[Influence of Perftoran nanoemulsion on blood plasma concentrations of lipophilic drugs]

The influence of perfluorocarbon blood substitute Perfloran on the plasma concentrations of bendazole, drotaverine, ketorolac and verapamil upon intravenous introduction after Perfloran infusion (5 ml/kg) has been investigated on rabbits. It has been found that the plasma concentrations of verapamil, drotaverine and bendazole (highly lipophilic drugs with log(P) = 4.5, 4.9 and 3.5, respectively) increased in the presence of Perfloran. The influence of Perfloran on the concentration of weakly lipophilic ketorolac was less significant. Perfloran effectively bound drotaverine, ketorolac and verapamil in vitro, whereas the binding of ketorolac by the emulsion particles was weak. Evidently, the infusion of hydrophobic nanoemulsion Perftoran elevates the sorption capacity of plasma and creates prerequisites for the redistribution drugs and favors increase in their concentrations.

[Analysis of 37 drugs in whole blood by HPLC after solid phase extraction]

OBJECTIVE

To develop a specific, sensitive, reproducible SPE-HPLC method for the determination of 37 drugs in whole blood.

METHODS

With the doxapram as internal standard, Oasis column was used to extract drugs from whole blood. Two kinds of mobile phases were used in this study. Separations were achieved by a LiChrospher 100 RP-C18 (250 mm x 4.0 mm x 5 microm) column kept at 50 degrees C, the DAD detector was set at 230 nm and 250 nm.

RESULTS

The limit of detection were 1-30 ng/mL. The method showed excellent linearity and the linear correlation coefficient was > or =0.997 98. The relative standard deviation for between-day and within-day assay were <10%.

CONCLUSION

The method is effective, simple, reliable and has been used in real cases.

The Significance of Putative Urinary Markers of Illicit Heroin Use After Consumption of Poppy Seed Products

After consumption of poppy seeds various substances were detected in urine or blood samples using an immunoassay and a sophisticated liquid chromatographic-tandem mass spectrometric procedure. These compounds are widely considered to be putative markers of heroin (HER) abuse whereas acetylcodeine was regarded as a marker for illicit preparations ("street HER"). Besides positive urinary opiate immunoassay results during a 48 hours monitoring period, peak concentrations of morphine (MOR), codeine and their glucuronides appeared 4 to 8 hours after ingestion of poppy seeds, and concentrations of total MOR higher than 10 microg/mL were observed. Also, in serum samples taken up to 6 hours after consumption, MOR glucuronides were found. Free MOR was only detected in traces (1 to 3 ng/mL) within 2 hours of consumption. In addition, 3 of 6 onsite opiate sweat tests revealed positive results 6.5 hours after ingestion. Furthermore, it was demonstrated that neither noscapine (NOS) nor papaverine (PAP) was detectable in urine or blood samples after the consumption of poppy seeds containing up to 94 microg NOS and up to 3.3 mug PAP. NOS and PAP were rapidly metabolized, whereas desmethylpapaverine and, especially, its glucuronide were found in urine samples of poppy seed consumers even 48 hours after consumption. According to these results PAP metabolites should not be regarded as markers of illicit HER abuse. In conclusion, only acetylcodeine can be regarded as a specific marker but has the problem of a short half-life. Therefore, we suggest that NOS and PAP, but not their metabolites, might be used cautiously as additional markers of illicit HER abuse as they have not been detected after oral intake of poppy seeds in normal doses. But it must be kept in mind that in some cases poppy seeds with an unusually high content of these alkaloids could be available, and that these substances are also agents in some pharmaceuticals.

