CLINICAL PHARMACOLOGY
Mechanism Of Action
Nitazoxanide is an antiprotozoal [ see Microbiology].
Pharmacokinetics
Absorption
Single Dosing
Following oral administration of ALINIA Tablets or Oral
Suspension, the parent drug, nitazoxanide, is not detected in plasma. The
pharmacokinetic parameners of the metabolites, tizoxanide and tizoxanide glucuronide
are shown in Tables 2 and 3 below.
Table 2: Mean (+/- SD) plasma pharmacokinetic
parameters of tizoxanide and tizoxanide glucuronide following administration of
a single dose of one 500 mg ALINIA Tablet with food to subjects ≥12 years
of age
Age |
Tizoxanide |
Tizoxanide
Glucuronide |
Cmax (μg/mL) |
*Tmax (hr) |
AUC t (μg•hr/mL) |
C max (μg/mL) |
Tmax (hr) |
AUC t (μg•hr/mL) |
12 - 17 years |
9.1
(6.1) |
4.0
(1-4) |
39.5
(24.2) |
7.3
(1.9) |
4.0
(2-8) |
46.5
(18.2) |
> 18 years |
10.6
(2.0) |
3.0
(2-4) |
41.9
(6.0) |
10.5
(1.4) |
4.5
(4-6) |
63.0
(12.3) |
*Tmax is given as a Mean (Range) |
Table 3: Mean (+/-SD) plasma pharmacokinetic of tizoxanide and tizoxanide glucuronide parameter values following administration of single dose of ALINIA for Oral Suspension with food to subjects ≥1year of age
Age |
Dose |
Tizoxanide |
Tizoxanide Glucuronide |
max (μg/mL) |
*Tmax (hr) |
AUC t (μg•hr/mL) |
C max (μg/mL) |
*Tmax (hr) |
AUC inf (μg•hr/mL) |
1-3 years |
100 mg |
3.11
(2.0) |
3.5
(2-4) |
11.7
(4.46) |
3.64
(1.16) |
4.0
(3-4) |
19.0
(5.03) |
4-11 years |
200 mg |
3.00
(0.99) |
2.0
(1-4) |
13.5
(3.3) |
2.84
(0.97) |
4.0
(2-4) |
16.9
(5.00) |
> 18 years |
500 mg |
5.49
(2.06) |
2.5
(1-5) |
30.2
(12.3) |
3.21
(1.05) |
4.0
(2.56) |
22.8
(6.49) |
*Tmax is given as a Mean (Range) |
Multiple Dosing
Following oral administration of a single ALINIA Tablet
every 12 hours for 7 consecutive days, there was no significant accumulation of
nitazoxanide metabolites tizoxanide or tizoxanide glucuronide detected in
plasma.
Bioavailability
ALINIA for Oral Suspension is not bioequivalent to ALINIA
Tablets. The relative bioavailability of the suspension compared to the tablet
was 70%.
When ALINIA Tablets are administered with food, the AUCt
of tizoxanide and tizoxanide glucuronide in plasma is increased almost two-fold
and the Cmax is increased by almost 50%.
When ALINIA for Oral Suspension was administered with
food, the AUCt of tizoxanide and tizoxanide glucuronide increased by about
45-50% and the Cmax increased by ≥ 10%.
ALINIA Tablets and ALINIA for Oral Suspension were
administered with food in clinical trials and hence they are recomended to be
administered with food [see DOSAGE AND ADMINISTRATION]
Distribution
In plasma, more than 99% of tizoxanide is bound to
proteins.
Elimination
Metabolism
Following oral administration in humans, nitazoxanide is
rapidly hydrolyzed to an active metabolite, tizoxanide
(desacetyl-nitazoxanide). Tizoxanide then undergoes conjugation, primarily by glucuronidation.
Excretion
Tizoxanide is excreted in the urine, bile and feces, and
tizoxanide glucuronide is excreted in urine and bile. Approximately two-thirds
of the oral dose of nitazoxanide is excreted in the feces and one-third in the
urine.
Specific Populations
Pediatric Patients
The pharmacokinetics of tizoxanide and tizoxanide
glucuronide following administration of ALINIA Tablets in pediatric patients
12-17 years of age are provided above in Table 2. The pharmacokinetics of tizoxanide
and tizoxanide glucuronide following administration of ALINIA for Oral
Suspension in pediatric patients 1-11 years of age are provided above in Table
3.
Drug Interaction Studies
In vitro studies have demonstrated that tizoxanide has no
significant inhibitory effect on cytochrome P450 enzymes.
Microbiology
Mechanism Of Action
The antiprotozoal activity of nitazoxanide is believed to
be due to interference with the pyruvate:ferredoxin oxidoreductase (PFOR)
enzyme-dependent electron transfer reaction which is essential to anaerobic
energy metabolism. Studies have shown that the PFOR enzyme from G. lamblia directly
reduces nitazoxanide by transfer of electrons in the absence of ferredoxin. The
DNA-derived PFOR protein sequence of C. parvum appears to be similar to that of
G. lamblia. Interference with the PFOR enzyme-dependent electron transfer reaction
may not be the only pathway by which nitazoxanide exhibits antiprotozoal
activity.
