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Mechanism of Action
Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d/l-amphetamine). Drugs of this class used in obesity are commonly known as “anorectics” or “anorexigenics.” The effect of phentermine on chronic weight management is likely mediated by release of catecholamines in the hypothalamus, resulting in reduced appetite and decreased food consumption, but other metabolic effects may also be involved. The exact mechanism of action is not known.
The precise mechanism of action of topiramate on chronic weight management is not known. Topiramate's effect on chronic weight management may be due to its effects on both appetite suppression and satiety enhancement, induced by a combination of pharmacologic effects including augmenting the activity of the neurotransmitter gamma-aminobutyrate, modulation of voltage-gated ion channels, inhibition of AMPA/kainite excitatory glutamate receptors, or inhibition of carbonic anhydrase.
Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.
The effect of Qsymia on the QTc interval was evaluated in a randomized, double-blind, placebo- and activecontrolled (400 mg moxifloxacin), parallel group/crossover thorough QT/QTc study. A total of 54 healthy subjects were administered Qsymia 7.5 mg/46 mg at steady state and then titrated to Qsymia 22.5 mg/138 mg at steady state. Qsymia 22.5 mg/138 mg [a supra-therapeutic dose resulting in a phentermine and topiramate maximum concentration (Cmax) of 4- and 3- times higher than those at Qsymia 7.5 mg/46 mg, respectively] did not affect cardiac repolarization as measured by the change from baseline in QTc.
Upon oral administration of a single Qsymia 15 mg/92 mg, the resulting mean plasma phentermine maximum concentration (Cmax), time to Cmax (Tmax), area under the concentration curve from time zero to the last time with measureable concentration (AUC0-∞), and area under the concentration curve from time zero to infinity (AUC0-t) are 49.1 ng/mL, 6 hr, 1990 ng•hr/mL, and 2000 ng•hr/mL, respectively. A high fat meal does not affect phentermine pharmacokinetics for Qsymia 15 mg/92 mg. Phentermine pharmacokinetics is approximately dose-proportional from Qsymia 3.75 mg/23 mg to phentermine 15 mg/topiramate 100 mg. Upon dosing phentermine/topiramate 15/100 mg fixed dose combination capsule to steady state, the mean phentermine accumulation ratios for AUC and Cmax are both approximately 2.5.
Upon oral administration of a single Qsymia 15 mg/92 mg, the resulting mean plasma topiramate Cmax, Tmax, AUC0-t, and AUC0-∞, are 1020 ng/mL, 9 hr, 61600 ng•hr/mL, and 68000 ng•hr/mL, respectively. A high fat meal does not affect topiramate pharmacokinetics for Qsymia 15 mg/92 mg. Topiramate pharmacokinetics is approximately dose-proportional from Qsymia 3.75 mg/23 mg to phentermine 15 mg/topiramate 100 mg. Upon dosing phentermine 15 mg/topiramate 100 mg fixed dose combination capsule to steady state, the mean topiramate accumulation ratios for AUC and Cmax are both approximately 4.0.
Phentermine is 17.5% plasma protein bound. The estimated phentermine apparent volume of distribution (Vd/F) is 348 L via population pharmacokinetic analysis.
Topiramate is 15 - 41% plasma protein bound over the blood concentration range of 0.5 to 250 μg/mL. The fraction bound decreased as blood topiramate increased. The estimated topiramate Vc/F (volume of the central compartment), and Vp/F (volume of the peripheral compartment) are 50.8 L, and 13.1 L, respectively, via population pharmacokinetic analysis.
Metabolism and Excretion
Phentermine has two metabolic pathways, namely p-hydroxylation on the aromatic ring and N-oxidation on the alipthatic side chain. Cytochrome P450 (CYP) 3A4 primarily metabolizes phentermine but does not show extensive metabolism. Monoamine oxidase (MAO)-A and MAO-B do not metabolize phentermine. Seventy to 80% of a dose exists as unchanged phentermine in urine when administered alone. The mean phentermine terminal half-life is about 20 hours. The estimated phentermine oral clearance (CL/F) is 8.79 L/h via population pharmacokinetic analysis.
