectile tissue in monkeys. (Abstract #377) J. Urol., 139: 257A, 1988.
THE JOURNAL OF UROLOGY
Copyright© 1989 by Williams & Wilkins
THE pH ANALYSIS OF PAPAVERINE-PHENTOLAMINE AND PROSTAGLANDIN E 1 FOR PHARMACOLOGIC ERECTION E. JAMES SEIDMON* AND A. MICHAEL SAMAHA, JR. From the Department of Urology, Temple University School of Medicine, Philadelphia Pennsylvania
ABSTRACT
Although papaverine-phentolamine preparations are being employed for pharmacologic erection programs across the nation, their chemical properties have not been described in the literature. We found that the pH of papaverine-phentolamine solution in all concentrations tested remained <4.0. Attempts to buffer the solution resulted in a precipitate at a pH greater than or equal to 5.0. The pH of prostaglandin E 1 was <5.0 but could be easily buffered to pH 7.4 or even 10. 75 and remained stable. The effect of an acidic solution on corporal connective tissue and smooth muscle meshwork is unknown. We believe that buffering by blood will lead to the precipitation of papaverinephentolamine and may cause primary intracorporal scarring. Extravasation or improper injection into the subcutaneous tissue exposes the mixture to blood and may secondarily result in additional scarring for the same reason. Therefore, prostaglandin E 1 may be a more appropriate agent for penile injection. (J. Ural., 141: 1458-1459, 1989) When Michal noted an erection following accidental injection of papaverine into the penile vasculature, a new era began in the diagnosis and treatment of impotence. 1 Virag was the first to report an erection with intracavernosal papaverine injection. 2 • 3 Since that time, many major major medical centers have developed their own pharmacologic erection programs 4 and some centers have hundreds of patients enrolled in selfinjection programs. 5 These institutions are using a papaverinephentolamine preparation with 30 mg.fcc papaverine and one mg.fee phentolamine. 5 The chemical properties of the papaverine-phentolamine mixture have rarely been mentioned in the literature. Does the pH and stability of these compounds have any long term effects on the smooth muscle and connective tissue meshwork of the corpora? Papaverine is an extremely acidic solution. It is supplied in a pH buffered solution at approximately 3.0 and is unstable at high pH. Recently one of the prostaglandins, prostaglandin E 1 (PGE 1, prostin VR pediatric, alprostadil), which is commonly used to maintain the patency of the ductus arteriosus, has been successfully employed for pharmacologic erection. 6 ' 7 The purpose of this study was to test the pH and stability of papaverine alone, in normal saline, in sterile water and with varying concentrations of phentolamine. It was also the intention of this study to perform the same pH testing on PG E 1 and then evaluate the buffering capacities of papaverine-phentolamine and PGE 1 solutions. MATERIALS AND METHODS
pH measurement. Papaverine hydrochloride (10 ml. vials) supplied as 30 mg.fee and phentolamine mesylate (five mg. vials) were used. Ten milligrams ofphentolamine mesylate was reconstituted in one cc of papaverine (30 mg.fee). Varying volumes of papaverine and phentolamine solutions were used to make a total five cc volume which contained different concentrations of phentolamine (table 1). For example, 4.95 cc of papaverine plus 50 µl. of phentolamine gave a total phentolamine concentration of 0.1 mg.fee, whereas 4.00 cc papaverine and one cc of phentolamine gave a phentolamine concentration of 2.0 mg.fee. pH measurements of solutions containing only phentolamine reconstituted in either normal saline or sterile water were also done. Accepted for publication December 15, 1988. *Requests for reprints: Dept. of Urology, Temple University Hospital, Broad and Ontario St., Philadelphia PA 19140.
