CLINICAL PHARMACOLOGY
DDAVP (desmopressin acetate tablets) Tablets contain as active substance, desmopressin acetate, a synthetic analogue of the natural hormone arginine vasopressin.
Central Diabetes Insipidus: Dose response studies in patients with diabetes
insipidus have demonstrated that oral doses of 0.025 mg to 0.4 mg produced clinically
significant antidiuretic effects. In most patients, doses of 0.1 mg to 0.2 mg
produced optimal antidiuretic effects lasting up to eight hours. With doses
of 0.4 mg, antidiuretic effects were observed for up to 12 hours; measurements
beyond 12 hours were not recorded. Increasing oral doses produced dose dependent
increases in the plasma levels of DDAVP (desmopressin acetate).
The plasma half-life of DDAVP (desmopressin acetate tablets) followed a monoexponential time course with t1/2
values of 1.5 to 2.5 hours which was independent of dose.
The bioavailability of DDAVP (desmopressin acetate tablets) oral tablets is about 5% compared to intranasal
DDAVP (desmopressin acetate tablets) , and about 0.16% compared to intravenous DDAVP (desmopressin acetate tablets) . The time to reach maximum
plasma DDAVP (desmopressin acetate tablets) levels ranged from 0.9 to 1.5 hours following oral or intranasal
administration, respectively. Following administration of DDAVP (desmopressin acetate tablets) Tablets,
the onset of antidiuretic effect occurs at around 1 hour, and it reaches a maximum
at about 4 to 7 hours based on the measurement of increased urine osmolality.
The use of DDAVP (desmopressin acetate tablets) Tablets in patients with an established diagnosis will
result in a reduction in urinary output with an accompanying increase in urine
osmolality. These effects usually will allow resumption of a more normal life
style, with a decrease in urinary frequency and nocturia.
There are reports of an occasional change in response to the intranasal formulations
of DDAVP (desmopressin acetate tablets) (DDAVP (desmopressin acetate tablets) Nasal Spray and DDAVP (desmopressin acetate tablets) Rhinal Tube). Usually, the change occurred
over a period of time greater than six months. This change may be due to decreased
responsiveness, or to shortened duration of effect. There is no evidence that
this effect is due to the development of binding antibodies, but may be due
to a local inactivation of the peptide. No lessening of effect was observed
in the 46 patients who were treated with DDAVP (desmopressin acetate tablets) Tablets for 12 to 44 months
and no serum antibodies to desmopressin were detected.
The change in structure of arginine vasopressin to desmopressin acetate resulted
in less vasopressor activity and decreased action on visceral smooth muscle
relative to enhanced antidiuretic activity. Consequently, clinically effective
antidiuretic doses are usually below the threshold for effects on vascular or
visceral smooth muscle. In the four long-term studies of DDAVP (desmopressin acetate tablets) Tablets,
no increases in blood pressure in 46 patients receiving DDAVP (desmopressin acetate tablets) Tablets
for periods of 12 to 44 months were reported.
In one study, the pharmacodynamic characteristics of DDAVP (desmopressin acetate tablets) Tablets and
intranasal formulation were compared during an 8-hour dosing interval at steady
state. The doses administered to 36 hydrated (water loaded) healthy male adult
volunteers every 8 hours were 0.1, 0.2, 0.4 mg orally and 0.01 mg intranasally
by rhinal tube. The results are shown in the following table:
Mean Changes from Baseline (SE) in Pharmacodynamic Parameters
in Normal Healthy Adult Volunteers
Treatment |
Total Urine Volume
in mL |
Maximum Urine Osmolality in mOsm/kg |
0.1 mg PO q8h |
-3689.3 (149.6) |
514.8 (21.9) |
0.2 mg PO q8h |
-4429.9 (149.6) |
686.3 (21.9) |
0.4 mg PO q8h |
-4998.8 (149.6) |
769.3 (21.9) |
0.01 mg IN q8h |
-4844.9 (149.6) |
754.1 (21.9) |
(SE) = Standard error of the mean |
With respect to the mean values of total urine volume decrease and maximum urine osmolality increase from baseline, the 90% confidence limits estimated that the 0.4 mg and 0.2 mg oral dose produced between 95% and 110% and 84% to 99% of pharmacodynamic activity, respectively, when compared to the 0.01 mg intranasal dose.
While both the 0.2 mg and 0.4 mg oral doses are considered pharmacodynamically similar to the 0.01 mg intranasal dose, the pharmacodynamic data on an inter-subject basis was highly variable and, therefore, individual dosing is recommended.