Application of new membrane selective electrodes for the determination of drotaverine hydrochloride in tablets and plasma

The construction and electrochemical response characteristics of poly vinyl chloride (PVC) membrane sensors for the determination of drotaverine hydrochloride were described. The sensors are based on the use of the ion association complexes of drotaverine cation with sodium phosphotungestate (Dro-PTA) or ammonium reineckate (Dro-R) counter anions as ion exchange sites in the PVC matrix. The performance characteristics of these sensors, which were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response for drotaverine over the concentration range 10(-5) to 10(-2) M with cationic slopes of 49.55 and 51.36 mV per concentration decade. The direct potentiometric determination of drotaverine hydrochloride using the proposed sensors gave average recoveries of 99.95+/-0.71 and 100.04+/-0.60 for Dro-PTA and Dro-R, respectively. The sensors are used for determination of drotaverine hydrochloride in tablets, in its mixture with caffeine and paracetamol and in plasma. Validation of the method shows suitability of the proposed sensors for use in the quality control assessment of drotaverine hydrochloride. The developed method was found to be simple, accurate and precise when compared with a reported HPLC method.

Tissue distribution of moxaverine-hydrochloride in the rabbit eye and plasma

OBJECTIVE

The aim of this study was to determine the tissue distribution and epithelial penetration of moxaverine-hydrochloride (MOX) in the rabbit eye.

METHODS

For systemic application, a radioactively labeled MOX solution was injected into the ear vein of Dutch-belted pigmented male rabbits. For topical dosing, an identical solution was administered. At predetermined time points, rabbits were sacrificed, the eyes dissected, and the amount of MOX in the ocular tissues measured. To examine the MOX permeability across the corneal epithelium, transport studies using rabbit corneal epithelial cell culture were conducted and the respective apparent permeability coefficient in absorptive (a to b) or secretive (b to a) direction was calculated.

RESULTS

Topical delivery resulted in high concentrations of MOX in the cornea and conjunctiva, although other tissues of the anterior part yielded lower MOX concentrations. In the tissues of the posterior part, high amounts were detected in the retina. Plasma levels were low. The apparent permeability coefficient across corneal epithelial cell layers was in the range of 10(5) cm/s, exhibiting no apparent directionality.

CONCLUSION

A topical dosing of MOX to posterior regions of the eye seems feasible. MOX levels in the posterior part of the eye were remarkably high, without causing stringent plasma levels. The high apparent permeability coefficient of MOX across the corneal epithelial cell layers might be caused by the lipophilic nature of the drug and was in the range of other compounds with comparable physicochemical properties.

[Determination of papaverine hydrochloride in skin and blood and the drug contents in pig skin]

OBJECTIVE

To explore the application of ultraviolet spectrophotometer in determining papaverine hydrochloride content in blood and skin and to determine the intradermal content after local external application of papaverine hydrochloride.

METHODS

Phosphate buffer solution (pH = 10, ionic strength = 0.4) was added into the blood or ground skin tissue containing papaverine hydrochloride, and papaverine hydrochloride was extracted with chloroform-hexane mixture (ratio:2:3). After oscillation and centrifugation, partial organic phase was retrieved and dried in 60 degrees C water bath. The dried product was dissolved in 1 mol/L HCl and then underwent filtration through 0.2 micron membrane. The ultraviolet apectrophotometry was applied to determine the content of papaverine hydrochloride in the filtrate. 2% papaverine hydrochloride cream was applied on pig's skin and skin specimen was retrieved at given time to determine the papaverine hydrochloride content in skin tissue with ultraviolet spectrophotometry.

RESULTS

The absorbance spectrum of the extract was typical of that of papaverine hydrochloride, with no miscellaneous peak. The extractive rate of papaverine hydrochloride in blood of was more than 92% and that in skin tissue more than 87%. Eight hours after external application of 2% papaverine hydrochloride cream on pig skin, the content of papaverine hydrochloride in skin tissue was more than 90 micrograms/g, significantly higher than the effective concentration of papaverine hydrochloride.

CONCLUSIONS

Ultraviolet spectrophotometry is a simple, economical and reliable method for the determination of papaverine hydrochloride content in blood and skin tissue, with good reproducibility and sensibility. External application of papaverine hydrocholine cream can provide efficient permeation and drug concentration in the skin.

