Fastin and Viagra drug interactions - a phase IV clinical study of FDA data

Summary:

Drug interactions are reported among people who take Fastin (phentermine hydrochloride) and Viagra (sildenafil citrate). Common drug interactions include adult respiratory distress syndrome among females and angina unstable among males.

The phase IV clinical study analyzes what interactions people have when they take Fastin and Viagra. It is created by eHealthMe based on reports of 6 people who take the same drugs from the FDA, and is updated regularly.

What is Fastin?

Fastin has active ingredients of phentermine hydrochloride. It is often used in weight loss. eHealthMe is studying from 2,168 Fastin users. Check the latest studies of Fastin.

What is Viagra?

Viagra has active ingredients of sildenafil citrate. It is often used in erection problems. eHealthMe is studying from 63,865 Viagra users. Check the latest studies of Viagra.

On Jun, 18, 2026

6 people who take Fastin and Viagra together, and have interactions are studied.

What are the common drug interactions of Fastin and Viagra, by gender? *:

female:

Adult respiratory distress syndrome (type of lung (pulmonary) failure)
Anaemia (lack of blood)
Blood carbon dioxide increased
Blood ph decreased
Dyspnoea (difficult or laboured respiration)
Heart rate decreased
Hypokalaemia (low potassium)
Hypophosphataemia (electrolyte disturbance in which there is an abnormally low level of phosphate in the blood)
Hypoxia (low oxygen in tissues)
Po2 decreased

male:

Angina unstable (chest pain due to ischemia of the heart muscle- unstable)
Drug withdrawal syndrome (interfere with normal social, occupational, or other functioning. are not due to another medical condition, drug use, or discontinuation)
Blister (small pocket of fluid within the upper layers of the skin caused by forceful rubbing (friction), burning, freezing, chemical exposure)
Drug abuser
Drug dependence
Multiple drug overdose
Pollakiuria (abnormally frequent passage of relatively small quantities or urine)
Sleep disorder
Appetite disorder (abnormal eating habits)
Chest discomfort

What are the common drug interactions of Fastin and Viagra, by age (0-1 to 60+)? *:

0-1:

n/a

2-9:

Angina pectoris (chest pain due to ischemia of the heart muscle)
Angina unstable (chest pain due to ischemia of the heart muscle- unstable)
Anorexia (eating disorder characterized by immoderate food restriction and irrational fear of gaining weight)
Blister (small pocket of fluid within the upper layers of the skin caused by forceful rubbing (friction), burning, freezing, chemical exposure)
Chest tightness
Dermatitis bullous (inflammation of the skin characterized by the presence of bullae which are filled with fluid)
Disease recurrence
Drug abuser
Drug dependence
Drug withdrawal syndrome (interfere with normal social, occupational, or other functioning. are not due to another medical condition, drug use, or discontinuation)

10-19:

n/a

20-29:

n/a

30-39:

n/a

40-49:

Angina unstable (chest pain due to ischemia of the heart muscle- unstable)
Drug withdrawal syndrome (interfere with normal social, occupational, or other functioning. are not due to another medical condition, drug use, or discontinuation)
Dyspnoea (difficult or laboured respiration)
Ear infection
Emotional distress
Hallucination, auditory (perceiving sounds without auditory stimulus)
Headache (pain in head)
Multiple drug overdose
Pollakiuria (abnormally frequent passage of relatively small quantities or urine)
Sinusitis (inflammation of sinus)

50-59:

Adult respiratory distress syndrome (type of lung (pulmonary) failure)
Anaemia (lack of blood)
Productive cough
Sputum abnormal
Tachycardia (a heart rate that exceeds the range of 100 beats/min)
Blood carbon dioxide increased
Blood ph decreased
Dyspnoea (difficult or laboured respiration)
Heart rate decreased
Hypokalaemia (low potassium)

60+:

n/a

* Approximation only. Some reports may have incomplete information.

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