Pharmacy Clinic
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Common Cold
Treatment
Antihistamines
First-generation antihistamines such as diphenhydramine, chlorpheniramine, clemastine, hydroxyzine or triprolidine
do cause marked sedation, central nervous system (CNS) dysfunction and anticholinergic adverse effects, resulting
in performance or cognitive function impairment and therapy non-adherence.
The second-generation antihistamines, included astemizole, terfenadine, loratadine, cetirizine, and fexofenadine,
have been known as the "nonsedating antihistamines," were developed in the 1980s to minimize these side effects.
Terfenadine and astemizole were removed from the market due to serious cardiovascular events related to torsade
de pointes.
The newest antihistamine agent, desloratadine, an active metabolite of loratadine has been categorized under the
third-generation antihistamines and is currently the only agent in this class.
These agents have been used clinically to treat various allergic disorders such as seasonal or perennial allergic
rhinitis and chronic urticaria.
The "nonsedating antihistamines," specifically loratadine and fexofenadine have been identified as the most
commonly prescribed drugs in the treatment of allergic rhinitis in a managed care population.
Background
Histamine was first identified in 1910 and recognized in the 1920s as a major pathogenic mediator of allergic
disorders. Histamine receptor antagonist was introduced in 1937, and from 1942 to 1981, more than 40
compounds have reached the market.
Antihistamines have been categorized over the years as first, second or third-generation classes. Although very
effective,
This is a classic 12 lead EKG of a patient with Torsade de Pointes.
It shows
• the polymorphic nature of the tachycardia,
• the long QT interval and
• the initiation of the tachycardia with a late coupled P.V.C.
Torsade is a polymorphic tachycaridia that is associated with prolongation of the QT interval (usually greater than
600 ms) and can be acquired or congenital. This arrhythmia was responsible for Quinidine syncope and is an
important cause of sudden death in patients treated with type I and type III antiarrhythmic medications. The
electrical mechanism may be related to dispersion of repolarization or to triggered activity associated with after
depolarizations.
Besides medications, acquired Torsade can be associated with hypokalemia, and a slow heart rate (complete heart
block). This patient was a renal patient on dialysis who was admitted to hospital for an E.N.T. operation on one of
her sinuses. The arrhythmia was noted during the operation. At the time of the procedure she was taking sotalol
and this combined with her renal failure was the presumed cause of the arrhythmia.
Sotalol has both class II (beta-blocking) and class III (prolonging of action potential) effects. Sotalol is excreted
mainly by the kidneys and the dosing intervals should be lengthened when the creatinine clearance is less than 60
ml/min. As with the anti-arrhythmic effect of sotalol, Torsade de pointes is dose dependent and occurs in 0.5
percent of patients who taking 160 mg/day, 1.6 % taking 320 mg/day, and up to 5.8% taking more than 320
mg/day.
Pharmacology
Antihistamines are reversible competitive antagonists of histamine at H1 receptor sites. They do not prevent
histamine release or bind to the histamine that has already been released. The H1 receptor blockade results in
decreased vascular permeability, reduction of pruritus and relaxation of smooth muscle in the respiratory and
gastrointestinal tracts.
They are clinically efficacious for alleviating symptoms of allergic rhinitis that are attributed to the early-phase
reaction, such as rhinorrhea, pruritus, and sneezing. However, they are less efficacious in controlling nasal
congestion, which is related to the late-phase reaction.
Second or third generation antihistamines have entered the market that demonstrated improved peripheral H1
receptor selectivity, decreased lipophilicity in order to minimize CNS side effects and additional antiallergic properties
apart from histamine antagonism.
They interfere with mediator release from mast cells either by inhibiting calcium ion influx across mast cell/basophil
plasma membrane or by inhibiting intracellular calcium ion release within the cells. They may also inhibit the late-
phase allergic reaction by acting on leukotrienes or prostaglandins, or by producing an anti-platelet activating factor
effect
Indications
First-generation antihistamines are approved for:
Hypersensitivity reactions, type 1 that includes perennial or seasonal allergic rhinitis, vasomotor rhinitis, allergic
conjunctivitis, urticaria.
These agents can also be used as adjunctive anaphylactic therapy.
Diphenhydramine, hydroxyzine, and promethazine, have other indications in addition to the use in allergic reactions.
Diphenhydramine is used as anti-tussive, sleep aid, anti-parkinsonism or for motion sickness.
Hydroxyzine can be used as pre-medication or following general anesthesia sedative, adjunctive analgesic in
preoperative or prepartum, and anti-emetic agent.
Promethazine is used for motion sickness, pre- and postoperative or obstetric sedation, or adjunctive analgesia for
postoperative pain.