Evaluation of several solid phase extraction liquid chromatography/tandem mass spectrometry on-line configurations for high-throughput analysis of acidic and basic drugs in rat plasma

Several configurations using 6- and 10-port switching valves were studied for high flow, on-line extraction of rat plasma coupled to an electrospray triple quadrupole mass spectrometer. Each plasma sample was diluted 1:1 with an aqueous internal standard solution. The sample was injected into a 2.1 x 20 mm cartridge column packed with 25 microm divinylbenzene/N-vinylpyrrolidone packing using 100% aqueous mobile phase at 4 mL/min. After sample loading and sample cleanup, the analytes were eluted from the extraction column with a 1.0-min gradient at 0.4 mL/min. The samples were either analyzed directly after elution from the extraction column or after additional separation using a short high performance liquid chromatography (HPLC) column. The different configurations were tested using an acidic drug (diflunisal) and a basic drug (clemastine) in rat plasma. On-line analysis was performed by injecting 200 microL of diluted plasma. The mass spectrometer was operated in the multiple reaction monitoring (MRM) mode. All calibration standards gave relative standard deviations (RSDs) below 5%. The total time per sample was 3 min.

Papaverine topical gel for treatment of erectile dysfunction

Intracavernous injection of vasoactive substances has been shown to be an effective means of treatment of organic erectile dysfunction. However, up to 50% of men eventually discontinue treatment often because of lack of spontaneity and needle phobia. This study was done as a phase I, placebo controlled, nonblinded investigation of the safety and efficacy of a topical papaverine gel in the treatment of erectile dysfunction. Of 20 men with organic impotence 17 completed the trial and 13 of these patients had spinal cord injuries. After application of a 15% and 20% papaverine base gel to the scrotum, perineum and penis, cavernous artery diameter was significantly increased (36%, p < 0.001) as assessed by color flow Doppler ultrasound. Peak systolic flow velocity increased 26%. Only 3 of 14 patients achieved an increase in cavernous artery diameter of 75% or more and 2 of 14 had a peak systolic flow velocity of 25 cm. per second or more after application of a topical base gel. Similar findings were present when only the patients with spinal cord injury were analyzed. The effect of a papaverine base in producing flow alterations to the penis is dose-dependent. A diminution in blood pressure was present at 15 and 30 minutes after application to the forearm, and the heart rate diminished from 68 to 62 beats per minute after application to the genitalia. No patient was symptomatic. Serum papaverine levels were not elevated over pre-application values. No hepatotoxic effects were demonstrated. Full clinical erections (mean duration 38.7 minutes) were present in 3 patients but were also present with the placebo preparation (mean duration 8.0 minutes). In conclusion, topical papaverine gel appears to be safe and well tolerated after application to the genitalia, and increases blood flow to the penis with a 15% and 20% base preparation. Minimal systemic absorption occurs and, thus, effects are probably from local absorption. Topical therapy appears to augment reflex erections in the spinal cord injury patient and may be especially beneficial in this population. Further investigation is warranted at higher concentrations or in combination with different skin absorption enhancers.

High-performance liquid chromatographic method for the determination of drotaverine in human plasma and urine

A simple and sensitive HPLC method for the determination of drotaverine in human plasma and urine has been developed. Alkalinized plasma or urine was extracted with organic solvent and the basic components in the organic phase were back-extracted into 0.1 M HCl. An aliquot of the aqueous layer was injected onto the column and the eluent was monitored at 254 nm. Separation was performed on a C18-column with 0.02 M sodium dihydrogen phosphate-methanol (30:70, v/v) containing perchlorate ion at pH 3.2 as mobile phase. Drotaverine was well resolved from the plasma constituents and internal standard. An excellent linearity was observed between peak-height ratios and plasma concentrations and the intra- and inter-assay coefficients of variation were always < 10%. The lowest limit of detection (signal-to-noise ratio 3:1) was 6 ng/ml. The method is suitable for therapeutic monitoring and pharmacokinetic studies of drotaverine in humans as well as in animal models.