In another study in diabetes insipidus patients, the pharmacodynamic characteristics
of DDAVP (desmopressin acetate tablets) Tablets and intranasal formulations were compared over a 12-hour
period. Ten fluid-controlled patients under age 18 were administered tablet
doses of 0.2 mg and 0.4 mg, and intranasal doses of 0.01 mg and 0.02 mg.
Mean Peak Pharmacodynamic Parameters (SD) in Pediatric and
Adolescent Diabetes Insipidus Patients
Treatment |
Urine Volume in mL/min |
Maximum Urine Osmolality in mOsm/kg |
0.01 mg IN |
0.3 (0.15) |
717.0 (224.63) |
0.02 mg IN |
0.3 (0.25) |
761.8 (298.82) |
0.2 mg PO |
0.3 (0.12) |
678.3 (147.91) |
0.4 mg PO |
0.2 (0.15) |
787.2 (73.34) |
(SD) = Standard Deviation |
All four dose formulations (0.01 mg IN, 0.02 mg IN, 0.2 mg PO and 0.4 mg PO) have a similar, pronounced pharmacodynamic effect on urine volume and urine osmolality. At two hours after study drug administration, mean urine volume was 4 mL/min and urine osmolality was >500 mOsm/kg. Mean plasma osmolality remained relatively constant over the time course recorded (0 to 12 hours). A statistical separation from baseline did not occur at any dose or time point. In these patients, the 0.2 mg tablets and the 0.01 mg intranasal spray exhibited similar pharmacodynamic profiles as did the 0.4 mg tablets and the 0.02 mg intranasal spray formulation. In another study of adult diabetes insipidus patients previously controlled on
DDAVP (desmopressin acetate tablets) intranasal spray, after one week of self-titration from spray to tablets,
patients' diuresis was controlled with 0.1 mg DDAVP (desmopressin acetate tablets) Tablets three times
a day.
Primary Nocturnal Enuresis: Two double-blind, randomized, placebo-controlled
studies were conducted in 340 patients with primary nocturnal enuresis. Patients
were 5-17 years old, and 72% were males. A total of 329 patients were evaluated
for efficacy. Patients were evaluated over a two-week baseline period in which
the average number of wet nights was 10 (range 4-14). Patients were then randomized
to receive 0.2, 0.4, or 0.6 mg of DDAVP (desmopressin acetate tablets) or placebo. The pooled results after
two weeks are shown in the following table:
Response to DDAVP (desmopressin acetate tablets) and Placebo at Two Weeks of Treatment Mean
(SE) Number of Wet Nights/2 Weeks
|
Placebo
(n = 85) |
0.2 mg/day
(n = 79) |
0.4 mg/day
(n = 82) |
0.6 mg/day
(n = 83) |
Baseline |
10 (0.3) |
11 (0.3) |
10 (0.3) |
10 (0.3) |
Reduction from Baseline |
1 (0.3) |
3 (0.4) |
3 (0.4) |
4 (0.4) |
Percent Reduction from Baseline |
10% |
27% |
30% |
40% |
p-value vs placebo |
---- |
<0.05 |
<0.05 |
<0.05 |
Patients treated with DDAVP (desmopressin acetate tablets) Tablets showed a statistically significant
reduction in the number of wet nights compared to placebo-treated patients.
A greater response was observed with increasing doses up to 0.6 mg.
In a six month, open-label extension study, patients completing the placebo-controlled studies were started on 0.2 mg/day DDAVP (desmopressin acetate tablets) , and the dose was progressively increased until the optimal response was achieved (maximum dose 0.6 mg/day). A total of 230 patients were evaluated for efficacy; the average number of wet nights/2 weeks during the untreated baseline period was 10 (range 4-14), and the average duration (SD) of treatment was 4.2 (1.8) months. Twenty-five (25) patients (11%) achieved a complete or near complete response ( ≤ 2 wet nights/2 weeks) and did not require titration to the 0.6 mg/day dose. The majority of patients (198 of 230, 86%) were titrated to the highest dose. When all dose groups were combined, 128 (56%) showed at least a 50% reduction from baseline in the number of wet nights/2 weeks, while 87 (38%) patients achieved a complete or near complete response.
Human Pharmacokinetics: DDAVP (desmopressin acetate tablets) is mainly excreted in the urine. A pharmacokinetic
study conducted in healthy volunteers and patients with mild, moderate, and
severe renal impairment (n=24, 6 subjects in each group) receiving single dose
desmopressin acetate (2mcg) injection demonstrated a difference in DDAVP (desmopressin acetate tablets) terminal
half-life. Terminal half-life significantly increased from 3 hours in normal
healthy patients to 9 hours in patients with severe renal impairment. (See CONTRAINDICATIONS.)