Topiramate does not show extensive metabolism. Six topiramate metabolites (via hydroxylation, hydrolysis, and glucuronidation) exist, none of which constitutes more than 5% of an administered dose. About 70% of a dose exists as unchanged topiramate in urine when administered alone. The mean topiramate terminal half-life is about 65 hours. The estimated topiramate CL/F is 1.17 L/h via population pharmacokinetic analysis.
A single-dose, open-label study was conducted to evaluate the pharmacokinetics of Qsymia 15 mg/92 mg in patients with varying degrees of chronic renal impairment compared to healthy volunteers with normal renal function. The study included patients with renal impairment classified on the basis of creatinine clearance as mild (greater or equal to 50 and less than 80 mL/min), moderate (greater than or equal to 30 and less than 50 mL/min), and severe (less than 30 mL/min). Creatinine clearance was estimated from serum creatinine based on the Cockcroft-Gault equation.
Compared to healthy volunteers, phentermine AUC0-inf was 91%, 45%, and 22% higher in patients with severe, moderate, and mild renal impairment, respectively; phentermine Cmax was 2% to 15% higher. Compared to healthy volunteers, topiramate AUC0-inf was 126%, 85%, and 25% higher for patients with severe, moderate, and mild renal impairment, respectively; topiramate Cmax was 6% to 17% higher. An inverse relationship between phentermine or topiramate Cmax or AUC and creatinine clearance was observed.
A single-dose, open-label study was conducted to evaluate the pharmacokinetics of Qsymia 15 mg/92 mg in healthy volunteers with normal hepatic function compared with patients with mild (Child-Pugh score 5 - 6) and moderate (Child-Pugh score 7 - 9) hepatic impairment. In patients with mild and moderate hepatic impairment, phentermine AUC was 37% and 60% higher compared to healthy volunteers. Pharmacokinetics of topiramate was not affected in patients with mild and moderate hepatic impairment when compared with healthy volunteers. Qsymia has not been studied in patients with severe hepatic impairment (Child-Pugh score 10 - 15) [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS, and Use In Specific Populations].
In Vitro Assessment of Drug Interactions
Phentermine is not an inhibitor of CYP isozymes CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4, and is not an inhibitor of monoamine oxidases. Phentermine is not an inducer of CYP1A2, CYP2B6, and CYP3A4. Phentermine is not a P-glycoprotein substrate.
Topiramate is not an inhibitor of CYP isozymes CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6, CYP2E1, and CYP3A4/5. However, topiramate is a mild inhibitor of CYP2C19. Topiramate is a mild inducer of CYP3A4. Topiramate is not a P-glycoprotein substrate.
Effects of Phentermine/Topiramate on Other Drugs
Table 6: Effect of Phentermine/Topiramate on the
Pharmacokinetics of Co-administered Drugs
|Phentermine/Topiramate||Co-administered Drug and Dosing Regimen|
|Drug and Dose (mg)||Change in AUC||Change in Cmax|
|*15 mg/92 mg dose QD for 16 days||Metformin 500 mg BID for 5 days||↑23%||↑16%|
|*15 mg/92 mg dose QD for 21 days||Sitagliptin 100 mg QD for 5 days||↓ 3%||↓9%|
|15 mg/92 mg dose QD for 15 days||Oral contraceptive single dose norethindrone 1 mg ethinyl estradiol 35 mcg||↑16%
|*A single study examined the effect of multiple-dose Qsymia 15 mg/92 mg once daily on the pharmacokinetics of multiple-dose 500 mg metformin twice daily and multiple-dose 100 mg sitagliptin once daily in 10 men and 10 women (mean BMI of 27.1 kg/m² and range of 22.2 – 32.7 kg/m²). The study participants received metformin, sitagliptin, phentermine/topiramate only, phentermine/topiramate plus probenecid, phentermine/topiramate plus metformin, and phentermine/topiramate plus sitagliptin on Days 1 – 5, 6 – 10, 11 – 28, 29, 30 – 34, and 35 – 39, respectively.|