Modified high-performance liquid chromatographic method for analysis of drotaverine in human plasma

An HPLC method is described for the determination of drotaverine in plasma; papaverine is used as the internal standard. The lower limit of quantitation is 50 ng ml-1 with an inter-assay precision (RSD) of below 4%. The method has been validated and successfully used to assay clinical trial samples in healthy volunteers.

Pharmacokinetics and bioavailability of papaverine HCl following intravenous, peroral, rectal, vaginal, topical and buccal administration in beagle dogs

This in vivo study was designed to obtain bioavailability data and a definite pharmacokinetic profile of papaverine HCl in Beagle dogs following intravenous (IV), peroral (PO), rectal, vaginal, topical, and buccal administration of different papaverine HCl formulations. Blood samples were analyzed by high-performance liquid chromatography. The pharmacokinetic parameters were determined using either a curve fitting program (RESID) or a compartment model independent program (AUC-RPP). The plasma concentration-time profiles show that papaverine HCl pharmacokinetics is best described by an open two-compartment model. The absolute bioavailability of papaverine HCl was determined to be 57.2 per cent, 25.2 per cent, 53.2 per cent, 3.2 per cent and 7.5 per cent, respectively, following P.O., rectal, vaginal, topical and buccal administration.

[An attempt to classify vascular impotence using penile erection curve patterns]

Papaverine hydrochloride was administered to the cavernous body of the penis in a total of 262 patients who were diagnosed as impotent at our Reproduction Center, Toho University, during the 5 years' period from 1984 to 1988. The condition of erection was accurately recorded by the use of both a mercury strain gauge and rubber strain gauge to classify the erection curve, and papaverine hydrochloride outflow into the peripheral blood was concurrently measured in some of the cases in order to assess its relation with the erection curve pattern. As for the concentration of papaverine hydrochloride in the peripheral blood, it was found that the better the state of erection, the smaller the outflow of peripheral blood. An assessment of the relationship of the concentration of papaverine hydrochloride with the classification of erection pattern showed that the amount of outflow was smaller in the N type (normal) pattern and that the amount of outflow was increasingly larger in the following order: A type (arterial), N' type (arterial and venous) and V type (venous). The distribution of the erection curve patterns, in the 262 cases was: N type, 45%; A type, 10%; N' type, 22.5%; and V type, 22.5%. From the above findings, it is presumed that classification of erection curve pattern under papaverine hydrochloride loading is useful for the differentiation of vascular impotence, particularly for the diagnosis of disorders in the outflow system.

Pharmacokinetics of papaverine HCl upon intravenous route of administration in old and young beagle dogs

This in vivo study was designed to compare the pharmacokinetics of papaverine HCl in young and old Beagle dogs following intravenous (i.v.) administration of papaverine HCl. Blood samples were analyzed by high performance liquid chromatography. The pharmacokinetic parameters were first determined using a curve fitting program (RESID), and then evaluated by SAS statistics. The plasma concentration-time profiles show that papaverine HCl pharmacokinetics is best described by an open two-compartment model. The only age-dependent significant difference in pharmacokinetic behavior between young and old Beagle dogs was found concerning the distribution rate constants.

Papaverine hydrochloride in peripheral blood and the degree of penile erection

Papaverine hydrochloride was injected into the penis in 32 impotent patients, and peripheral blood concentrations were measured at 3, 5, 10, 15 and 30 minutes. The patients then were divided into groups according to the rate of increase of the penile circumference (20% or more complete erection, 10 to 19% and less than 9% groups). Patients with a more complete erection had a significantly lower concentration of papaverine hydrochloride in the peripheral blood at 3 minutes after administration (p less than 0.05). Therefore, patients who do not respond to papaverine have some defect in the venous closure system.

