I.                    Histamine acts on smooth muscle of vascular system ro dilate arterioles and increase permeability of capillaries and venules, producing swelling and redness, inflammatory response to allergy and tissue injury.  There are three types of histamine receptors

                                                               i.      Type 1 (H₁) contract smotth muscle to dilate capillaries

                                                             ii.      Type 2 increase heart rate and gastric secretions

                                                            iii.      Type 3 are throughout the nervous system

                                                               i.      First generation – greater penetration of blood brain barrier, causing sleepiness, etc; but can do other things like treat nausea and itching

1.      brompheniramine

2.      chlorpheniramine

3.      clemastine

4.      dephenhydramine

5.      promethazine

                                                             ii.      Second generation – lessCNS penetration and not really sedating

1.      aselastine

2.      cetirizine (Zyrtec)

3.      desloratadine (Clainex)

4.      fexofenadine (Allegra)

5.      levocetirizine

6.      loratadine (Claritin, Alavert)

a.       – block Type 1 (H₁) histamine receptors.  Are H1 antagonists.  There are H2 receptors also (and maybe others) but antihistamines act of Type 1.

                                                               i.      First generation – non-selective binding of peripheral andCNS receptors, while

                                                             ii.      2^nd generation are selective for peripheral H1 receptors, less sedating.

1.  Allergies
2. mild angioedema (an allergic rxn)
3. adjunct therapy to anaphylactic shock 
4. treatment of parkinsonism
5. relief of motion sickness
6. relief of N/V
7. relief of vasomotor rhinitis
8. sedation

                                                               i.      CNS – First generation cause drowsiness and disturbed coordination

                                                             ii.      Repiratory – dryness of mouthm, nose, and throat; thickening of bronchial secretions.  These are caused by their ANTICHOLINERGIC ACTIONS and are more prominent with the 1^st generation antihistamines.
ANTICHOLINERGIC EFFECTS are dry mouth, nose and throat, thickening of bronchial secretions, confusion, constipation, urinary retention, delirium

                                                               i.      Hypersensitivity

                                                             ii.      Do not give to children under 2 can cause fatal respiratory depression

                                                            iii.      Pregnancy

1.      First generation – don’t give during pregnancy, category C

2.      Second generation – cat B

                                                           iv.      Known hypersensitivities (yes people can be allergic to antiallergy meds)

                                                             v.      1^st generation contraindicated in pregnant, nursing, newborns.  Also in those taking MAOIs; pts with glaucoma, stenosing peptic ulcer, prostate hypertrophy, bladder neck obstruction.

                                                           vi.      Second generation

1.      Certirizine is contraindicated with hydroxyzine

1. those with bronchial asthma
2. CV disease
3. certain glaucoma
4. hypertension
5. ulcer
6. urinary retention
7. hyperthyroidism
8. impaired kidney function

                                                               i.      Refampin for TB – will reduce antihist absorp

                                                             ii.      MAOIs – will increase anticholinergic and sedative effects of antihistamine

                                                            iii.      CNS depressants like alcohol and opioids have additive effect (moreCNS depression)

                                                           iv.      Beta blockers increase risk for CV effects especially benedryl

                                                             v.      Antacids (mag/alum) decrease concentration of antihistamines in blood

1.      Preadmin – What are symptoms; what other scrips.OTC/herbals; look at areas like eyes, nose, throat

a.       If promethazine (Phenegren) is used with an opioids to enhance the effects and reduce the doage of the opioids, the nurse should take the patients BP, pulse and resp before admin

2.      Postadmin – look for therapeutic response and adverse reactions and report; if given for severe allergic reactions (blood transfusion or drug allergy) assess pt frequently

1.      Optimal reponse – give with food to prevent GI, do not give within 2 hours of antacids.  Inform pt that adv rxns will decrease with continues use

2.      Adv rxn support

a.       Imparied Oral Mucus Membranes – take frequent sips of water.  Sugarless gum/hard candy also helpful. 

b.      Risk for Injury – esp. older adults more succeptible to antocholinergic effects.  Also have other conditions making more succeptible to falls.  Provide help with ambulation.  Give call light and instruct to call for help to get out of bed.  If taken at home, instruct to refrain from driving or other activities that require clear mind.  

1.      Review drug regimen and adv rxns.  Explain therapeutic benefit

2.      Do not drive or perform other haz tasks if drowsi

3.      Avoid alcohol or other meds than cause sleepiness

4.      take with food to prevent GI upset.  Loratadine should be taken on empty however.

5.      Do not take within 2 hours of antacids (fexofenadine only). 

6.      Take frequent sips water or gum/hard candy for dry mouth.

7.      Don’t crush/chew sustained relief

                                                               i.      Ephedrine

                                                             ii.      Epinephrine (adrenalin)

                                                            iii.      Naphazoline

                                                           iv.      Oxymetazoline (Afrin)

                                                             v.      Phenylephrine

                                                           vi.      Pseudoephedrine

                                                          vii.      Tetrahydrozoline

                                                        viii.      xylometazoline

decongestants

reduce swelling of nasal passeages to enhance sinus drainage

a.       are sympathomimetic b/c produce local vasoconstriction of small vessels in nasal membranes.  Reduces swelling.  Can be topical like afrin or oral

                                                               i.      pseudoephidrine and tetrahydrozoline cause anxiety, restlessness, arrythmias, N/V and blurred vision

                                                             ii.      the rest can cause nasal burning, dryness and rebound congestion

•  in pts with known hypersensitivities
• pts taking MAOIs. 
• Sustained release pseudoeph. not for children under 12.

                                                               i.      Thyroid disease

                                                             ii.      Diabetics (WHY?)

                                                            iii.      CV disease

                                                           iv.      Prostate hypertrophy

                                                             v.      Hypertension

                                                           vi.      Glaucoma

                                                          vii.      Preg cat C (not safe)

                                                               i.      MAOIs can cause severe headache, hypertension (HT) possible severe crisis hypertensive

                                                             ii.      Beta blockers – can cause hypertension followed by bradycardia

1.      Preadmin – assess symptoms and vitals (b/c these drugs affect BP and heart)  Assess lung sounds.  Obtain hx of use of these products.

2.      Postadmin – reassess vitals and level of congestions.  Has drug been effective?  Any adverse reactions?

1.      Promotion of optimal response – don’t use decongestants if contraindicated or in precautionary group (HT, thyroid disease, etc)
Pts older than 60 at greater risk for adv rxns including hallucinations, convulsions andCNS depression

2.      Monitoring/managing pt needs re: adv rxns

a.       Ineffective airway clearance – overuse of drug will cause rebound effect.  Teach pt to take as prescribed.  If rebound occurs, stop using and try saline irrigation.

1.      UAD

2.      Explain rebound

3.      Describe adv rxns

4.      Do not share nasal sprays

5.      Explain how to admin nasal spray or drops

6.      If no improvement in 7 days or accompanied by high fever, consultPCP