Die Struktur von Tadalafil erlaubt eine selektive Bindung an die Bindungsstelle der PDE5 und minimiert gleichzeitig die Interaktion mit PDE6, was visuelle Nebenwirkungen einschränkt. Seine Verteilung im Organismus erfolgt breit, wobei das Verteilungsvolumen etwa 63 Liter beträgt. Über 90 % des Wirkstoffs sind an Plasmaproteine gebunden. Die Wirkung bleibt unabhängig von der Nahrungsaufnahme konstant. Der Abbauweg über CYP3A4 kann durch Hemmer wie Ritonavir oder Ketoconazol verlangsamt werden, was die Plasmakonzentrationen deutlich erhöht. In diesem Kontext wird cialis 20mg preis häufig in Bezug auf pharmakokinetische Wechselwirkungen erwähnt.

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Revision BulletinOfficial October 1, 2010 Tetracycline 1
Acceptance criteria: 90.0%–125.0%
Tetracycline Hydrochloride Capsules
PERFORMANCE TESTS
DEFINITION
Tetracycline Hydrochloride Capsules contain NLT 90.0% and Change to read:
NMT 125.0% of the labeled amount of C22H24N2O8 · HCl.
• DISSOLUTION 〈711〉
IDENTIFICATION
•Test 1• (RB 1-Oct-2010)
• The retention time of the major peak of the Sample solution Medium: Water; 900 mL
corresponds to that of the Standard solution, as obtained in Apparatus 2: 75 rpm; maintain a distance of 45 ± 5 mm
between the blade and the inside bottom of the vessel.
Time: 60 min; 90 min for 500-mg Capsules
Detector: UV 276 nm
• PROCEDURE
Standard solution: USP Tetracycline Hydrochloride RS in
Diluent: Dimethylformamide and 0.1 M ammonium oxalate
Sample solution: Pass a portion of the solution under test
Mobile phase: Dimethylformamide, 0.1 M ammonium oxa-
late, and 0.2 M dibasic ammonium phosphate (27:68:5).
Analysis: Determine the amount of C22H24N2O8 · HCl dis-
Adjust, if necessary, with 3 N ammonium hydroxide or 3 N solved by using UV absorption on portions of the Sample phosphoric acid to a pH of 7.6–7.7.
solution suitably diluted with Medium, if necessary, in com- Standard solution: 0.5 mg/mL of USP Tetracycline Hydro-
parison with a Standard solution having a known concentra- tion of USP Tetracycline Hydrochloride RS.
Sample solution: Equivalent to 0.5 mg/mL of tetracycline
Tolerances: NLT 80% (Q) of C22H24N2O8 · HCl is dissolved.
hydrochloride in Diluent from NLT 20 Capsules. [NOTE—Soni- •Test 2: If the product complies with this test, the labeling
indicates that the product meets USP Dissolution Test 2.
System suitability solution: 100 µg/mL of tetracycline hy-
Medium: Water; 900 mL, deaerated.
drochloride and 25 µg/mL of USP 4-Epianhydrotetracycline Apparatus 2: 75 rpm; maintain a distance of 45 ± 5 mm
between the blade and the inside bottom of the vessel.
Chromatographic system
(See Chromatography 〈621〉, System Suitability.) For Capsules labeled to contain 250 mg: 30 and 60 min For Capsules labeled to contain 500 mg: 30, 60, and 90 Detector: UV 280 nm
Guard column: 4.6-mm × 3-cm; 10-µm packing L7
Detector: UV 276 nm
Column: 4.6-mm × 25-cm; 5- to 10-µm packing L7
Standard solution: USP Tetracycline Hydrochloride RS in
Flow rate: 2 mL/min
System suitability
Sample solution: At the times specified, withdraw a known
Samples: Standard solution and System suitability solution
volume of the solution under test, and pass it through a [NOTE—The relative retention times of 4-epianhydrotetra- suitable filter. Dilute with Medium, if necessary. Replace the cycline and tetracycline are 0.9 and 1.0, respectively.] volume withdrawn with the same amount of Medium, pre- Suitability requirements
Resolution: NLT 1.2 between the 4-epianhydrotetra-
Blank: Medium
cycline and tetracycline peaks, System suitability solution Tolerances: See Tables 1 and 2.
Relative standard deviation: NMT 2.0%, Standard
Analysis
Samples: Standard solution and Sample solution
For Capsules Labeled to Contain 250 mg
Calculate the percentage of tetracycline hydrochloride Time (min)
Amount Dissolved
(C22H24N2O8 · HCl) in the portion of Capsules taken: Result = (rU/rS) × (CS/CU) × P × F × 100 = peak response of tetracycline from the Sample = peak response of tetracycline from the Standard For Capsules Labeled to Contain 500 mg
Time (min)
Amount Dissolved
= concentration of USP Tetracycline Hydrochloride RS in the Standard solution (mg/mL) = nominal concentration of the Sample solution = potency of USP Tetracycline Hydrochloride RS • UNIFORMITY OF DOSAGE UNITS 〈905〉: Meet the requirements
IMPURITIES
Organic Impurities
• PROCEDURE: LIMIT OF 4-EPIANHYDROTETRACYCLINE
Diluent, Mobile phase, Sample solution, Chromato-
graphic system, and System suitability: Proceed as di-
2010 The United States Pharmacopeial Convention All Rights Reserved. 2 Tetracycline
Standard solution: 10 µg/mL of USP 4-Epianhydrotetra-
ADDITIONAL REQUIREMENTS
cycline Hydrochloride RS in Diluent • PACKAGING AND STORAGE: Preserve in tight, light-resistant
Analysis
Samples: Standard solution and Sample solution
Calculate the percentage of 4-epianhydrotetracycline hy- Add the following:
drochloride in the portion of Capsules taken: • LABELING: When more than one Dissolution test is
U/rS) × (CS/CU) × F × 100 given, the labeling states the test used only if Test 1 is not = peak response of 4-epianhydrotetracycline from • USP REFERENCE STANDARDS 〈11〉
= peak response of 4-epianhydrotetracycline from USP 4-Epianhydrotetracycline Hydrochloride RS 2-Naphthacenecarboxamide, 4-(dimethylamino)- = concentration of USP 4-Epianhydrotetracycline 1,4,4a,5,12,12a-hexahydro-3,10,11,12a-tetrahydroxy-6- Hydrochloride RS in the Standard solution methyl-1,12-dioxo, monohydrochloride, [4R-(4α, 4aβ, = nominal concentration of tetracycline hydro- chloride in the Sample solution (mg/mL) (4S,4aS,5aS,6S,12aS)-4-(Dimethylamino)- Acceptance criteria: NMT 3.0%
1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a- pentahydroxy- 6-methyl-1,11-dioxo-2-naphthacenecarbox- SPECIFIC TESTS
• LOSS ON DRYING 〈731〉: Dry 100 mg of Capsule contents in a
capillary-stoppered bottle in vacuum at a pressure not ex- ceeding 5 mm of mercury at 60° for 3 h: it loses NMT 4.0% 2010 The United States Pharmacopeial Convention All Rights Reserved.

Source: http://www.usp.org/sites/default/files/usp_pdf/EN/tETRACYCLINEHYDROCHLORIDECAPSULES-M81820.pdf