Effect of Other Drugs on Phentermine/Topiramate
Table 7: Effect of Co-administered Drugs on the
Pharmacokinetics of Phentermine/Topiramate
|Co-administered Drug and Dosing Regimen||Phentermine/Topiramate|
|Dose (mg)||Change in AUC||Change in Cmax|
|Topiramate 92 mg single dose||15 mg phentermine single dose||↑42%||↑ 13%|
|Phentermine 15 mg single dose||92 mg topiramate single dose||↑6%||↑2%|
|*Metformin 500 mg BID for 5 days||15 mg/92 mg dose QD for 16 days phentermine topiramate||↑ 5%||↑7%|
|↓ 5%||↓ 4%|
|*Sitagliptin 100 mg QD for 5 days||15 mg/92 mg dose QD for 21 days phentermine topiramate||↑9%||↑10%|
|*Probenecid 2 g QD||15 mg/92 mg dose QD for 11 days phentermine topiramate||↓0.3%
|*The same single study examined the effect of multiple-dose 500 mg metformin twice daily, a single-dose 2 g probenecid, and multiple-dose 100 mg sitagliptin once daily on the pharmacokinetics of multiple-dose phentermine/topiramate 15 mg/92 mg once daily in 10 men and 10 women (mean BMI of 27.1 kg/m² and range of 22.2 – 32.7 kg/m²). The study participants received metformin, sitagliptin, phentermine/topiramate only, phentermine/topiramate plus probenecid, phentermine/topiramate plus metformin, and phentermine/topiramate plus sitagliptin on Days 1 – 5, 6 – 10, 11 – 28, 29, 30 – 34, and 35 – 39, respectively.|
Effects of Topiramate Alone on Other Drugs and Effects of Other Drugs on Topiramate
Potential interactions between topiramate and standard antiepileptic (AED) drugs were assessed in controlled clinical pharmacokinetic studies in patients with epilepsy. The effects of these interactions on mean plasma AUCs are summarized in Table 8.
In Table 8, the second column (AED concentration) describes what happens to the concentration of the AED listed in the first column when topiramate is added. The third column (topiramate concentration) describes how the co-administration of a drug listed in the first column modifies the concentration of topiramate in experimental settings when topiramate was given alone.
Table 8: Summary of AED Interactions with Topiramate
|AED Co-administered||AED Concentration||Topiramate Concentration|
|Phenytoin||NC or 25% increasea||48% decrease|
|Carbamazepine (CBZ)||NC||40% decrease|
|Valproic acid||11% decrease||14% decrease|
|Lamotrigine||NC at TPM doses up to 400 mg/day||13% decrease|
|a Plasma concentration increased 25% in some
patients, generally those on a twice a day dosing regimen of phenytoin.
b Is not administered but is an active metabolite of carbamazepine.
NC = Less than 10% change in plasma concentration; NE = Not Evaluated; TPM = topiramate
In a single-dose study, serum digoxin AUC was decreased by 12% with concomitant topiramate administration. The clinical relevance of this observation has not been established.
A drug-drug interaction study conducted in healthy volunteers evaluated the steady-state pharmacokinetics of hydrochlorothiazide (HCTZ) (25 mg q24h) and topiramate (96 mg q12h) when administered alone and concomitantly. The results of this study indicate that topiramate Cmax increased by 27% and AUC increased by 29% when HCTZ was added to topiramate. The clinical significance of this change is unknown. The steadystate pharmacokinetics of HCTZ were not significantly influenced by the concomitant administration of topiramate. Clinical laboratory results indicated decreases in serum potassium after topiramate or HCTZ administration, which were greater when HCTZ and topiramate were administered in combination.