Effect of papaverine on pulmonary vascular permeability to proteins

Previous studies have suggested that papaverine, a drug commonly used in studies of transvascular fluid and solute exchange to eliminate confounding effects of changes in vascular tone, may itself increase vascular permeability. In this study, we determined the ability of papaverine to alter pulmonary vascular protein permeability by measuring the osmotic reflection coefficient (sigma) for total proteins in a canine isolated perfused left lower lung lobe (LLL) preparation. The reflection coefficient, determined by the hematocrit-protein double-indicator technique, for control LLL's was 0.83 +/- 0.04 (SE) (n = 7). In separate groups of LLL's, blood papaverine HCl concentrations of 10(-5), 10(-4), and 10(-3) M resulted in sigma's of 0.84 +/- 0.02 (n = 6), 0.73 +/- 0.04 (n = 7), and 0.53 +/- 0.04 (n = 6), respectively. When two LLL's from the 10(-4) M group with sigma's of 0.56 and 0.57 were excluded from the analysis, the average sigma for this group was 0.79 +/- 0.02. We conclude that papaverine increases protein permeability at a concentration of 10(-3) M but does so in only some lobes at 10(-4) M. These results suggest that caution be taken when using high concentrations of papaverine in fluid balance studies.

A new method for high-performance liquid chromatographic determination of drotaverine in plasma

A sensitive, specific high-performance liquid chromatographic procedure was developed for the determination of plasma drotaverine levels. Basic plasma samples were adjusted to pH 1.5 and extracted with chloroform. HPLC [n-heptane-dichloromethane-diethylamine (50:25:2)] on a microporous silica column, with a variable-wavelength UV detector set at 302 nm allowed the measurement of drotaverine at the 50-ng/mL level. The utility of this method for determination of drotaverine in dog and rat plasma was demonstrated.

The fate of Drotaverine-Acephyllinate in rat and man II. Human pharmacokinetics of Drotaverine-14C-Acephyllinate

Pharmacokinetics of Drotaverine-Acephyllinate, Chinoin was investigated in seven male volunteers using 14C labelled drug. Drotaverine-Acephyllinate was administered at a 100 mg single oral dose. Measurements of total radioactivity showed that the drug was absorbed completely and was eliminated by renal and biliary routes. Within 72 hours 39.9 +/- 9.9% and 47.1 +/- 4.9% of the dose were recovered in the urine and faeces respectively. Experimental results were interpreted on the basis of a complex linear compartment model. The structural identifiability of the model was proved by computer analysis, and the pharmacokinetic parameters were determined.

Comparison of the effects of intravenous papaverine hydrochloride and oral pavabid HP capsulets on regional cerebral blood flow in normal individuals

A single-blind study was conducted in 13 right-handed normal male subjects to compare the effects of oral and i.v. papaverine on regional cerebral blood flow (rCBF). Six xenon-133 inhalation rCBF measurements were performed on each subject; three tests--baseline, placebo, and drug evaluations--were carried out on each of two separate days. The oral and i.v. drugs were randomized for first-day administration. rCBF, measured as flow gray (FG), increased significantly (p less than or equal to 0.001) from baseline with both drug forms. Increases of 10.53% and 13.94% (left and right hemispheres, respectively) were demonstrated 90 min after a single 600-mg dose of oral papaverine. Increases of 5.09% and 8.69%, respectively, were recorded immediately after a single 100-mg dose of i.v. papaverine. FG also increased significantly (p less than or equal to 0.001) for both drug forms when compared to that of placebo. Placebo produced only a slight increase (not significant) with both the oral and i.v. groups. The data show increasing rCBF in normal subjects.

