Not applicable.
Not applicable.
Non-clinical data revealed no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity and carcinogenic potential, toxicity to reproduction and development.
In pups of rats which were pre- and postnatally treated with 60 mg/kg sildenafil, a decreased litter size, a lower pup weight on day 1 and a decreased 4-day survival were seen at exposures which were approximately fifty times the expected human exposure at 20 mg three times a day. Effects in non-clinical studies were observed at exposures considered sufficiently in excess of the maximum human exposure indicating little relevance to clinical use.
There were no adverse reactions, with possible relevance to clinical use, seen in animals at clinically relevant exposure levels which were not also observed in clinical studies.
Non-clinical data revealed no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity, carcinogenic potential, and toxicity to reproduction and development.
Absorption
Sildenafil is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. The mean absolute oral bioavailability is 41 % (range 25-63 %). After oral three times a day dosing of sildenafil, AUC and Cmax increase in proportion with dose over the dose range of 20-40 mg. After oral doses of 80 mg three times a day a more than dose proportional increase in sildenafil plasma levels has been observed. In pulmonary arterial hypertension patients, the oral bioavailability of sildenafil after 80 mg three times a day was on average 43 % (90 % CI: 27 % -60 %) higher compared to the lower doses.
When sildenafil is taken with food, the rate of absorption is reduced with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29 % however, the extent of absorption was not significantly affected (AUC decreased by 11 %).
Distribution
The mean steady state volume of distribution (Vss) for sildenafil is 105 l, indicating distribution into the tissues. After oral doses of 20 mg three times a day, the mean maximum total plasma concentration of sildenafil at steady state is approximately 113 ng/ml. Sildenafil and its major circulating N-desmethyl metabolite are approximately 96 % bound to plasma proteins. Protein binding is independent of total drug concentrations.
Biotransformation
Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating metabolite results from N-demethylation of sildenafil. This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitro potency for PDE5 approximately 50 % that of the parent drug. The N-desmethyl metabolite is further metabolised, with a terminal half-life of approximately 4 h. In patients with pulmonary arterial hypertension, plasma concentrations of N-desmethyl metabolite are approximately 72 % those of sildenafil after 20 mg three times a day dosing (translating into a 36 % contribution to sildenafil's pharmacological effects). The subsequent effect on efficacy is unknown.
Elimination
The total body clearance of sildenafil is 41 l/h with a resultant terminal phase half-life of 3-5 h. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the faeces (approximately 80 % of administered oral dose) and to a lesser extent in the urine (approximately 13 % of administered oral dose).
Pharmacokinetics in special patient groups
Elderly
Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 90 % higher plasma concentrations of sildenafil and the active N-desmethyl metabolite compared to those seen in healthy younger volunteers (18-45 years). Due to age-differences in plasma protein binding, the corresponding increase in free sildenafil plasma concentration was approximately 40 %.
Renal insufficiency
In volunteers with mild to moderate renal impairment (creatinine clearance = 30-80 ml/min), the pharmacokinetics of sildenafil were not altered after receiving a 50 mg single oral dose. In volunteers with severe renal impairment (creatinine clearance < 30 ml/min), sildenafil clearance was reduced, resulting in mean increases in AUC and Cmax of 100 % and 88 % respectively compared to age-matched volunteers with no renal impairment. In addition, N-desmethyl metabolite AUC and Cmax values were significantly increased by 200 % and 79 % respectively in subjects with severe renal impairment compared to subjects with normal renal function.
Hepatic insufficiency
In volunteers with mild to moderate hepatic cirrhosis (Child-Pugh class A and B) sildenafil clearance was reduced, resulting in increases in AUC (85 %) and Cmax (47 %) compared to age-matched volunteers with no hepatic impairment. In addition, N-desmethyl metabolite AUC and Cmax values were significantly increased by 154 % and 87 %, respectively in cirrhotic subjects compared to subjects with normal hepatic function. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function have not been studied.
Population pharmacokinetics
In patients with pulmonary arterial hypertension, the average steady state concentrations were 20-50 % higher over the investigated dose range of 20-80 mg three times a day compared to healthy volunteers. There was a doubling of the Cmin compared to healthy volunteers. Both findings suggest a lower clearance and/or a higher oral bioavailability of sildenafil in patients with pulmonary arterial hypertension compared to healthy volunteers.
Paediatric population
From the analysis of the pharmacokinetic profile of sildenafil in patients involved in the paediatric clinical trials, body weight was shown to be a good predictor of drug exposure in children. Sildenafil plasma concentration half-life values were estimated to range from 4.2 to 4.4 hours for a range of 10 to 70 kg of body weight and did not show any differences that would appear as clinically relevant. Cmax after a single 20 mg sildenafil dose administered PO was estimated at 49, 104 and 165 ng/ml for 70, 20 and 10 kg patients, respectively. Cmax after a single 10 mg sildenafil dose administered PO was estimated at 24, 53 and 85 ng/ml for 70, 20 and 10 kg patients, respectively. Tmax was estimated at approximately 1 hour and was almost independent from body weight.
Absorption
Sildenafil is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. The mean absolute oral bioavailability is 41% (range 25-63%). After oral dosing of sildenafil AUC and Cmax increase in proportion with dose over the recommended dose range (25-100 mg).
When sildenafil is taken with food, the rate of absorption is reduced with a mean delay in tmax of 60 minutes and a mean reduction in Cmax of 29%.