A drug-drug interaction study conducted in healthy volunteers evaluated the steady-state pharmacokinetics of topiramate and pioglitazone when administered alone and concomitantly. A 15% decrease in the area under the concentration-time curve during a dosage interval at steady state (AUCτ,ss) of pioglitazone with no alteration in maximum steady-state plasma drug concentration during a dosage interval (Cmax,ss) was observed. This finding was not statistically significant. In addition, a 13% and 16% decrease in Cmax,ss and AUCτ,ss respectively, of the active hydroxy-metabolite was noted as well as a 60% decrease in Cmax,ss and AUCτ,ss of the active keto-metabolite. The clinical significance of these findings is not known. When topiramate is added to pioglitazone therapy or pioglitazone is added to topiramate therapy, careful attention should be given to the routine monitoring of patients for adequate control of their diabetic disease state.
A drug-drug interaction study conducted in patients with type 2 diabetes evaluated the steady-state pharmacokinetics of glyburide (5 mg/day) alone and concomitantly with topiramate (150 mg/day). There was a 22% decrease in Cmax and a 25% reduction in AUC24 for glyburide during topiramate administration. Systemic exposure (AUC) of the active metabolites, 4-trans-hydroxyglyburide (M1) and 3-cis-hydroxyglyburide (M2), was reduced by 13% and 15%, and Cmax was reduced by 18% and 25%, respectively. The steady-state pharmacokinetics of topiramate were unaffected by concomitant administration of glyburide.
In patients, the pharmacokinetics of lithium were unaffected during treatment with topiramate at doses of 200 mg/day; however, there was an observed increase in systemic exposure of lithium (27% for Cmax and 26% for AUC) following topiramate doses up to 600 mg/day. Lithium levels should be monitored when co-administered with high-dose topiramate.
The pharmacokinetics of a single dose of haloperidol (5 mg) were not affected following multiple dosing of topiramate (100 mg every 12 hours) in 13 healthy adults (6 males, 7 females).
There was a 12% increase in AUC and Cmax for amitriptyline (25 mg per day) in 18 normal subjects (9 males, 9 females) receiving 200 mg/day of topiramate. Some subjects may experience a large increase in amitriptyline concentration in the presence of topiramate and any adjustments in amitriptyline dose should be made according to the patient's clinical response and not on the basis of plasma levels.
Multiple dosing of topiramate (100 mg every 12 hrs) in 24 healthy volunteers (14 males, 10 females) did not affect the pharmacokinetics of single-dose sumatriptan either orally (100 mg) or subcutaneously (6 mg).
When administered concomitantly with topiramate at escalating doses of 100, 250, and 400 mg/day, there was a reduction in risperidone systemic exposure (16% and 33% for steady-state AUC at the 250 and 400 mg/day doses of topiramate). No alterations of 9-hydroxyrisperidone levels were observed. Co-administration of topiramate 400 mg/day with risperidone resulted in a 14% increase in Cmax and a 12% increase in AUC12 of topiramate. There were no clinically significant changes in the systemic exposure of risperidone plus 9-hydroxyrisperidone or of topiramate; therefore, this interaction is not likely to be of clinical significance.
Multiple dosing of topiramate (200 mg/day) in 34 healthy volunteers (17 males, 17 females) did not affect the pharmacokinetics of propranolol following daily 160 mg doses. Propranolol doses of 160 mg/day in 39 volunteers (27 males, 12 females) had no effect on the exposure to topiramate, at a dose of 200 mg/day of topiramate.
Multiple dosing of topiramate (200 mg/day) in 24 healthy volunteers (12 males, 12 females) did not affect the pharmacokinetics of a 1 mg subcutaneous dose of dihydroergotamine. Similarly, a 1 mg subcutaneous dose of dihydroergotamine did not affect the pharmacokinetics of a 200 mg/day dose of topiramate in the same study.
Co-administration of diltiazem (240 mg Cardizem CD®) with topiramate (150 mg/day) resulted in a 10% decrease in Cmax and a 25% decrease in diltiazem AUC, a 27% decrease in Cmax and an 18% decrease in desacetyl diltiazem AUC, and no effect on N-desmethyl diltiazem. Co-administration of topiramate with diltiazem resulted in a 16% increase in Cmax and a 19% increase in AUC12 of topiramate.
Multiple dosing of topiramate (150 mg/day) in healthy volunteers did not affect the pharmacokinetics of venlafaxine or O-desmethyl venlafaxine. Multiple dosing of venlafaxine (150 mg extended release) did not affect the pharmacokinetics of topiramate.
