NEET MDS Synopsis
Anti-Histamines
Pharmacology
Anti-Histamines:
The effect of histamine can be opposed in three ways:
1. Physiological antagonism: by using a drug to oppose the effect (e.g adrenaline). Histamine constricts bronchi,
causes vasodilatation which increases capillary permeability. Adrenaline opposes this effect by a mechanism unrelated to histamine.
2. By preventing histamine from reaching its site of action (receptors), By competition with H1-H2 receptors (Drug antagonisms).
3. By preventing the release of histamine. (adrenal steroids and sodium-cromoglycate can suppress the effect on the tissues)
Types of Anti-histamine drugs
Selected H1 antagonist drugs
First-generation H1 receptor antagonists:
Chlorpheniramine (Histadin) & Dexchlorpheniramine
Diphenhydramine (Allermine)
Promethazine (Phenergan) - strong CNS depressants
Cyproheptadine (Periactin)
ACTION
These drugs bind to both central and peripheral H1 receptors and can cause CNS depression or stimulation.
- They usually cause CNS depression (drowsiness,sedation) with usual therapeutic doses
- Cause CNS stimulation (anxiety, agitation)
with excessive doses, especially in children.
They also have Anticholinergic effects (e.g. dry mouth, urinary retention, constipation, blurred vision).
Second-generation H1 receptor antagonists (non-sedating) agents
Terfenadine
Fexofenadine
Loratadine
Acravistine and Cetirizine
Astemizol
Action
They cause less CNS epression because they are selective for peripheral H1 receptors and do not cross the blood brain barrier.
Indications for use
The drugs can relieve symptoms but don’t relieve hypersensitivity.
1) Allergic rhinitis. Some relief of sneezing, rhinorrhea, nasal airway obstruction and conjunctivitis are with the use of antihistamine.
2) Anaphylaxis. Antihistamine is helpful in treating urticaria and pruritus.
3) Allergic conjunctivitis. This condition, which is characterized by redness, itching and tearing of the eyes.
4) Drug allergies. Antihistamines may be given to prevent or treat reactions to drugs (e.g, before a dignostic test that
uses an iodine preparation).
5) Transfusions of blood and blood products.
6) Dermatologic conditions. Antihistamines are the drug of choice for treatment of allergic contact dermatitis and
acute Urticaria. Urticaria often occurs because the skin has many mast cells to release histamine.
7) Miscellaneous. Some antihistamines are commonly used for non-allergic disorder such as motion sickness, nausea, vomiting, sleep, cough or add to cough mixtures.
Contraindication
hypersensitivity to the drugs, narrow-angle glaucoma, prostatic hypertroph, stenosing peptic ulcer, bladder neck obstruction, during pregnancy and lactating women
Adverse effects:
Drowsiness and sedation
Anticholinergic
Some antihistamines may cause dizziness, fatigue, hypotention, headache, epigastric distress and photosensitivity
Serious adverse reaction including cardiac arrest & death, have been reported in patients receiving high dose astemizole
H2-receptor antagonists
Cimetidine (Tagamate), Ranitidine (Zantac), Fomatidine, Nizatidine.
Mechanism of action
Numerous factors influence acid secretion by the stomach, including food, physiological condition and drugs. H2 receptor blockers reduce basal acid-secretion by about 95% and food stimulated acid-secretion by about 70%. Both conc. and vol. of H ions will decrease.
Pharmacokinetics:
1) They are all well absorbed after oral dose.
2) Antacids decrease their absorption in about 10-20%
Uses
Cimetidine - reduction of gastric secretion is beneficial, these are in main duodenal ulcer, benign gastric ulcer, stomach ulcer and reflux eosophagitis.
Rantidine -used as alternative for duodenal ulcer
Adverse effects:
headache, dizziness, constipation, diarrhoea, tiredness and muscular pain.
Casting ring
Dental Materials
Casting ring
CASTING RING LINERS
Most common way to provide investment expansion is by using a liner in the casting ring .Traditionally asbestose was used .
Non asbestose ring liner used are :
1) Aluminosilicate ceramic liner .
2) Cellulose paper liner .
The aim of using a resilient liner is to
-. allow different types of investmentbexpansion (act as a cushion)
_. facilitate venting during casting procedure.
