Drug Class Antihistamines

hydroxyzine (Vistaril, others) Antihistamine 1st Generation

IINDICATIONS- anxiety, Preoperative sedation, Antiemetic, Antipruritic, May be combined with opioid analgesics ACTION-Acts as a CNS depressant at the subcortical level of the CNS, Has anticholinergic, antihistaminic, and antiemetic properties, Blocks histamine 1 receptors THERAPEUTIC EFFECTS-Sedation, Relief of anxiety, Decreased nausea and vomiting, Decreased allergic symptoms associated with release of histamine, including pruritus CONTRINDICATED/PRECAUTIONS • Hypersensitivity• OB: Potential for congenital defects (oral clefts and hypoplasia of cerebral hemisphere• Lactation: Safety not established Use Cautiously in: • Severe hepatic dysfunction• OB: Has been used safely during labor • Pedi: Injection contains benzyl alcohol, which can cause potentially fatal gasping syndrome in neonates • Geri: Appears on Beers list. Geriatric patients are more susceptible to adverse reactions due to anticholinergic effects; dosage reduction recommended SIDE EFFECTS CNS: ataxia, Resp: wheezing. GU: urinary retention. Misc: chest tightness. DRUG DRUG • Additive CNS depression with other CNS depressants , including alcohol , antidepressants , antihistamines , opioid analgesics , and sedative/hypnotics • Additive anticholinergic effects with other drugs possessing anticholinergic properties , including antihistamines , antidepressants , atropine , haloperidol , phenothiazines , quinidine , and disopyramide • Can antagonize the vasopressor effects of epinephrine

promethazine (Phenergan) Antihistamine 1st generation

INDICATIONS Treatment of various allergic conditions and motion sickness• Preoperative sedation• Treatment and prevention of nausea and vomiting• Adjunct to anesthesia and analgesia ACTION-Blocks the effects of histamine• Has inhibitory effect on the chemoreceptor trigger zone in the medulla, resulting in antiemetic properties• Alters the effects of dopamine in the CNS• Possesses significant anticholinergic activity • Produces CNS depression by indirectly decreased stimulation of the CNS reticular system Therapeutic Effect(s):• Relief of symptoms of histamine excess usually seen in allergic conditions• Diminished nausea or vomiting • Sedation CONTRINDICATED/PRECAUTIONS• Hypersensitivity • Comatose patients• Prostatic hypertrophy• Bladder neck obstruction• Some products contain alcohol or bisulfites and should be avoided in patients with known intolerance• Angle-closure glaucoma • Pedi: May cause fatal respiratory depression in children <2 yr CAUTIONS• IV administration may cause severe injury to tissuePedi: For children >2 yr, use lowest effective dose, avoid concurrent respiratory depressants • OB: Has been used safely during labor; avoid chronic use during pregnancy • Lactation: Safety not established; may cause drowsiness in infant;Geri: Appears on Beers list. Sensitive to anticholinergic effects and have ↑ risk for side effects SIDE EFFECTSCNS: NEUROLEPTIC MALIGNANT SYNDROME, confusion, disorientation, sedation, dizziness, extrapyramidal reactions, fatigue, insomnia, nervousness.

Dexchlorpheniramine (Generic)

INDICATIONS used to treat sneezing; runny nose; itching, watery eyes; hives; rashes; itching; and other symptoms of allergies and the common cold. Action-1st Generation SIDE EFFECTSglaucoma or increased pressure in the eye; a stomach ulcer; an enlarged prostate, bladder problems, or difficulty urinating;an overactive thyroid (hyperthyroidism); hypertension or any type of heart problems; or asthma.

1st Generation Antihistamines (P) diphenhydramine (Benadryl, others) hydroxyzine (Vistaril, others) meclizine (Antivert) chlorpheniramine (Aller-Chlor, others) promethazine (Phenergan) dexchlorpheniramine (generic)

INDICATIONS- Relief of allergic symptoms caused by histamine ACTION- Antagonizes the effects of histamine at H1 receptor cites. Significant CNS depressant & anticholinergic properties CONTRAINDICATED IN- Acute attacks of asthma SIDE EFFECTS- paradoxical excitation (increased in children) tinnitus DRUG-DRUG Increased anticholinergic effects with tricyclic antidepressants, quinidine, or disopyramide. MAO inhibitors intensify and prolong the anticholinergic effects of antihistamines.

meclizine (Antivert, others) Antihistamine 1st generation

INDICATIONS-Relief of nausea and vomiting associated with motion sickness (Vertigo) ACTION• Has central anticholinergic, CNS depressant, and antihistaminic properties• Decreases excitability of the middle ear labyrinth and depresses conduction in middle ear vestibular-cerebellar pathway CONTRINDICATED/PRECAUTIONS• Hypersensitivity • OB: Has caused congenital malformations (cleft palate) in animal studies Use Cautiously in: • Prostatic hyperplasia • Angle-closure glaucoma • Lactation: Occasional use may be acceptable; prolonged use may expose infant to drug effects or may interfere with milk supply • Pedi: Children <12 yr (safety not established) • Geri: ↑ sensitivity and risk of adverse reactions ADVERSE EFFECTS- Dry mouth, blurry vision DRUG-DRUG- Additive anticholinergic effects with other drugs possessing anticholinergic properties , including some antihistamines , antidepressants , atropine , haloperidol , phenothiazines , quinidine , and disopyramide

Chlorpheniramine (Aller-Chlor, others) Antihistamine 1st generation

INDICATIONS• Relief of allergic symptoms caused by histamine release, including » Nasal allergies » Allergic dermatoses • Management of severe allergic or hypersensitivity reactions, including anaphylaxis and transfusion reactions ACTION-Antagonizes the effects of histamine at H2-receptor sites; does not bind to or inactivate histamine CONTRINDICATED/PRECAUTIONS• Hypersensitivity • Acute attacks of asthma • Lactation: Avoid use or use alternative feeding method • Known alcohol intolerance (some liquid forms) • Pedi: Children <4 yr (OTC cough and cold products containing this medication should be avoided) Use Cautiously in:• Angle-closure glaucoma • Liver disease • Geri: Appears on Beers list. Geriatric patients are more susceptible to adverse reactions due to anticholinergic effects • OB: Safety not established SIDE EFFECTS-EENT: blurred vision. CV: hypertension, arrhythmias, hypotension, palpitations.GI: dry mouth, constipation, obstruction. GU: retention, urinary hesitancy. DRUG-DRUG-• MAO inhibitors intensify and prolong anticholinergic effects of antihistamines • ↑ anticholinergic effects with other drugs possessing anticholinergic properties , including antidepressants , atropine , haloperidol , phenothiazines , quinidine , and disopyramide

diphenhydramine (benadryl, others) Antihistamine 1st Generation

Indications- Relief of allergic symptoms caused by histamine, anaphylaxis seasonal and perennial allergic rhinitis, allergic dermatoses, parkinson's disease, mild nighttime sedation, motion sickness, antitussive (syrup only) Action- Antagonizes the effects of histamine at H1 receptor cites. Significant CNS depressant & anticholinergic properties Contraindicated in- Acute attacks of asthma Side Effects- paradoxical excitation (increased in children) tinnitus Drug-Drug interactions- Increased anticholinergic effects with tricyclic antidepressants, quinidine, or disopyramide. MAO inhibitors intensify and prolong the anticholinergic effects of antihistamines.