Reproductive and Developmental Toxicology
Topiramate, a component of Qsymia, causes developmental toxicity, including teratogenicity, in multiple animal species at clinically relevant doses.
When oral doses of 20, 100, or 500 mg/kg were administered to pregnant mice during the period of organogenesis, the incidence of fetal malformations (primarily craniofacial defects) was increased at all doses. The low dose of topiramate in this study (20 mg/kg) is approximately 2 times the MRHD of topiramate in Qsymia 15 mg/92 mg on a mg/m² basis. Fetal body weights and skeletal ossification were reduced at 500 mg/kg in conjunction with decreased maternal body weight gain.
In rat studies (oral doses of 20, 100, and 500 mg/kg or 0.2, 2.5, 30, and 400 mg/kg), the frequency of limb malformations (ectrodactyly, micromelia, and amelia) was increased among the offspring of dams treated with 400 mg/kg (34 times the MRHD of Qsymia based on AUC estimates) or greater during the organogenesis period of pregnancy. Embryotoxicity (reduced fetal body weights, increased incidence of structural variations) was observed at doses as low as 20 mg/kg (2 times the MRHD of Qsymia based on estimated AUC). Clinical signs of maternal toxicity were seen at 400 mg/kg and above, and maternal body weight gain was reduced during treatment with 100 mg/kg or greater.
In rabbit studies (20, 60, and 180 mg/kg or 10, 35, and 120 mg/kg orally during organogenesis), embryo/fetal mortality was increased at 35 mg/kg (2 times the MRHD based on estimated AUC) or greater, and teratogenic effects (primarily rib and vertebral malformations) were observed at 120 mg/kg (6 times the MRHD of Qsymia based on estimated AUC). Evidence of maternal toxicity (decreased body weight gain, clinical signs, and/or mortality) was seen at 35 mg/kg and above.
When female rats were treated during the latter part of gestation and throughout lactation (0.2, 4, 20, and 100 mg/kg or 2, 20, and 200 mg/kg), offspring exhibited decreased viability and delayed physical development at 200 mg/kg (16 times the MRHD of Qsymia based on estimated AUC) and reductions in pre-and/or post-weaning body weight gain at 2 mg/kg (2 times the MRHD of Qsymia based on estimated AUC) and above. Maternal toxicity (decreased body weight gain, clinical signs) was evident at 100 mg/kg or greater.
In a rat embryo/fetal development study with a postnatal component (0.2, 2.5, 30, or 400 mg/kg during organogenesis; noted above), pups exhibited delayed physical development at 400 mg/kg (34 times the MRHD of Qsymia based on estimated AUC) and persistent reductions in body weight gain at 30 mg/kg (2 times the MRHD of Qsymia based on estimated AUC) and higher.
The effect of Qsymia on weight loss in conjunction with reduced caloric intake and increased physical activity was studied in 2 randomized, double-blind, placebo controlled studies in obese patients (Study 1) and in obese and overweight patients with two or more significant co-morbidities (Study 2). Both studies had a 4-week titration period, followed by 52 weeks of treatment. There were 2 co-primary efficacy outcomes measured after 1 year of treatment (Week 56): 1) the percent weight loss from baseline; and 2) treatment response defined as achieving at least 5% weight loss from baseline.
In Study 1, obese patients (BMI greater than or equal to 35 kg/m²) were randomized to receive 1 year of treatment with placebo (N=514), Qsymia 3.75 mg/23 mg (N=241), or Qsymia 15 mg/92 mg (N=512) in a 2:1:2 ratio. Patients ranged in age from 18-71 years old (mean age 43) and 83% were female. Approximately 80% were Caucasian, 18% were African American, and 15% were Hispanic/Latino. At the beginning of the study the average weight and BMI of patients was 116 kg and 42 kg/m², respectively. Patients with type 2 diabetes were excluded from participating in Study 1. During the study, a well-balanced, reduced-calorie diet to result in an approximate 500 kcal/day decrease in caloric intake was recommended to all patients and patients were offered nutritional and lifestyle modification counseling.
