A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Pah Indications, Dosage, Storage, Stability - Aminohippurate
Pah Indications, Dosage, Storage, Stability - Aminohippurate
INDICATIONS AND USAGE
Estimation of effective renal plasma flow.
Measurement of the functional capacity of the renal tubular secretory mechanism.
DOSAGE AND ADMINISTRATION
For intravenous use only
Clearance measurements using single injection technics are generally inaccurate,
particularly in the measurement of ERPF. For this reason, intravenous infusions
at fixed rates are used to sustain the plasma PAH concentration at the desired
level.
To measure ERPF, the concentration of PAH in the plasma should be maintained
at 2 mg per 100 mL, which can be achieved with a priming dose of 6 to 10 mg/kg
and an infusion dose of 10 to 24 mg/min.
As a research procedure for the measurement of Tm PAH , the plasma
level of PAH must be sufficient to saturate the capacity of the tubular secretory
cells. Concentrations of from 40 to 60 mg per 100 mL are usually necessary.
Technical details of these tests may be found in Smith 1 ; Wesson
2 ; Bauer 3 ; Pitts 4 ; and Schnurr. 5
Parenteral drug products should be inspected visually for particulate matter
and discoloration prior to use, whenever solution and container permit. NOTE:
The normal color range for this product is a colorless to yellow/brown solution.
The efficacy is not affected by color changes within this range.
Calculations
Effective Renal Plasma Flow (ERPF)
The clearance of PAH, which is extracted almost completely from the plasma
during its passage through the renal circulation, constitutes a measure of ERPF.
Hence:
| |
ERPF |
U PAH V
P PAH |
| Where |
U PAH |
= |
concentration of PAH
(mg/mL) in the urine |
| V |
= |
rate of urine excretion
(mL/min), and |
| P PAH |
= |
plasma concentration
of PAH (mg/mL). |
| Example: |
U PAH |
= |
8.0 mg/mL |
| V |
= |
1.5 mL/min |
| P PAH |
= |
0.02 mg/mL |
| ERPF |
= |
8.0 × 1.5
0.02 |
= |
600 mL/min. |
Based on PAH clearance studies, the normal values for ERPF are:
|
men
|
675 ± 150 mL/min
|
|
women
|
595 ± 125 mL/min.
|
Maximum Tubular Secretory
Mechanism (Tm PAH )
The quantity of PAH, secreted by the tubules (Tm PAH ) is given
by the difference between the total rate of excretion (U PAH V) and
the quantity filtered by the glomeruli (GFR × P PAH ). Hence:
Tm PAH = U PAH V - (GFR × P PAH × 0.83)
The factor, 0.83, corrects for that portion of PAH which is bound to plasma
protein and hence is unfilterable.
|
Example:
|
U PAH
|
= 9.55 mg/mL
|
|
V
|
= 16.68 mL/min
|
|
GFR
|
= 120 mL/min
|
|
P PAH
|
= 0.60 mg/mL
|
Then Tm PAH = 9.55 × 16.68 - (120 × 0.60
× 0.83) = 100 mg/min.
Average normal values of Tm PAH are 80-90 mg/min.
The value of the expression U PAH V, used in calculations of ERPF
and Tm PAH , may be found by determining the amount of PAH in a measured
volume of urine excreted within a specific period of time.
These calculations are based on a body surface area of 1.73 m 2 .
Corrections for variations in surface area are made by multiplying the values
obtained for ERPF and Tm PAH by 1.73/A, where A is the subject surface
area.
HOW SUPPLIED
No. 95 Aminohippurate Sodium, 20 percent sterile solution for intravenous
injection, is supplied as follows:
NDC 0006-3395-11 in 10 mL vials.
Storage
Avoid storage at temperatures below -20°C (-4°F) and above 40°C (104°F).
REFERENCES
- Smith, H. W.: Lectures on the kidney, University Extension Division, University
of Kansas, Lawrence, Kansas, 1943.
- Wesson, L. G., Jr.: "Physiology of the Human Kidney," New York, Grune &
Stratton, 1969, pp. 632-655.
- Bauer, J. D.; Ackermann, P. G.; Toro, G.: "Brays Clinical Laboratory Methods,"
ed. 7, St. Louis, Mosby, 1968.
- Pitts, R. F.: "Physiology of the Kidney and Body Fluids," ed. 2, Chicago,
Year Book Medical Publishers, 1968.
- Schnurr, E., Lahme, W., Kuppers, H.: Measurement of renal clearance of inulin
and PAH in the steady state without urine collection; Clinical Nephrology,
13 (1): (26-29), 1980.
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Last updated Apr 01, 2003
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