Plasma levels of ethaverine after oral administration to humans

Fourteen healthy human subjects received a 200 mg oral dose of ethaverine hydrochloride as an elixir. Blood samples were obtained for 12 h after dosing. Plasma ethaverine concentrations were determined using a paired-ion, reversed-phase high performance liquid chromatographic method. Individual plasma concentration-time profiles were fitted to a two-compartment model with first-order absorption. The ethaverine was rapidly absorbed, based on a time of maximum plasma concentration of 0.75 h, a time-lag of 8.4 min, and an apparent first-order absorption half-life of 8.6 min. The mean terminal elimination half-life was 3.3 h.

Biopharmaceutical aspects of Depogen

The absorption of Depogen was studied on an in vitro model and in various laboratory animals using stoichiometrically equivalent doses of drotaverin (No-Spa) calculated for drotaverin base for comparison. Blood levels of the drug were assessed by radiochemical and microchemical methods. Based on the results obtained and pharmacokinetic properties, the expectable optimal dosage and formulations for the possible field of indication were elaborated.

Beneficial effect of papaverine plus raubasine in peripheral arterial insufficiency

It has been demonstrated that, in most arteriopathic patients, vasodilators induce the vascular steal phenomenon, i.e. the shunting of blood from the ischemic to the normally perfused areas. It is conceivable, therefore, that vasoconstrictors may improve in the opposite way, reducing the blood flow to the normal zones and increasing it to the ischemic. A "reverse vascular steal" caused by the simultaneous IV injection of a vasodilator and a beta-blocker has been previously shown; however, the chronic treatment of arteriopathic patients with beta-adrenoceptor blocking drugs often results in increased evidence of peripheral arterial insufficiency; therefore, the combination of a vasodilating drug with a beta-blocker is limited in the clinical practice. The aim of this study was to investigate the efficacy of the combination of the vasodilator papaverine hydrochloride with a drug having vasoconstrictive action without the undesirable side effects of beta-blockers. Accordingly, raubasine (40 mg) was given p.o. associated with papaverine (300 mg) in 10 arteriopathic patients, who presented a significant reduction of blood flow in the affected limb after the administration of 300 mg p.o. of papaverine alone. The measurements of blood flow were performed by impedance plethysmographic recordings to evaluate papaverine plasma concentrations. Data obtained by this study indicate that papaverine alone induces a significant reduction of blood flow starting from the time of its maximal plasma concentration. Raubasine alone does not induce any change in blood flow, while the combination of the 2 drugs significantly increases the blood supply to the affected limb. These favorable results, probably related to the ability of raubasine to induce a reverse vascular steal, suggest that the combination of this drug with a vasodilator such as papaverine may represent a new approach in the treatment of peripheral arterial insufficiency.

Papaverine bioavailability in delayed absorption formulations

The bioavailability of non "normal-acting" and three "delayed" papaverine formulations was compared in twenty hospitalized human subjects. Papaverine was evaluated in the blood at the nanogram level by a highly sensitive, specific gas chromatographic method with electron capture detection. Only one of the three chronoid preparations had appropriately delayed bioavailability 89% in comparison to normal acting formulation.

Determination of the antispasmodic agent ethaverine in human plasma by high-performance liquid chromatography

Ethaverine can be measured in the plasma of human subjects by reversed-phase high-performance liquid chromatography employing UV detection. The limit of detection was 2 ng/ml, and the precision was +/- 14, +/- 6 and +/- 2% at concentrations of 5, 25 and 50 ng/ml respectively. A peak mean plasma drug concentration of 20 ng/ml occurred at 1.5 h after single oral doses of a capsule formulation to human subjects, and declined with a half-life of 2.9 h.

Simple and rapid high-pressure liquid chromatographic determination of papaverine in plasma

A rapid and sensitive high-pressure liquid chromatographic (HPLC) assay is described for the quantification of papaverine in plasma. A paired-ion, reversed-phase system was employed with detection at 254 nm. This procedure yielded reproducible results with a sensitivity of 2 ng/ml. Total extraction and quantification time was less than 1 hr. The suitability of this procedure for plasma sample analysis from a bioavailability study was demonstrated.