In Study 2, overweight and obese patients were randomized to receive 1 year of treatment with placebo (N=994), Qsymia 7.5 mg/46 mg (N=498), or Qsymia 15 mg/92 mg (N=995) in a 2:1:2 ratio. Eligible patients had to have a BMI greater than or equal to 27 kg/m² and less than or equal to45 kg/m² (no lower limit on BMI for patients with type 2 diabetes) and two or more of the following obesity-related co-morbid conditions:
- Elevated blood pressure (greater than or equal to 140/90 mmHg, or greater than or equal to 130/85 mmHg for diabetics) or requirement for greater than or equal to 2 antihypertensive medications;
- Triglycerides greater than 200-400 mg/dL or were receiving treatment with 2 or more lipidlowering agents;
- Elevated fasting blood glucose (greater than100 mg/dL) or diabetes; and/or
- Waist circumference greater than or equal to 102 cm for men or greater than or equal to 88 cm for women).
Patients ranged in age from 19-71 years old (mean age 51) and 70% were female. Approximately 86% were Caucasian, 12% were African American, and 13.0% were Hispanic/Latino. The average weight and BMI of patients at the start of the study was 103 kg and 36.6 kg/m², respectively. Approximately half (53%) of patients had hypertension at the start of the study. There were 388 (16%) patients with type 2 diabetes at the start of the study. During the study, a well-balanced, reduced-calorie diet to result in an approximate 500 kcal/day decrease in caloric intake was recommended to all patients and patients were offered nutritional and lifestyle modification counseling.
A substantial percentage of randomized patients withdrew from each study prior to week 56, 40% in Study 1, and 31% in Study 2.
Table 9 provides the results for the weight loss at 1 year in Studies 1 and 2. After 1 year of treatment with Qsymia, all dose levels resulted in statistically significant weight loss compared to placebo (Table 9, Figures 1 and 2). A statistically significant greater proportion of the patients randomized to Qsymia than placebo achieved 5% and 10% weight loss.
Table 9: Weight Loss at One Year in Study 1 and 2
|Analysis Method||Study 1 (Obesity)||Study 2 (Overweight and Obese with Co-morbidities)|
|Placebo||Qsymia 3.75 mg/23 mg||Qsymia 15 mg/92 mg||Placebo||Qsymia 7.5 mg/46 mg||Qsymia 15 mg/92 mg|
|ITT-LOCF (Primary)*||n = 498||n = 234||n = 498||n = 979||n = 488||n =981|
|Baseline mean (SD)||115.7 (21.4)||118.6 (21.9)||115.2 (20.8)||103.3 (18.1)||102.8 (18.2)||103.1 (17.6)|
|% LS Mean Change from baseline (SE)**||-1.6 (0.4)||-5.1 (0.5)†||-10.9 (0.4)†,‡||-1.2 (0.3)||-7.8 (0.4)†||-9.8 (0.3)†,‡|
|Difference from placebo (95% CI)||3.5 (2.4-4.7)||9.4 (8.4-10.3)||6.6 (5.8-7.4)||8.6 (8.0-9.3)|
|Percentage of patients losing greater than or equal to 5% body weight||17%||45%f||67%†,‡||21%||62%†||70%†,‡|
|Risk Difference vs. placebo (95% CI)||27.6 (20.434.8)||49.4 (44.1-54.7)||41.3 (36.346.3)||49.2 (45.453.0)|
|Percentage of patients losing greater than or equal to 10% body weight||7%||19%†||47%†‡||7%||37%†||48%†‡|
|Risk Difference vs. placebo (95% CI)||11.4 (5.9-16.9)||39.8 (34.8-44.7)||29.9 (25.334.5)||40.3 (36.743.8)|
|SD=standard deviation; LS=least-squares; SE=standard
error; CI=confidence interval
* Uses all available data from subjects in ITT population, including data collected from subjects who discontinued drug but remained on study. LOCF method used to impute missing data.