Distribution
The mean steady state volume of distribution (Vd) for sildenafil is 105 l, indicating distribution into the tissues. After a single oral dose of 100 mg, the mean maximum total plasma concentration of sildenafil is approximately 440 ng/mL (CV 40%). Since sildenafil (and its major circulating N-desmethyl metabolite) is 96% bound to plasma proteins, this results in the mean maximum free plasma concentration for sildenafil of 18 ng/mL (38 nM). Protein binding is independent of total drug concentrations.
In healthy volunteers receiving sildenafil (100 mg single dose), less than 0.0002% (average 188 ng) of the administered dose was present in ejaculate 90 minutes after dosing.
Biotransformation
Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating metabolite results from N-demethylation of sildenafil. This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitro potency for PDE5 approximately 50% that of the parent drug. Plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil. The N-desmethyl metabolite is further metabolised, with a terminal half life of approximately 4 h.
Elimination
The total body clearance of sildenafil is 41 L/h with a resultant terminal phase half life of 3-5 h. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the faeces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of administered oral dose).
Pharmacokinetics in special patient groups
Elderly
Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 90% higher plasma concentrations of sildenafil and the active N-desmethyl metabolite compared to those seen in healthy younger volunteers (18-45 years). Due to age-differences in plasma protein binding, the corresponding increase in free sildenafil plasma concentration was approximately 40%.
Renal insufficiency
In volunteers with mild to moderate renal impairment (creatinine clearance = 30-80 mL/min), the pharmacokinetics of sildenafil were not altered after receiving a 50 mg single oral dose. The mean AUC and Cmax of the N-desmethyl metabolite increased up to 126% and up to 73% respectively, compared to age-matched volunteers with no renal impairment. However, due to high inter-subject variability, these differences were not statistically significant. In volunteers with severe renal impairment (creatinine clearance < 30 mL/min), sildenafil clearance was reduced, resulting in mean increases in AUC and Cmax of 100% and 88% respectively compared to age-matched volunteers with no renal impairment. In addition, N-desmethyl metabolite AUC and Cmax values were significantly increased by 200% and 79% respectively.
Hepatic insufficiency
In volunteers with mild to moderate hepatic cirrhosis (Child-Pugh A and B) sildenafil clearance was reduced, resulting in increases in AUC (84%) and Cmax (47%) compared to age-matched volunteers with no hepatic impairment. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function have not been studied.
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
It is recommended that a pharmacist constitutes Vimax (potency) oral suspension prior to its dispensing to the patient.
Reconstitution instructions
Note: A total volume of 90 ml (3 x 30 ml) of water irrespective of the dose to be taken should be used to reconstitute the contents of the bottle
1. Tap the bottle to release the powder.
2. Remove the cap.
3. Measure 30 ml of water by filling the measuring cup (included in the carton) to the marked line then pour the water into the bottle. Using the cup measure another 30 ml of water and add this to the bottle (figure 1).
4. Replace the cap and shake the bottle vigorously for a minimum of 30 seconds (figure 2).
5. Remove the cap.
6. Using the cup measure another 30 ml of water and add this to the bottle. You should always add a total of 90 ml (3 x 30 ml) of water irrespective of the dose you are taking (figure 3).
7. Replace the cap and shake the bottle vigorously for a minimum of 30 seconds (figure 4).
8. Remove the cap.
9. Press the bottle adaptor into the neck of the bottle (as shown on figure 5 below). The adaptor is provided so that you can fill the oral dosing syringe with medicine from the bottle. Replace the cap on the bottle.
10. When constituted the powder provides a white grape flavoured oral suspension. Write the date of expiry of the constituted oral suspension on the bottle label (the date of expiry of the constituted oral suspension is 30 days from the date of constitution). Any unused oral suspension should be discarded or returned to your pharmacist after this date.
Instructions for use
1. Shake the closed bottle of constituted oral suspension vigorously for a minimum of 10 seconds before use. Remove the cap (figure 6).
2. While the bottle is upright, on a flat surface, insert the tip of the oral dosing syringe into the adaptor (figure 7).
3. Turn the bottle upside down while holding the oral dosing syringe in place. Slowly pull back the plunger of the oral dosing syringe to the graduation mark that marks the dose for you (withdrawing 1 ml provides a 10 mg dose, withdrawing 2 ml provides a 20 mg dose). To measure the dose accurately, the top edge of the plunger should be lined up with the appropriate graduated mark on the oral dosing syringe (figure 8).
4. If large bubbles can be seen, slowly push the plunger back into the syringe. This will force the medicine back into the bottle. Repeat step 3 again.
5. Turn the bottle back upright with the oral dosing syringe still in place. Remove the oral dosing syringe from the bottle.
6. Put the tip of the oral dosing syringe into the mouth. Point the tip of the oral dosing syringe towards the inside of the cheek. SLOWLY push down the plunger of the oral dosing syringe. Do not squirt the medicine out quickly. If the medicine is to be given to a child, make sure the child is sitting, or is held, upright before giving the medicine (figure 9).
7. Replace the cap on the bottle, leaving the bottle adaptor in place. Wash the oral dosing syringe as instructed below.
Cleaning and storing the syringe:
1. The syringe should be washed after each dose. Pull the plunger out of the syringe and wash both parts in water.
2. Dry the two parts. Push the plunger back in to the syringe. Keep it in a clean safe place with the medicine.
Once reconstituted, the oral suspension should only be administered using the oral dosing syringe supplied with each pack. Refer to the patient leaflet for more detailed instructions for use.
No special requirements.
