Rochelle asked
I was wondering what exactly Xanax is. Is it an allergy antihistamine?
Answer
Xanax (alprazolam) is not classified as an antihistamine. Antihistamines and benzodiazepines share little in common and are used to treat different conditions.
Benzodiazepine and antihistamine drug classes are detailed below.
Benzodiazepines
As stated, Xanax (alprazolam) is a benzodiazepine, not an antihistamine.
Key points of benzodiazepines include:
- As a class of drugs, benzodiazepines are among the most commonly prescribed and are used for a wide variety of indications, including insomnia, anxiety disorders, seizure disorders, and alcohol withdrawal.
- Within the benzodiazepine class, the individual drugs are primarily differentiated by their pharmacokinetic profiles. Differences among them include:
- Half-life (long-acting, medium-acting, and short-acting)
- Onset of action (rapid, intermediate, or slow)
- Metabolic pathways (which influences potential drug and disease interactions)
Extended use of benzodiazepine drugs have the risk of causing physiologic dependence. Physiologic dependence is often associated with withdrawal symptoms if a medication is discontinued abruptly, without dose titration.
List Of Benzodiazepines
| Benzodiazepine | Onset Of Action |
|---|---|
| Xanax (Alprazolam) | Rapid |
| Librium (Chlordiazepoxide) | Intermediate |
| Onfi (Clobazam) | Slow |
| Klonopin (Clonazepam) | Rapid |
| Tranxene (Clorazepate) | Intermediate |
| Valium (Diazepam) | Rapid |
| Prosom (Estazolam) | Intermediate |
| Dalmane (Flurazepam) | Rapid |
| Ativan (Lorazepam) | Rapid |
| Versed (Midazolam) | Rapid |
| Serax (Oxazepam) | Slow |
| Doral (Quazepam) | Intermediate |
| Restoril (Temazepam) | Intermediate |
| Halcion (Triazolam) | Rapid |
Xanax Information
Xanax (alprazolam) is a rapid-acting oral benzodiazepine, used for the treatment of anxiety and panic disorders. It is also used off-label for the short-term treatment of insomnia.
Xanax has a short half-life but has a relatively high potential for abuse due to its quick-acting effects. Discontinuation can sometimes be difficult as there is a high risk of withdrawal symptoms in-between doses and it may need to be tapered over weeks to months.
The onset of action of Xanax is around 15 to 30 minutes after taking by mouth, with peak concentrations occurring within 1—2 hours. Xanax is also available as an extended-release dosage form, Xanax XR.
Antihistamines
Antihistamines are the most common treatment for allergy symptoms, which includes:
- Sneezing
- Nasal congestion
- Runny nose
- Itchy and watery eyes
- Urticaria (e.g. hives)
Antihistamines do not block the release of histamine, but rather block the receptors that histamine (which causes allergy symptoms) bind to that are located all over the body.
Histamine plays a central role in the allergic response. When histamine is released, it has a wide range of effects including:
- Vasodilation (dilation of the blood vessels)
- Cardiac effects
- Contraction of Smooth Muscle
- Itching
Antihistamines are often divided into 'generations'.
First-Generation Antihistamines
First-generation antihistamines are more likely to cause sedation and have a shorter duration of action than second-generation antihistamines. First-generation antihistamines include:
- Benadryl (diphenhydramine)
- Tavist (clemastine)
- Chlor-Trimeton (chlorpheniramine)
- Dimenhydrinate
Due to their sedative properties, first-generation antihistamines are often used as night-time sleep aids. They can also be effective in attenuating allergic reactions.
Second-Generation Antihistamines
Second-generation antihistamines are less sedating than first-generation antihistamines and have a longer duration of action. Second-generation antihistamines include:
- Zyrtec (Cetirizine)
- Claritin (Loratadine)
- Allegra (Fexofenadine)
- Xyzal (Levocetirizine)
The second-generation antihistamines offer the convenience of once-daily dosing with little to no sedation.
Allegra (fexofenadine) and Claritin (loratadine) are completely non-drowsy (for most individuals) while Zyrtec (cetirizine) and Xyzal (levocetirizine) are not classified as non-drowsy. All second-generation antihistamines have a long duration of action and can generally be dosed once every 24 hours.
Antihistamines do not have a risk of withdrawal, unlike benzodiazepines (as discussed above).
Summary
- Xanax (alprazolam) is not classified as an antihistamine. It is a benzodiazepine.
- Benzodiazepines and antihistamines are two distinct classes of medications and vary in their indication, mechanism of action, side effects, etc...