_. facilitate the removal of the investment block after casting.&. prevent the distortion by permitting the outward expansion of the mold.
The casting ring holds the investment in place during setting and restricts the expansion of the mold. Normally a resilient liner is placed inside the ring leaving about 2-3 mm from both ends to allow for supporting contact of the investment with the casting ring.
Purpose of Casting Ring Liner
Ringer liner is he most commonly used technique to provide investment expansion. To ensure uniform expansion , liner is cut to fit the inside diameter of the casting ring with no overlap.
Non-asbestos Ring Liners: Ceramic (aluminum silicate) Cellulose (paper) Ceramic-cellulose combination Safety of the ceramic ring liners remains uncertain, because aluminum silicate also appears capable of producing hazardous-size respirable particles
Dental stains
Pedodontics
Dental stains in children can be classified into two primary categories: extrinsic
stains and intrinsic
stains. Each type has distinct causes and characteristics.
Extrinsic Stains
Definition:
These stains occur on the outer surface of the teeth and are typically
caused by external factors.
Common Causes:
Food and Beverages: Consumption of dark-colored foods and
drinks, such as berries, soda, and tea, can lead to staining.
Bacterial Action: Certain bacteria, particularly chromogenic
bacteria, can produce pigments that stain the teeth.
Poor Oral Hygiene: Inadequate brushing and flossing can lead to
plaque buildup, which can harden into tartar and cause discoloration.
Examples:
Green Stain: Often seen in children, particularly on the
anterior teeth, caused by chromogenic bacteria and associated fungi. It
appears as a dark green to light yellowish-green deposit, primarily on
the labial surfaces.
Brown and Black Stains: These can result from dietary habits,
tobacco use, or iron supplements. They may appear as dark spots or lines
on the teeth.
Intrinsic Stains
Definition:
These stains originate from within the tooth structure and are often
more difficult to treat.
Common Causes:
Medications: Certain antibiotics, such as tetracycline, can
cause grayish-brown discoloration if taken during tooth development.
Fluorosis: Excessive fluoride exposure during enamel formation
can lead to white spots or brown streaks on the teeth.
Genetic Factors: Conditions affecting enamel development can
result in intrinsic staining.
Examples:
Yellow or Gray Stains: Often linked to genetic factors or
developmental issues, these stains can be more challenging to remove and
may require professional intervention.
Management and Prevention
Regular Dental Check-ups:
Schedule routine visits to the dentist for early detection and
management of stains.
Good Oral Hygiene Practices:
Encourage children to brush twice a day and floss daily to prevent
plaque buildup and staining.
Dietary Considerations:
Limit the intake of sugary and acidic foods and beverages that can
contribute to staining.
Actinic keratosis
General Pathology
Actinic keratosis
1. Dry, scaly plaques with an erythematous base.
2. Similar to actinic cheilosis, which occurs along the vermilion border of the lower lip.
3. Caused by sun damage to the skin.
4. Dysplastic lesion, may be premalignant.
Dyes for detection of carious enamel
Conservative Dentistry
Various dyes have been tried to detect carious enamel, each having some
Advantages and Disadvantages:
‘Procion’ dyes stain enamel lesions but the staining becomes
irreversible because the dye reacts with nitrogen and hydroxyl groups of enamel
and acts as a fixative.
‘Calcein’ dye makes a complex with calcium and remains bound
to the lesion.
‘Fluorescent dye’ like Zyglo ZL-22
has been used in vitro which is not suitable in vivo. The dye is made visible by
ultraviolet illumination.
‘Brilliant blue’ has also been used to enhance the
diagnostic quality of fiberoptic transillumination.
Other lung diseases
General Pathology
Other lung diseases
1.Sarcoidosis
1. Sarcoidosis
a. More common in African-Americans.
b. Associated with the presence of noncaseating granulomas.
Sarcoidosis is an immune system disorder characterised by non-necrotising granulomas (small inflammatory nodules). Virtually any organ can be affected, however, granulomas most often appear in the lungs or the lymph nodes.