The influence of dosage form on papaverine bioavailability

The bioavailability of sustained-release papaverine HCl dosage forms were compared to equivalent doses of the drug administered as an elixir and conventional compressed tablets to 12 healthy human subjects. Papaverine plasma levels were determined using a gas-chromatographic procedure. The drug was absorbed more rapidly and completely from the two nonsustained-release formulations. There was a large intersubject variability, and the plasma half-life of the drug was esstimated to be 1 hour. The area under the plasma level-time curve for the nine sustained-release products ranged from 18 to 64% relative to the area achieved by the papaverine elixir. It was concluded that the sustained-release dosage forms of papaverine included in each study group could be considered bioequivalent, but they exhibited inadequate bioavailability relative to either the elixir or the compressed tablet dosage form.

Determination of papaverine in blood samples by gas chromatography using a flame-ionization and a nitrogen-phosphorus detector

The determination of papaverine in blood samples using a flame-ionization and a nitrogen-phosphorus detector is described. The method is quite simple and permits the determination of papaverine at blood levels at 5-500 ng/ml.

Arterial flow in the lower leg correlated with plasma levels of two formulations of papaverine hydrochloride

In patients with severe peripheral vascular disease (mean arterial flow of 40 ml/min), a suspension of papaverine in a soft gelatin capsule produced plasma levels almost three times higher than those following treatment with a sustained-release tablet formulation. The higher plasma levels resulted in significantly greater vasodilation with increased distal arterial flow. The onset of peak pulsatile flow with the soft gelatin form came sooner than with the sustained-release form. However the durations of vasodilation were similar with both papaverine preparations. The vasodilatory activity of papaverine appeared to be greater in the sympathectomized leg. The soft gelatin formulation of papter reconstruction of a large artery, and may be effective in sustaining a longer vasodilatory effect in patients with small vessel disease, when surgical procedures may not be applicable.

A controlled release papaverine tablet (Papacontin): a study in normal volunteers

1. A controlled release tablet containing 300 mg of papaverine hydrochloride was compared with a capsule containing the same dose. 2. The in vitro release pattern showed a steady dissolution of the tablet, with release of the papaverine over 10 h, whereas the capsule release time was 40 min. 3. Plasma levels in volunteers who were given the tablet showed a rapid rise to therapeutic levels (150-300 ng/ml) within 1 h, and maintenance of these levels for 10-12 h, with no accumulation on repeated 12 hourly dosage. Administration of the capsule produced early peaking and a subsequent rapid fall in plasma levels.

Comparison of soft gelatin capsule vs. sustained release formulation of papaverine HCl: vasodilation and plasma levels

The vasodilatory action, plasma papaverine levels achieved, and the incidence of side effects after oral administration of papaverine hydrochloride as a soft gelatin capsule, were compared to those of a sustained release formulation. The incidence of side effects observed after 150 mg, two or three times per day, of the soft gelatin capsule was similar to that observed after 150 mg, twice per day, of the sustained release form in 15 patients with arteriosclerosis obliterans. A relatively higher plasma papaverine concentration was achieved, 120 minutes after 150 mg administration of the soft gelatin form, compared to an equivalent dose of the sustained release form. The degree of vasodilation obtained after four doses (150 mg X 4) of soft gelatin within 24 hrs., was significantly superior than that induced after four doses (150 mg X 4) of the sustained release form in 6 patients with a severe degree of arteriosclerosis obliterans.

Pharmacokinetics of papaverine in man

A retrospective pharmacokinetic analysis was done of papaverine plasma level data in man reported in the literature. Upon i.v. administration the plasma level vs time curve can best be described by an open two-compartment model, and upon p.o. administration by open-compartment model. The biological half-life of papaverine varies between 1.5 and 2.2 hours, and has a volume of distribution of approximately 15% of the body weight. Papaverine is practically completely metabolized and underlies the first-pass effect upon p.o. administration.