Contraindications/Precautions
First-generation antihistamines:
1. Hypersensitivity to specific or structurally related antihistamines;
2. Newborn or premature infants;
3. Nursing mothers;
4. Narrow-angle glaucoma;
5. Stenosing peptic ulcer;
6. Symptomatic prostatic hypertrophy;
7. Bladder neck obstruction;
8. Pyloroduodenal obstruction;
9. Lower respiratory tract symptoms (including asthma);
10. Monoamine oxidase inhibitor (MAOI) use;
11. Elderly,
12. Debilitated patients (cyproheptadine).
Second- and third-generation antihistamines:
1. Hypersensitivity to specific or structurally related antihistamines.
2. Desloratadine is contraindicated in those with loratadine hypersensitivity,
3. cetirizine is contraindicated in those with a known hypersensitivity to hydroxyzine.
Adverse effects
First-generation antihistamines:
1. Allergic - photosensitivity, anaphylactic shock, drug rash, dermatitis
2. Cardiovascular - postural hypotension, palpitations, reflex tachycardia, venous thrombosis at injection site
(IV promethazine)
3. Central nervous system (CNS) - drowsiness, sedation, dizziness, disturbed coordination, fatigue,
confusion, extrapyramidal reactions may occur with high doses
4. Gastrointestinal - epigastric distress, anorexia, bitter taste (nasal spray)
5. Genitourinary - urinary frequency, dysuria, urinary retention
6. Respiratory - chest tightness, wheezing, dry mouth, nose and throat, thickening of bronchial secretions,
epistaxis and nasal burning (nasal spray)
Second- and third-generation antihistamines:
1. Allergic - photosensitivity, anaphylactic shock, drug rash, dermatitis
2. Central nervous system* - somnolence/ drowsiness, headache, fatigue, sedation
3. Respiratory** - dry mouth, nose and throat (cetirizine, loratadine)
4. Gastrointestinal** - nausea, vomiting, abdominal distress (cetirizine, fexofenadine)
*CNS side effects are comparable to placebo in clinical studies with the exception of cetirizine that has shown
significantly more sedation, somnolence and drowsiness than placebo, and may be similar to the first-generation
antihistamines
**Respiratory and gastrointestinal side effects are less frequent than the first-generation antihistamines.
Vitamin C for preventing and treating the common cold
Antihistamines
First-generation antihistamines such as diphenhydramine, chlorpheniramine, clemastine, hydroxyzine or triprolidine
do cause marked sedation, central nervous system (CNS) dysfunction and anticholinergic adverse effects, resulting
in performance or cognitive function impairment and therapy non-adherence.
The second-generation antihistamines, included astemizole, terfenadine, loratadine, cetirizine, and fexofenadine,
have been known as the "nonsedating antihistamines," were developed in the 1980s to minimize these side effects.
Terfenadine and astemizole were removed from the market due to serious cardiovascular events related to torsade
de pointes.
The newest antihistamine agent, desloratadine, an active metabolite of loratadine has been categorized under the
third-generation antihistamines and is currently the only agent in this class.
These agents have been used clinically to treat various allergic disorders such as seasonal or perennial allergic
rhinitis and chronic urticaria.
The "nonsedating antihistamines," specifically loratadine and fexofenadine have been identified as the most
commonly prescribed drugs in the treatment of allergic rhinitis in a managed care population.
Background
Histamine was first identified in 1910 and recognized in the 1920s as a major pathogenic mediator of allergic
disorders. Histamine receptor antagonist was introduced in 1937, and from 1942 to 1981, more than 40
compounds have reached the market.
Antihistamines have been categorized over the years as first, second or third-generation classes. Although very
effective,
This is a classic 12 lead EKG of a patient with Torsade de Pointes.
It shows
• the polymorphic nature of the tachycardia,
• the long QT interval and
• the initiation of the tachycardia with a late coupled P.V.C.
Torsade is a polymorphic tachycaridia that is associated with prolongation of the QT interval (usually greater than
600 ms) and can be acquired or congenital. This arrhythmia was responsible for Quinidine syncope and is an
important cause of sudden death in patients treated with type I and type III antiarrhythmic medications. The
electrical mechanism may be related to dispersion of repolarization or to triggered activity associated with after
depolarizations.
Besides medications, acquired Torsade can be associated with hypokalemia, and a slow heart rate (complete heart
block). This patient was a renal patient on dialysis who was admitted to hospital for an E.N.T. operation on one of
her sinuses. The arrhythmia was noted during the operation. At the time of the procedure she was taking sotalol
and this combined with her renal failure was the presumed cause of the arrhythmia.
Sotalol has both class II (beta-blocking) and class III (prolonging of action potential) effects. Sotalol is excreted
mainly by the kidneys and the dosing intervals should be lengthened when the creatinine clearance is less than 60
ml/min. As with the anti-arrhythmic effect of sotalol, Torsade de pointes is dose dependent and occurs in 0.5
percent of patients who taking 160 mg/day, 1.6 % taking 320 mg/day, and up to 5.8% taking more than 320
mg/day.