† p < 0.0001 vs. placebo based on least-squares (LS) mean from an analysis of covariance.
‡ p < 0.01 vs. 3.75 mg/23 mg (Study 1) or 7.5 mg/46 mg (Study 2) dose.
Type 1 error was controlled across all pairwise treatment comparisons.
** Adjusted for baseline bodyweight (Study 1) and baseline bodyweight and diabetic status (Study 2)
Figure 1: Study 1 - Percent Weight Change & Figure
2: Study 2 - Percent Weight Change
The changes in cardiovascular, metabolic, and anthropometric risk factors associated with obesity from studies Study 1 and 2 are presented in Table 10 and 11. One year of therapy with Qsymia resulted in relative improvement over placebo in several risk factors associated with obesity with the exception of heart rate [see WARNINGS AND PRECAUTIONS].
Table 10: Least-Squares (LS) Mean† Change from
Baseline and Treatment Difference from Placebo in Risk Factors Following One
Year of Treatment in Study 1 (Obesity)
|Study 1 (Obesity)||Placebo
|Qsymia 3.75 mg/23 mg
|Qsymia 15 mg/92 mg
|Qsymia - Placebo: LS Mean|
|Qsymia 3.75 mg/23 mg||Qsymia 15 mg/92 mg|
|Heart rate, bpm|
|Baseline mean (SD)||73.2 (8.8)||72.3 (9.2)||73.1 (9.6)||+1.1||+1.8|
|LS Mean Change (SE)||-0.8 (0.5)||+0.3 (0.6)||+1.0 (0.5)|
|Systolic blood pressure, mmHg|
|Baseline mean (SD)||121.9 (11.5)||122.5 (11.1)||121.9 (11.6)||-2.8||-3.8|
|LS Mean Change (SE)||0.9 (0.6)||-1.8 (0.8)||-2.9 (0.6)|
|Diastolic blood pressure, mmHg|
|Baseline mean (SD)||77.2 (7.9)||77.8 (7.5)||77.4 (7.7)||-0.5||-1.9|
|LS Mean Change (SE)||0.4 (0.4)||-0.1 (0.6)||-1.5 (0.4)|
|Total Cholesterol, %|
|Baseline mean (SD)||194.3 (36.7)||196.3 (36.5)||192.7 (33.8)||-1.9||-2.5|
|LS Mean Change (SE)||-3.5 (0.6)||-5.4 (0.9)||-6.0 (0.6)|
|Baseline mean (SD)||120.9 (32.2)||122.8 (33.4)||120.0 (30.1)||-2.2||-2.8|
|LS Mean Change (SE)||-5.5 (1.0)||-7.7 (1.3)||-8.4 (0.9)|
|Baseline mean (SD)||49.5 (13.3)||50.0 (11.1)||49.7 (11.7)||+0.5||+3.5|
|LS Mean Change (SE)||+0.0 (0.8)||+0.5 (1.1)||+3.5 (0.8)|
|Baseline mean (SD)||119.0 (39.3)||117.5 (40.3)||114.6 (37.1)||-3.9||-14.3|
|LS Mean Change (SE)||+9.1 (2.3)||+5.2 (3.1)||-5.2 (2.2)|
|Fasting glucose, mg/dL|
|Baseline mean (SD)||93.1 (8.7)||93.9 (9.2)||93.0 (9.5)||-1.2||-2.5|
|LS Mean Change (SE)||+1.9 (0.5)||+0.8 (0.7)||-0.6 (0.5)|
|Waist Circumference, cm|
|Baseline mean (SD)||120.5 (14.0)||121.5 (15.2)||120.0 (14.7)||-2.5*||-7.8*|
|LS Mean Change (SE)||-3.1 (0.5)||-5.6 (0.6)||-10.9 (0.5)|
|SD=standard deviation; SE=standard error
* Statistically significant versus placebo based on the pre-specified method for controlling Type I error across multiple doses
† Study 1 adjusted for baseline bodyweight
Table 11: Least-Squares (LS) Mean† Change from Baseline