Papaverine hydrochloride: the evaluation of two new dosage forms

The bioavailability of papaverine, administered as sustained release capsules, an elixir, and soft gelatin capsules, was studied with volunteers. Blood samples were assayed for papaverine, using a gas chromatographic method, following the administration of single 150 mg doses of papaverine HC1. The elixir and the soft gelatin capsule resulted in nearly identical papaverine blood levels, while peak levels, area under the blood level-time curve, and plasma levels 0.5, 1.0, 1.5, and 2.0 hours after dosing with the sustained release capsule were significantly (p less than 0.01) lower.

Determination of papaverine in blood samples by gas-liquid chromatography and mass fragmentography

The measurement of papaverine in blood samples by using either a glass capillary column with a flame-ionization detector or a packed column with mass fragmentographic detection is described. The two methods permit the determination of the normal range of concentrations of papaverine in blood (2-500 ng/ml). Owing to its high specificity, mass fragmentography is greatly superior to capillary chromatography, which is sometimes subject to interferences by solvent impurities.

Serum binding of quinidine in experimental acute renal failure

Quinidine serum binding is increased in some patients with acute renal failure, but in animals with renal failure conflicting results were published. Therefore, serum binding of quinidine, papaverine and phenylbutazone was studied by equilibrium dialysis in rabbits and rats with acute renal failure induced either by injection of uranyl nitrate or ligation of the ureters. From the results it appears that, in animals, quinidine binding changes are different according to the model used for induction of the renal failure, regardless of the species studied. After ligation of the ureters, lipoprotein concentration increases, but the meaning of this increase for increased serum quinidine binding is not clear.

Influence of acute renal failure on the protein binding of drugs in animals and in man

Serum protein binding of phenylbutazone has been measured in the rat, guinea pig, cat, rabbit and dog, and the influence on it of renal failure induced by uranyl nitrate injection has been studied. In all speciies a clearcut decrease in binding was observed after the occurrence of renal failure; the time course of the fall in binding correlated well with development of renal failure. In further experiments, serum protein binding of two acidic drugs (phenylbutazone, warfarin), two basic drugs (papaverine, quinidine) and one neutral drug (digitoxin) was studied in rabbits with experimental renal failure, and the results compared with those obtained in patients with acute renal failure. In the rabbits, a decrease in the binding of phenylbutazone, warfarin, papaverine and quinidine was found, whereas protein binding of digitoxin was unchanged. In man, there was a definite fall in protein binding of phenylbutazone and digitoxin, a small decrease for warfarin and papaverine, and a slight increase for quinidine.

Gas-chromatographic measurement of codeine and norcodeine in human plasma

A gas-chromatographic method is described for determination of codeine and norcodeine in human plasma. The method is specific, sensitive, and precise. It was developed for use in bioavailability studies of therapeutic doses of codeine sulfate. After ingestion of a 60-mg codeine sulfate tablet, mean peak codeine concentration in plasma was 107 mug/liter at 1.0 hour. No measurable concentration of norcodeine was found in the plasma by this method.

Metabolism of papaverine. II. Species differences

1. The urinary and biliary excretion of radioactive products in a 6 hr period after intravenous administration of [3H]papaverine was studied in rat, guinea-pig, rabbit, cat and dog. All species excreted metabolites extensively in the bile; only in rabbit and guinea-pig is urinary excretion important. 2. Metabolites in urine and bile of all species studied are mainly monophenolic compounds conjugated to glucuronic or sulphuric acid. Differences in the excretion patterns of the metabolites between different species are only quantitative. 3. Blood or plasma levels of papaverine after intravenous injection decreased with half-lives of approximately 12, 15, 22, 60 and 60 min for rabbit, rat, guinea-pig, cat and dog, respectively. The metabolites disappeared much more slowly than papaverine from the plasma. 4. Binding of papaverine to plasma proteins, as studied by equilibrium dialysis, was more than 90% in all species.