Pharmacology
Antihistamines are reversible competitive antagonists of histamine at H1 receptor sites. They do not prevent
histamine release or bind to the histamine that has already been released. The H1 receptor blockade results in
decreased vascular permeability, reduction of pruritus and relaxation of smooth muscle in the respiratory and
gastrointestinal tracts.
They are clinically efficacious for alleviating symptoms of allergic rhinitis that are attributed to the early-phase
reaction, such as rhinorrhea, pruritus, and sneezing. However, they are less efficacious in controlling nasal
congestion, which is related to the late-phase reaction.
Second or third generation antihistamines have entered the market that demonstrated improved peripheral H1
receptor selectivity, decreased lipophilicity in order to minimize CNS side effects and additional antiallergic properties
apart from histamine antagonism.
They interfere with mediator release from mast cells either by inhibiting calcium ion influx across mast cell/basophil
plasma membrane or by inhibiting intracellular calcium ion release within the cells. They may also inhibit the late-
phase allergic reaction by acting on leukotrienes or prostaglandins, or by producing an anti-platelet activating factor
effect
Indications
First-generation antihistamines are approved for:
Hypersensitivity reactions, type 1 that includes perennial or seasonal allergic rhinitis, vasomotor rhinitis, allergic
conjunctivitis, urticaria.
These agents can also be used as adjunctive anaphylactic therapy.
Diphenhydramine, hydroxyzine, and promethazine, have other indications in addition to the use in allergic reactions.
Diphenhydramine is used as anti-tussive, sleep aid, anti-parkinsonism or for motion sickness.
Hydroxyzine can be used as pre-medication or following general anesthesia sedative, adjunctive analgesic in
preoperative or prepartum, and anti-emetic agent.
Promethazine is used for motion sickness, pre- and postoperative or obstetric sedation, or adjunctive analgesia for
postoperative pain.
Contraindications/Precautions
First-generation antihistamines:
1. Hypersensitivity to specific or structurally related antihistamines;
2. Newborn or premature infants;
3. Nursing mothers;
4. Narrow-angle glaucoma;
5. Stenosing peptic ulcer;
6. Symptomatic prostatic hypertrophy;
7. Bladder neck obstruction;
8. Pyloroduodenal obstruction;
9. Lower respiratory tract symptoms (including asthma);
10. Monoamine oxidase inhibitor (MAOI) use;
11. Elderly,
12. Debilitated patients (cyproheptadine).
Second- and third-generation antihistamines:
1. Hypersensitivity to specific or structurally related antihistamines.
2. Desloratadine is contraindicated in those with loratadine hypersensitivity,
3. cetirizine is contraindicated in those with a known hypersensitivity to hydroxyzine.
Adverse effects
First-generation antihistamines:
1. Allergic - photosensitivity, anaphylactic shock, drug rash, dermatitis
2. Cardiovascular - postural hypotension, palpitations, reflex tachycardia, venous thrombosis at injection site
(IV promethazine)
3. Central nervous system (CNS) - drowsiness, sedation, dizziness, disturbed coordination, fatigue,
confusion, extrapyramidal reactions may occur with high doses
4. Gastrointestinal - epigastric distress, anorexia, bitter taste (nasal spray)
5. Genitourinary - urinary frequency, dysuria, urinary retention
6. Respiratory - chest tightness, wheezing, dry mouth, nose and throat, thickening of bronchial secretions,
epistaxis and nasal burning (nasal spray)
Second- and third-generation antihistamines:
1. Allergic - photosensitivity, anaphylactic shock, drug rash, dermatitis
2. Central nervous system* - somnolence/ drowsiness, headache, fatigue, sedation
3. Respiratory** - dry mouth, nose and throat (cetirizine, loratadine)
4. Gastrointestinal** - nausea, vomiting, abdominal distress (cetirizine, fexofenadine)
*CNS side effects are comparable to placebo in clinical studies with the exception of cetirizine that has shown
significantly more sedation, somnolence and drowsiness than placebo, and may be similar to the first-generation
antihistamines
**Respiratory and gastrointestinal side effects are less frequent than the first-generation antihistamines.
Vitamin C for preventing and treating the common cold
Acne Vulgaris
Hemorrhoid
Constipation
Cough
Drug Interactions
Kidney Problems
Nausea
Diarrhea
Heart Burn
Obstetrics
Arthritis
UTI
Common Cold
GERD
URTIs
LRTIs
Asthma
Labor
PinWorm
Hypercholesterolemia
Fungal Infections
Cardiovascular
diseases
Diabetes Mellitus
Hemorrhoid
Constipation
Cough
Drug Interactions
Kidney Problems
Nausea
Diarrhea
Heart Burn
Obstetrics
Arthritis
UTI
Common Cold
GERD
URTIs
LRTIs
Asthma
Labor
PinWorm
Hypercholesterolemia
Fungal Infections
Cardiovascular
diseases
Diabetes Mellitus
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| More detailed note on antihistamines (Winword document) |