Using an Orion Research digital analyzer, standardized to a pH of 7.40 with potassium phosphate monobasic NaOH buffer, the pH of each solution was recorded in 10 cc test tubes (table 2). The ion analyzer was restandardized between each reading. The pH of papaverine alone was measured as well as pH of normal saline and sterile water with papaverine added. Buffering of papaverine-phentolamine solution. One microliter aliquot of either 0.1 N NaOH in normal saline or potassium phosphate monobasic NaOH buffer was added to a papaverinephentolamine solution (15 mg. papaverinefcc plus 0.5 mg. phentolaminefcc). The solution was continuously mixed with a magnetic stirring device and the pH was appropriately recorded (table 3). pH of PGE,. Prostaglandin E,, supplied in 0.5 mg./ml. ampules, was used to prepare the solutions. After removing six cc from a 30 cc bottle of normal saline, one ampule of PGE 1 was added. This made a 25 cc volume containing 20 µg.f ml. of PGE1. Five solutions prepared from different PGE 1 ampules were prepared in exactly the same technique. Five cc's from each bottle was placed in a 10 cc test tube. The pH of each solution was recorded from the Orion digital ion analyzer previously standardized to pH of 7.40 and restandardized between readings. Buffering of PGE, solution. Ten, five and one microliter of 0.1 N NaOH were added to solutions #1, #2 and #3 respectively and the pH recorded. To solutions #4 and #5 potassium phosphate buffer with a pH 7.40 was added. The pH values were then recorded for all solutions and any changes in the characteristics of the solutions were noted as well.
RESULTS
The pH of papaverine alone was 3.08 and 3.13. The addition of 0.1 to 1.0 mg.fcc of phentolamine raised the pH from 3.18 to 3.43 respectively. Adding 1.5 and 2.0 mg.fee phentolamine raised the pH to 3.5 and 3.53 respectively. Adding 1.5 and 2.0 mg.Jee phentolamine raised the pH to 3.5 and 3.53 respectively. The pH of normal saline alone was 5.69 and 5. 72 and decreased to 4.35 and 4.13 with the addition of one cc of papaverine to four cc normal saline (table 2). The solution of 15 mg. papaverine and 0.5 mg. phentolaminefcc had a pH of 3.35 to 3.90 whether the phentolamine was reconstituted in normal saline or sterile water (table 3). When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer was added, a fine white
1458
1459 TABLE
Sample
1. Papaverine-phentolamine concentrations
Papaverine 1 (cc)
Phentolamine 2 (µl.)
Total (cc)
Final [Phent] (mg./cc)
5.0 4.95 4.90 4.85 4.80 4.75 4.70 4.65 4.60 4.55 4.50 4.25 4.00 1.00 0.00
0 50 100 150 200 250 300 350 400 450 500 750 1000 0 (4cc NSS)' (5 cc NSS)
5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.50 2.00 0.00 0.00
2 3 4 5 6
7 8
9 10 11 12 13 14 15
'Stock solution: papaverine 30 mg./cc. Stock solution: reconstitution of 10 mg. of phentolamine with 1 cc (30 mg.) of papaverine. 3 NSS = normal saline solution. 2
2. pH measurements of papauerine-phentolamine concentrations
TABLE
Sample #
Exp. #1 pH
Exp.#2 pH
1 2 3 4 5
3.13 3.18 3.34 3.35 3.35 3.34 3.39 3.39 3.40 3.39 3.43 3.50 3.53 4.35 5.72
3.08 3.11 3.14 3.24 3.25 3.27 3.25 3.35 3.39 3.39 3.39 3.40 3.40 4.13 5.69
6
7 8
9 10 11
12 13 14 15
TABLE 3.
pH changes of papauerine-phentolamine when phentolamine is reconstituted in normal saline or sterile water
Phentolamine in H20*
pH
1. 2. 3. 4. 5.
3.43 3.35 3.38 3.40 3.41
Phentolamine in NSS*
pH 3.86 3.85 3.82 3.90 3.88
1. 2. 3. 4.
5.
* 15 mg. papaverine/cc + 0.5 mg. phento!amine/cc. When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer (pH 7.4) was added to the papaverine-phentolamine solution, a fine white precipitate was observed at pH of 5 or greater in all test preparations.
TABLE
4. Buffering effects on prostaglandin E1
Solution
Initial pH*
Buffered pH
1 2 3 4 5
5.09 4.81 4.88 4.86 4.83
10.75 10.30 9.43 7.40 7.40
Observation No No No No No
precip. precip. precip. precip. precip.