Resistance
A potential for development of resistance by C. parvum or
G. lamblia to nitazoxanide has not been examined.
Antimicrobial Activity
Nitazoxanide and its metabolite, tizoxanide, are active in
vitro in inhibiting the growth of (i) sporozoites and oocysts of C. parvum
and (ii) trophozoites of G. lamblia.
Susceptibility Test Methods
For protozoa such as C. parvum and G. lamblia,
standardized tests for use in clinical microbiology laboratories are not
available.
Clinical Studies
Diarrhea Caused By G. Lamblia
Diarrhea Caused By G. Lamblia In Adults And Adoles Cents 12 Years Of Age Or Older:
In a double-blind, controlled trial (Study 1) conducted
in Peru and Egypt in adults and adolescents with diarrhea and with one or more
enteric symptoms (e.g., abdominal pain, nausea, vomiting, fever, abdominal
distention, loss of appetite, flatulence) caused by G. lamblia, a three-day
course of treatment with ALINIA Tablets administered 500 mg BID was compared
with a placebo tablet for 3 days. A third group of patients received open-label
ALINIA for Oral Suspension administered 500 mg/25 mL of suspension BID for 3
days. A second double-blind, controlled trial (Study 2) conducted in Egypt in adults
and adolescents with diarrhea and with or without enteric symptoms (e.g.,
abdominal colic, abdominal tenderness, abdominal cramps, abdominal distention,
fever, bloody stool) caused by G. lamblia compared ALINIA Tablets
administered 500 mg BID for 3 days to a placebo tablet. For both of these
studies, clinical response was evaluated 4 to 7 days following the end of
treatment. A clinical response of 'well' was defined as 'no symptoms, no watery
stools and no more than 2 soft stools with no hematochezia within the past 24
hours' or 'no symptoms and no unformed stools within the past 48 hours.' The
following clinical response rates were obtained:
Table 4: Adult and Adolescent Patients with Diarrhea
Caused by G. lamblia Clinical Response Rates* 4 to 7 Days Post-therapy %
(Number of Successes /Total)
|
ALINIA Tablets |
ALINIA for Oral Suspension |
Placebo Tablets |
Study 1 |
85% (46/54) ¶ § |
83% (45/54) ¶ § |
44% (12/27) |
Study 2 |
100% (8/8) |
- |
30% (3/10) |
* Includes all patients randomized with G. lamblia as the sole pathogen. Patients failing to complete the studies were treated as failures.
¶Clinical response rates statistically significantly higher when compared to
placebo.
§The 95% confidence interval of the difference in response rates for the tablet
and suspension is (- 14%, 17%). |
Some patients with 'well' clinical responses had G.
lamblia cysts in their stool samples 4 to 7 days following the end of
treatment. The relevance of stool examination results in these patients is
unknown. Patients should be managed based upon clinical response to treatment.
Diarrhea Caused By G. Lamblia In Pediatric Patients 1 Through 11 Years Of Age:
In a randomized, controlled trial conducted in Peru in
110 pediatric patients with diarrhea and with or without enteric symptoms
(e.g., abdominal distention, right iliac fossa tenderness) caused by G. lamblia,
a three-day course of treatment with nitazoxanide (100 mg BID in pediatric
patients ages 24-47 months, 200 mg BID in pediatric patients ages 4 through 11
years) was compared to a five-day course of treatment with metronidazole (125
mg BID in pediatric patients ages 2 through 5 years, 250 mg BID in pediatric
patients ages 6 through 11 years). Clinical response was evaluated 7 to 10 days
following initiation of treatment with a 'well' response defined as 'no
symptoms, no watery stools and no more than 2 soft stools with no hematochezia
within the past 24 hours' or 'no symptoms and no unformed stools within the
past 48 hours.' The following clinical cure rates were obtained:
Table 5: Clinical Response Rates in Pediatric Patients
7 to 10 Days Following Initiation of Therapy Intent-to-Treat and Per Protocol
Analyses % (Number of Successes /Total), [95% Confidence Interval]
Population |
Nitazoxanide (3 days) |
Metronidazole (5 days) |
95% CI Diff § |
Intent-to-treat analysis † |
85% (47/55) |
80% (44/55 ) |
[-9%, 20%] |
Per protocol analysis¶ |
90% (43/48) |
83% (39/47 ) |
[-8%, 21%] |
†Intent-to-treat analysis includes all patients
randomized with patients not completing the study treated as failures.
¶Per protocol analysis includes only patients who took all of their medication
and completed the study. Seven patients in each treatment group missed at least
one dose of medication and one in the metronidazole treatment group was lost to
follow-up.
