Benadryl contains the active ingredient diphenhydramine hydrochloride in the form of an injection. It functions as an antihistaminic agent. The injection is formulated as a sterile, nonpyrogenic solution for intravenous or deep intramuscular use, with a dosage strength of diphenhydramine hydrochloride 50 mg per mL. Key inactive ingredients include benzethonium chloride and possibly sodium hydroxide or hydrochloric acid for pH adjustment.

How should I use this medication?

This medication is injected into a vein or a muscle. It is usually given by your care team in a hospital or clinic setting. It may also be given at home.

If you get this medication at home, you will be taught how to prepare and give it. Use exactly as directed. Take it as directed on the prescription label at the same time every day. Keep taking it unless your care team tells you to stop.

It is important that you put your used needles and syringes in a special sharps container. Do not put them in a trash can. If you do not have a sharps container, call your pharmacist or care team to get one.

Talk to your care team about the use of this medication in children. While it may be given to children for selected conditions, precautions do apply.

People 65 years and older may have a stronger reaction and need a smaller dose.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

Where should I keep my medication?

Keep out of the reach of children and pets.

If you are using this medication at home, you will be instructed on how to store this medication. Throw away any unused medication after the expiration date on the label.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

• Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
• Sudden eye pain or change in vision such as blurry vision, seeing halos around lights, vision loss
• Trouble passing urine

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

• Constipation
• Drowsiness
• Dry mouth
• Headache
• Upset stomach

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What should I tell my care team before I take this medication?

They need to know if you have any of these conditions:

• Glaucoma
• High blood pressure
• Heart disease
• Liver disease
• Lung or breathing disease, such as asthma
• Pain or difficulty passing urine
• Prostate disease
• Stomach ulcers, other stomach or intestine problems
• An unusual or allergic reaction to diphenhydramine, other medications, foods, dyes, or preservatives
• Pregnant or trying to get pregnant
• Breastfeeding

What may interact with this medication?

Do not take this medication with any of the following:

• MAOIs, such as Carbex, Eldepryl, Marplan, Nardil, and Parnate

This medication may also interact with the following:

• Alcohol
• Barbiturates, such as phenobarbital
• Certain medications for stomach problems, such as chlordiazepoxide, dicyclomine
• Medications for bladder spasm, such as oxybutynin, tolterodine
• Medications for blood pressure
• Medications for mental health conditions
• Medications for movement abnormalities or Parkinson disease
• Medications for sleep
• Other medications for cold, cough, or allergy

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medication?

Your condition will be monitored carefully while you are receiving this medication. Tell your care team if your symptoms do not start to get better or if they get worse.

Your mouth may get dry. Chewing sugarless gum or sucking hard candy and drinking plenty of water may help. Contact your care team if the problem does not go away or is severe.

This medication may affect your coordination, reaction time, or judgment. Do not drive or operate machinery until you know how this medication affects you. Sit up or stand slowly to reduce the risk of dizzy or fainting spells. Drinking alcohol with this medication can increase the risk of these side effects.