The Effect of Sildenafil and Tadalafil on Skeletal Muscle and Perceptual Fatigue

Study Overview
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Brief Summary
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This study is funded by the Moody Endowment. In this project, we will investigate the potential effect of skeletal muscle nitric oxide (NO) production on skeletal muscle anabolism, muscle strength, physical function, and body composition in older individuals. Further, we will determine whether augmentation of NO-mediated signaling reduces fatigue and fatigability.

Detailed Description
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The Investigators hypothesize that upregulation of skeletal muscle NO-cGMP mediated responses through phosphodiesterase (PDE) inhibition by sildenafil or tadalafil causes an acute anabolic response of skeletal muscle protein synthesis. NO is well-known to elicit vasodilation through stimulation of cGMP signaling, and NO-mediated changes in muscle perfusion may influence both skeletal muscle anabolism and perceptual fatigue. To measure skeletal muscle protein synthesis, we will infuse a stable isotope tracer of phenylalanine and measure its incorporation into skeletal muscle proteins following a dose of sildenafil, tadalafil, or placebo. The Investigators will also determine whether differences exist between men and women in response to PDE inhibition. As skeletal muscle NO-cGMP signaling has been implicated in fatigue responses, we will assess the acute effect of sildenafil and tadalafil on fatigue. Fatigue can be manifested both as a performance deficit at a local level (e.g., a reduced ability of skeletal muscle to produce power or force) as well as a subjective experience of lacking physical or mental energy. Accordingly, we will use more than one means (skeletal muscle performance, fatigue questionnaires, accelerometers) to study fatigue. The Investigators hypothesize that sildenafil or tadalafil will acutely reduce exercise-associated fatigability and skeletal muscle fatigue development

Official Title
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The Effect of Sildenafil and Tadalafil on Skeletal Muscle and Perceptual Fatigue.

Conditions
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Fatigue

Intervention / Treatment
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* Drug: Sildenafil
* Drug: tadalafil
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 50-60 years of age Ability to sign consent form (score>23 on the 30-item Mini Mental Status examination, MMSE) Stable body weight for at least three months. Exclusion Criteria: Physical dependence or frailty (impairment in any of the Activities of Daily Living (ADL), history of falls (>2/year) or significant weight loss in the past year). Pregnancy Significant heart, liver, kidney, blood or respiratory disease. Peripheral vascular disease. Diabetes mellitus or other untreated endocrine disease. Active cancer Use of nitrates. Recent (within 6 months) treatment with anabolic steroids, or corticosteroids. Alcohol or drug abuse. Severe depression (>5 on the 15-item Geriatric Depression Scale, GDS). Cardiac abnormalities such as cardiac shunt or previously diagnosed pulmonary hypertension. Systolic blood pressure <100 or>150, diastolic blood pressure <60 or 90>. This range is smaller than the acceptable range stated in the prescribing information for sildenafil/tadalafil (90/50 and <170/110).

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Subjects were assigned to one of 4 arms: Sildenafil (50mg/day) for weeks 0-4. Placebo for weeks 5-8. Tadalafil (10mg/day) for weeks 0-4. Placebo for weeks 5-8. Placebo for weeks 0-4. Sildenafil (50mg/day) for weeks 5-8. Placebo for weeks 0-4. Tadalafil (10mg/day) for weeks 5-8.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Sildenafil / Placebo<br>50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8. | Drug: Sildenafil<br>* 50 mg/day for 4 weeks<br>* Other names: Revatio;Drug: Placebo<br>* Placebo 1 capsule per day for four weeks.<br>|
| Active Comparator: Tadalafil / Placebo<br>10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8. | Drug: tadalafil<br>* 10 mg/day for 4 weeks.<br>* Other names: Adcirca;Drug: Placebo<br>* Placebo 1 capsule per day for four weeks.<br>|
| Active Comparator: Placebo / Sildenafil<br>Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8. | Drug: Sildenafil<br>* 50 mg/day for 4 weeks<br>* Other names: Revatio;Drug: Placebo<br>* Placebo 1 capsule per day for four weeks.<br>|
| Active Comparator: Placebo / Tadalafil<br>Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8. | Drug: tadalafil<br>* 10 mg/day for 4 weeks.<br>* Other names: Adcirca;Drug: Placebo<br>* Placebo 1 capsule per day for four weeks.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Placebo | Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks. | after 4 weeks of placebo | 
| Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Active Drug | Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks. | after 4 weeks of active drug | 
| Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Placebo | The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test after 4 weeks of placebo. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue. | after 4 weeks of placebo | 
| Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Active Drug | The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue. | after 4 weeks of active drug | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo | Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of placebo | 
| Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug. | Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of active drug | 
| Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo. | Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of placebo | 
| Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug | Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of active drug | 
| Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0. | Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 0 | 
| Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4. | Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 4 | 
| Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8. | Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 8 | 
| Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0. | Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 0 | 
| Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4. | Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 4 | 
| Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8. | Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry. | week 8 | 
| Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Placebo | Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of placebo | 
| Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Active Drug | Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. | after 4 weeks of active drug | 
| Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 0 | Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue. | Week 0 | 
| Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 4 | Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue. | week 4 | 
| Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 8 | Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue. | week 8 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Infusion, Anabolism, Upregulation, Accelerometer, Placebo, Nitrosylation, Fatigue, Fatigability, Surface Electromyography (sEMG), cyclic guanosine monophosphate (cGMP), Nitric Oxide (NO), NO-cGMP, Phosphodiesterase (PDE), Sildenafil, Tadalafil, Isotope