Allergy Shots (Antihistamines) Side Effects, Safety & Types

What are antihistamine
shots,
and what are the medical uses for this type of drug?

Antihistamine shots are prescription medications that are used for the rapid
medical
treatment of conditions such as:

• Allergic reactions (a severe allergy to a substance)

• Anxiety

• Nausea

• Vomiting

• Motion sickness

• To induce sedation when injected into a patient

Antihistamine shots also are used to alleviate extra pyramidal symptoms
of antipsychotic medications.

Histamine is a chemical that causes many
signs and symptoms of allergy.
Histamine is released from histamine-storing cells (mast cells) and attaches to
other cells that have receptors for histamine on their surfaces. Histamine
stimulates the cells to release chemicals that produce effects that we associate
with allergy. Antihistamines blocks histamine receptors and thus prevent
activation of cells with histamine receptors by histamine.

What are examples of
generic and brand names of antihistamine injections available in the US?

Examples of the brand and generic names for this type of medication include:

• diphenhydramine (Benadryl)
• promethazine
  (Phenergan)
• hydroxyzine hydrochloride (Restall,
  Vistacot)
• dimenhydrinate (Dramamine, Driminate)

The formulation of this drug is available by prescription only to treat a
patient with a specific condition. It is not
available over-the-counter (OTC). Other formulations of antihistamine drugs
are available over-the-counter that treat medical conditions such as:

• Mild allergic reactions
• Itching

• Mild allergy symptoms

• Allergic rhinitis

• Runny nose

Examples of OTC medicine available over-the-counter include:

• diphenhydramine (Benadryl)
• certirizine (Zyrtec)
• loratadine (Claritin)
• fexofenadine (Allegra)
• desloratadine (Clarinex)
• loratadine ODT (Alavert,
  Tavist ND)

What are the side effects of antihistamine
shots?

The common side effects of this type of medication include:

• Dizziness

• Drowsiness (sleepiness)

• Dry mouth

• Blurred vision

• Urinary retention

• Increased or decreased
  blood pressure

• Headache

• Abnormal heart rate

• Nausea

• Trouble breathing
• Tiredness (fatigue)
• Weakness

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Which drugs interact with antihistamine
shots?

Antihistamine injections have additive effects if used with alcohol or other
central nervous system depressant medications such as:

• alprazolam (Xanax)
• clonazepam (Klonopin)
• diazepam (Valium)
• zolpidem (Ambien)
• zaleplon (Sonata)
• phenobarbital
• butalbital/acetaminophen/caffeine (Fioricet)
• codeine
• morphine (MSIR)
• hydromorphone (Dilaudid)
• buprenorphine (Buprenex)
• azelastine (Astelin)

Effects of antihistamines are prolonged if combined with monoamine oxidase
inhibitors (MAOIs) such as:

• phenelzine (Nardil)
• selegiline (Zelapar, Emsam, and
  Eldepryl)
• tranylcypromine (Parnate)
• procarbazine (Matulane)
• rasagiline (Azilect)
• isocarboxazid (Marplan).

Antihistamine injections should be used with caution if the patient under
medical care and receiving treatment with an
MAOI drug.

Allergies can best be described as:
See Answer

What formulations of antihistamine
injections are available?

• Prescription antihistamine injections are available in injection form.
• Diphenhydramine, promethazine, and
  dimenhydrinate are administered intramuscularly and intravenously.
• Hydroxyzine hydrochloride is
  administered only intramuscularly.
• Antihistamine injections are not
  recommended for administration via subcutaneous route.

Is it safe to have antihistamine
shots during pregnancy or while breastfeeding?

• FDA lists diphenhydramine and dimenhydrinate as Pregnancy Category B and
  promethazine as Pregnancy Category C. Hydroxyzine does not have a Pregnancy
  Category. These categories mean that the safe and effective use of any
  antihistamine injection drug is not established in during pregnancy;
  therefore, if a patient is pregnant, medical treatment with this drug should be used only if clearly needed.
• It is not known whether an injected antihistamine drug enters breast milk;
  therefore, patients who are pregnant should seek medical advise and use caution before treatment with a prescription antihistamine injection
  medication in
  women who are breastfeeding.