Benadryl and Plan b one-step drug interactions - a phase IV clinical study of FDA data

Summary:

Drug interactions are reported among people who take Benadryl (diphenhydramine hydrochloride) and Plan b one-step (levonorgestrel). Common drug interactions include menstruation irregular among females.

The phase IV clinical study analyzes what interactions people have when they take Benadryl and Plan b one-step. It is created by eHealthMe based on reports of 35 people who take the same drugs from the FDA, and is updated regularly.

What is Benadryl?

Benadryl has active ingredients of diphenhydramine hydrochloride. It is often used in allergies. eHealthMe is studying from 104,956 Benadryl users. Check the latest studies of Benadryl.

What is Plan b one-step?

Plan b one-step has active ingredients of levonorgestrel. It is often used in birth control. eHealthMe is studying from 36,276 Plan b one-step users. Check the latest studies of Plan b one-step.

eHealthMe: drug outcomes in the real world

eHealthMe runs one of the largest post-marketing drug safety studies in the world. We study millions of patients and 5,000 more each day. Our data-driven phase IV clinical trials have been referenced on 800+ peer-reviewed medical publications including The Lancet, Mayo Clinic Proceedings, and Nature. Tools to study our phase IV findings are available to the public, anonymous and free >>>.

On Sep, 03, 2026

35 people who take Benadryl and Plan b one-step together, and have interactions are studied.

Benadryl and Plan b one-step drug interactions.

What are the common drug interactions of Benadryl and Plan B One-Step, by gender? *:

female:

Menstruation irregular
Pelvic pain
Abdominal pain upper
Breast enlargement
Breast pain
Death
Dyspnoea (difficult or laboured respiration)
Menorrhagia (an abnormally heavy bleeding and prolonged menstrual period at regular intervals)
Metrorrhagia (uterine bleeding at irregular intervals)
Pregnancy after post coital contraception

male:

n/a

What are the common drug interactions of Benadryl and Plan B One-Step, by age (0-1 to 60+)? *:

0-1:

n/a

2-9:

n/a

10-19:

Vaginal haemorrhage (vaginal bleeding)
Headache (pain in head)
Menstruation irregular
Dysmenorrhoea (painful menstruation)
Nausea (feeling of having an urge to vomit)
Abdominal pain
Abdominal pain lower
Abdominal pain upper
Anxiety
Dizziness

20-29:

Menstruation irregular
Pelvic pain
Ankle fracture
Fatigue (feeling of tiredness)
Nausea (feeling of having an urge to vomit)
Vomiting

30-39:

Menstruation irregular
Abdominal distension
Breast enlargement
Dysmenorrhoea (painful menstruation)
Pelvic pain
Stevens-johnson syndrome (an immune-complex-mediated hypersensitivity disorder. it ranges from mild skin and mucous membrane lesions to a severe)
Vaginal discharge
Abdominal pain lower
Arthropod sting (arthropod bite)
Breast pain

40-49:

Menstruation irregular
Pregnancy after post coital contraception
Maternal exposure before pregnancy (use of substance before pregnancy)
Menorrhagia (an abnormally heavy bleeding and prolonged menstrual period at regular intervals)
Metrorrhagia (uterine bleeding at irregular intervals)
Musculoskeletal pain (pain affects the bones, muscles, ligaments, tendons, and nerves)
Nausea (feeling of having an urge to vomit)
Pelvic pain
Pneumonia
Rhabdomyolysis (a condition in which damaged skeletal muscle tissue breaks down)

50-59:

n/a

60+:

n/a

What are the existing conditions these people have? *

Hypersensitivity: 8 people, 22.86%
Seasonal Allergy (allergic condition due to certain season): 6 people, 17.14%
High Blood Pressure: 4 people, 11.43%
Asthma: 4 people, 11.43%
Stress And Anxiety: 3 people, 8.57%
Multiple Allergies (allergy to multiple agents): 3 people, 8.57%
Sleep Disorder: 2 people, 5.71%
Pain: 2 people, 5.71%
Nausea (feeling of having an urge to vomit): 2 people, 5.71%
Insomnia (sleeplessness): 2 people, 5.71%

* Approximation only. Some reports may have incomplete information.

Do you take Benadryl and Plan b one-step?

- Personalize this study to your gender, age, symptoms and drugs
- Predict drug outcomes for up to one year with AI
- Get an AI agent to monitor your drugs continuously