* One ampule (500 µg.) in 24 ml. of normal saline = 20 µg./ml. When either 0.1 N NaOH or potassium phosphate monobasic NaOH buffer (pH 7.4) was added to the PGE, solution, a NO precipitate was observed at pH of 5 or greater in all test preparations.
precipitate was observed at of five or greater in all preparations tested. The pH of PGE 1 revealed a range of 4.83 to 5.09 in the five preparations tested with the same concentration of 20 µ.g./cc (table 4). With the addition of 10, five and one µ.l. of 0.1 N NaOH the pH values recorded were 10.75, 10.30 and 9.43 respectively. No precipitate or discoloration of the solutions was noted. In sample #4 and #5 both solutions were buffered to pH 7.4 with potassium phosphate monobasic NaOH buffer and again no precipitate or discoloration was noted (table 4). DISCUSSION
Looking at the pH of papaverine alone, with normal saline, sterile water and varying concentrations of phentolamine, our results confirm the acidic pH ofpapaverine. In accordance with the package insert NaOH has been added to the solution to bring the pH to 3.0. Even when phentolamine is added, which is acidic to litmus paper, the pH remains under 4.0. Our results revealed how unstable papaverine is at a higher pH. At a pH >5.0 a precipitate formed from both the papaverine as well as the papaverine-phentolamine solution suggesting that not only does papaverine precipitate out of solution at higher pH but also that phentolamine does not add any stabilization to the solution. When looking at the pH of PGE 1 in five preparations with normal saline, it did not differ from the pH of papaverine in normal saline. However, the most significant difference is that PGE 1 remains stable up to a pH of 10.75 and can easily be buffered to a more physiologic pH of 7.4 using a commercially available phosphate buffer. The papaverine-phentolamine preparation has a pH of 3.0 and papaverine precipitates out of solution at a pH of 5.0. The buffering ability of the corpora has not been studied too date but most probably there is no difference from that of the intravascular compartment. Monkeys, whose corpora was injected with papaverine, showed a histologic change demonstrating significant fibrosis whereas in those monkeys given PGE 1 , no fibrosis was noted. 8 We suggest that this fibrosis may be caused by the precipitation of papaverine and is possibly due to tissue buffering of the injected solution. The pH of PGE 1 preparation is also acidic in normal saline but can be buffered to a more physiologic pH without precipitation. If clinical trials are comparable to papaverine, then PGE 1 would appear to be a better alternative for intracavernous injection than the present solution of papaverine-phentolamine, based on its chemical properties alone. REFERENCES
1. Michal, V., Kramar, R., Pospichal, J. and Hejhal, L.: Arterial cavernous anastomosis for the treatment of sexual impotence. World J. Surg., l: 515, 1977. 2. Virag, R., Frydman, D., Legman, M. and Virag, H.: Intracavernous injection of papaverine as a diagnostic and therapeutic method in erectile failure. Angiology, 35: 79, 1984. 3. Virag, R.: Intracavemous injection of papaverine for erectile failure. Letter to the Editor. Lancet, 2: 938, 1982. 4. Zorgniotti, A. W. and Lefleur, R. S.: Auto-injection of the corpus cavernosum with a vasoactive drug combination for vasculogenic impotence. J. Urol., 133: 39, 1985. 5. Lue, T. F. and Tanagho, E. A.: Physilogy of erecton and pharmacologic management of impotence. J. Urol., 137: 829, 1987. 6. Benson, G.: Intracavernous injection therapy for impotence. J. Urol., 138: 1262, 1987. 7. Virag, R. and Adaikan, P. G.: Effects ofprostaglandin E 1 on penile erection and erectile failure. (letter) J. Urol., 137: 1010, 1987. 8. Aboseif, S. R., Breza, J., Diederichs W., Bosch, R., Benard, F., Stief, C. G., Lue, T. F. and Tanagho, E. A.: Effect of chronic intracavernous injection of papaverine and prostaglandin E 1 on erectile tissue in monkeys. (Abstract #377) J. Urol., 139: 257A, 1988.