and Treatment Difference from Placebo in Risk Factors Following One Year of
Treatment in Study 2 (Overweight and Obese with Comorbidities)
|Study 2 (Overweight and Obese with Comorbidities)||Placebo
|Qsymia 7.5 mg/46 mg (N=488)||Qsymia 15 mg/92 mg (N=981)||Qsymia -Placebo: LS Mean|
|Qsymia 7.5 mg/46 mg||Qsymia 15 mg/92 mg|
|Heart rate, bpm|
|Baseline mean (SD)||72.1 (9.9)||72.2 (10.1)||72.6 (10.1)||+0.6||+1.7|
|LS Mean Change (SE)||-0.3 (0.3)||+0.3 (0.4)||+1.4 (0.3)|
|Systolic Blood Pressure, mmHg|
|Baseline mean (SD)||128.9 (13.5)||128.5 (13.6)||127.9 (13.4)||-2.3||-3.2|
|LS Mean Change (SE)||-2.4 (0.48)||-4.7 (0.63)||-5.6 (0.5)|
|Diastolic Blood Pressure, mmHg|
|Baseline mean (SD)||81.1 (9.2)||80.6 (8.7)||80.2 (9.1)||-0.7||-1.1|
|LS Mean Change (SE)||-2.7 (0.3)||-3.4 (0.4)||-3.8 (0.3)|
|Total Cholesterol, %|
|Baseline mean (SD)||205.8 (41.7)||201.0 (37.9)||205.4 (40.4)||-1.6||-3.0|
|LS Mean Change (SE)||-3.3 (0.5)||-4.9 (0.7)||-6.3 (0.5)|
|Baseline mean (SD)||124.2 (36.2)||120.3 (33.7)||123.9 (35.6)||+0.4||-2.8|
|LS Mean Change (SE)||-4.1 (0.9)||-3.7 (1.1)||-6.9 (0.9)|
|Baseline mean (SD)||48.9 (13.8)||48.5 (12.8)||49.1 (13.8)||+4.0||+5.6|
|LS Mean Change (SE)||+1.2 (0.7)||+5.2 (0.9)||+6.8 (0.7)|
|Baseline mean (SD)||163.5 (76.3)||161.1 (72.2)||161.9 (73.4)||-13.3||-15.3|
|LS Mean Change (SE)||+4.7 (1.7)||-8.6 (2.2)||-10.6 (1.7)|
|Fasting Insulin, (^IU/mL)|
|Baseline mean (SD)||17.8 (13.2)||18.0 (12.9)||18.4 (17.5)||-4.2||-4.7|
|LS Mean Change (SE)||+0.7 (0.8)||-3.5 (1.1)||-4.0 (0.8)|
|Fasting glucose, mg/dL|
|Baseline mean (SD)||106.6 (23.7)||106.2 (21.0)||105.7 (21.4)||-2.4||-3.6|
|LS Mean Change (SE)||+2.3 (0.6)||-0.1 (0.8)||-1.3 (0.6)|
|Waist Circumference, cm|
|Baseline mean (SD)||113.4 (12.2)||112.7 (12.4)||113.2 (12.2)||-5.2*||-6.8*|
|LS Mean Change (SE)||-2.4 (0.3)||-7.6 (0.4)||-9.2 (0.3)|
|SD=standard deviation; SE=standard error
* Statistically significant versus placebo based on the pre-specified method for controlling Type I error across multiple doses
† Study 2 adjusted for baseline bodyweight and diabetic status
Among the 388 subjects with type 2 diabetes treated in study 2, reductions in HbA1c from baseline (6.8%) were 0.1% for placebo compared to 0.4% and 0.4% with Qsymia 7.5 mg/46 mg and Qsymia 15 mg/92 mg, respectively. [see WARNINGS AND PRECAUTIONS].
Last reviewed on RxList: 4/8/2013
This monograph has been modified to include the generic and brand name in many instances.
Additional Qsymia Information
- Qsymia Drug Interactions Center: phentermine-topiramate oral
- Qsymia Side Effects Center
- Qsymia FDA Approved Prescribing Information including Dosage
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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