§95% Confidence Interval on the difference in response rates
(nitazoxanide-metronidazole). |
Some patients with 'well' clinical responses had G.
lamblia cysts in their stool samples 4 to 7 days following the end of
treatment. The relevance of stool examination results in these patients is
unknown. Patients should be managed based upon clinical response to treatment.
Diarrhea Caused By C. Parvum
Diarrhea Caused By C. Parvum In Adults And Adolescents 12 Years Of Age Or Older:
In a double-blind, controlled trial conducted in Egypt in
adults and adolescents with diarrhea and with or without enteric symptoms
(e.g., abdominal pain/cramps, nausea, vomiting) caused by C. parvum, a
three day course of treatment with ALINIA Tablets administered 500 mg BID was
compared with a placebo tablet for 3 days. A third group of patients received
open-label ALINIA for Oral Suspension administered 500 mg/25 mL of suspension
BID for 3 days. Clinical response was evaluated 4 to 7 days following the end
of treatment. A clinical response of 'well' was defined as 'no symptoms, no
watery stools and no more than 2 soft stools within the past 24 hours' or 'no
symptoms and no unformed stools within the past 48 hours.' The following
clinical response rates were obtained:
Table 6: Clinical Response Rates in Adult and Adolescent
Patients 4 to 7 Days Post-therapy % (Number of Successes /Total)
|
ALINIA Tablets |
ALINIA Suspension |
Placebo Tablets |
Intent-to-treat analysis* |
96% (27/28)¶ § |
87% (27/31) ¶ § |
41% (1½7) |
*Includes all patients randomized with C. parvum as the
sole pathogen. Patients failing to complete the study were treated as failures.
¶Clinical response rates statistically significantly higher when compared to
placebo.
§The 95% confidence interval of the difference in response rates for the tablet
and suspension is (- 10%, 28%). |
In a second double-blind, placebo-controlled study of
nitazoxanide tablets conducted in Egypt in adults and adolescents with diarrhea
and with or without enteric symptoms (e.g., abdominal colic, abdominal cramps,
epigastric pain) caused by C. parvum as the sole pathogen, clinical and
parasitological response rates showed a similar trend to the first study.
Clinical response rates, evaluated 2 to 6 days following the end of treatment,
were 71% (15/21) in the nitazoxanide group and 42.9% (9/21) in the placebo
group.
Some patients with 'well' clinical responses had C.
parvum oocysts in their stool samples 4 to 7 days following the end of
treatment. The relevance of stool examination results in these patients is
unknown. Patients should be managed based upon clinical response to treatment.
Diarrhea Caused By C. Parvum In Pediatric Patients 1 Through 11 Years Of Age:
In two double-blind, controlled trials in pediatric
patients with diarrhea and with or without enteric symptoms (e.g., abdominal
distention, colic, left iliac fossa tenderness) caused by C. parvum, a
threeday course of treatment with nitazoxanide (100 mg BID in pediatric
patients ages 12-47 months, 200 mg BID in pediatric patients ages 4 through 11
years) was compared with a placebo. One study was conducted in Egypt in
outpatients ages 1 through 11 years with diarrhea caused by C. parvum.
Another study was conducted in Zambia in malnourished pediatric patients
admitted to the hospital with diarrhea caused by C. parvum. Clinical
response was evaluated 3 to 7 days post-therapy with a 'well' response defined
as 'no symptoms, no watery stools and no more than 2 soft stools within the
past 24 hours' or 'no symptoms and no unformed stools within the past 48
hours.' The following clinical response rates were obtained:
Table 7: Clinical Response Rates in Pediatric Patients
3 to 7 Days Post-therapy Intent-to-Treat Analyses % (Number of Successes
/Total)
Population |
Nitazoxanide* |
Placebo |
Outpatient Study, age 1 - 11 years |
88% (21/24) |
38% (9/24) |
Inpatient Study, Malnourished ¶, age 12-35 months |
56% (14/25) |
23% (5/22 ) |
*Clinical response rates statistically significantly
higher compared to placebo.
¶60% considered severely underweight, 19% moderately underweight, 17% mild
underweight. |
Some patients with 'well' clinical responses had C.
parvum oocysts in their stool samples 3 to 7 days following the end of
treatment. The relevance of stool examination results in these patients is
unknown. Â Patients should be managed based upon clinical response to treatment.
Diarrhea Caused By C. Parvum In Acquired Immune Deficiency Syndrome (Aids) Patients
A double-blind, placebo-controlled trial did not produce
clinical cure rates that were significantly different from the placebo control
when conducted in hospitalized, severely malnourished pediatric patients with
acquired immune deficiency syndrome (AIDS) in Zambia. In this study, the
pediatric patients received a three day course of nitazoxanide suspension (100
mg BID in pediatric patients ages 12-47 months, 200 mg BID in pediatric
patients ages 4 through 11 years) and were evaluated for response four days
after the end of treatment.