Signs and symptoms
Sarcoidosis is a systemic disease that can affect any organ. Common symptoms are vague, such as fatigue unchanged by sleep, lack of energy, aches and pains, dry eyes, blurry vision, shortness of breath, a dry hacking cough or skin lesions. The cutaneous symptoms are protean, and range from rashes and noduli (small bumps) to erythema nodosum or lupus pernio
Renal, liver, heart or brain involvement may cause further symptoms and altered functioning. Manifestations in the eye include uveitis and retinal inflammation
Sarcoidosis affecting the brain or nerves is known as neurosarcoidosis.
Hypercalcemia (high calcium levels) and its symptoms may be the result of excessive vitamin D production
Sarcoidosis most often manifests as a restrictive disease of the lungs, causing a decrease in lung volume and decreased compliance (the ability to stretch). The vital capacity (full breath in, to full breath out) is decreased, and most of this air can be blown out in the first second. This means the FEV1/FVC ratio is increased from the normal of about 80%, to 90%.
Treatment
Corticosteroids, most commonly prednisone
2. Cystic fibrosis
a. Transmission: caused by a genetic mutation (nucleotide deletion) on chromosome 7, resulting in abnormal chloride channels.
b. The most common hereditary disease in Caucasians.
c. Genetic transmission: autosomal recessive.
d. Affects all exocrine glands. Organs affected include lungs, pancreas, salivary glands, and intestines. Thick secretions or mucous plugs are
seen to obstruct the pulmonary airways and intestinal tracts.
e. Is ultimately fatal.
f. Diagnostic test: sweat test—sweat contains increased amounts of chloride.
3. Atelectasis
a. Characterized by collapse of the alveoli.
b. May be caused by a deficiency of surfactant and/or hypoventilation of alveoli.
Theories Regarding the Mineralization of Dental Calculus
PeriodontologyTheories Regarding the Mineralization of Dental Calculus
Dental calculus, or tartar, is a hard deposit that forms on teeth due to the
mineralization of dental plaque. Understanding the mechanisms by which plaque
becomes mineralized is essential for dental professionals in managing
periodontal health. The theories regarding the mineralization of calculus can be
categorized into two main mechanisms: mineral precipitation and the role of
seeding agents.
1. Mineral Precipitation
Mineral precipitation involves the local rise in the saturation of calcium
and phosphate ions, leading to the formation of calcium phosphate salts. This
process can occur through several mechanisms:
A. Rise in pH
Mechanism: An increase in the pH of saliva can lead to
the precipitation of calcium phosphate salts by lowering the precipitation
constant.
Causes:
Loss of Carbon Dioxide: Bacterial activity in
dental plaque can lead to the loss of CO2, resulting in an increase in
pH.
Formation of Ammonia: The degradation of proteins
by plaque bacteria can produce ammonia, further elevating the pH.
B. Colloidal Proteins
Mechanism: Colloidal proteins in saliva bind calcium
and phosphate ions, maintaining a supersaturated solution with respect to
calcium phosphate salts.
Process:
When saliva stagnates, these colloids can settle out, disrupting the
supersaturated state and leading to the precipitation of calcium
phosphate salts.
C. Enzymatic Activity
Phosphatase:
This enzyme, released from dental plaque, desquamated epithelial
cells, or bacteria, hydrolyzes organic phosphates in saliva, increasing
the concentration of free phosphate ions and promoting mineralization.
Esterase:
Present in cocci, filamentous organisms, leukocytes, macrophages,
and desquamated epithelial cells, esterase can hydrolyze fatty esters
into free fatty acids.
These fatty acids can form soaps with calcium and magnesium, which
are subsequently converted into less-soluble calcium phosphate salts,
facilitating calcification.
2. Seeding Agents and Heterogeneous Nucleation
The second theory posits that seeding agents induce small foci of
calcification that enlarge and coalesce to form a calcified mass. This concept
is often referred to as the epitactic concept or heterogeneous
nucleation.
A. Role of Seeding Agents
Unknown Agents: The specific seeding agents involved in
calculus formation are not fully understood, but it is believed that the
intercellular matrix of plaque plays a significant role.
Carbohydrate-Protein Complexes:
These complexes may initiate calcification by chelating calcium from
saliva and binding it to form nuclei that promote the deposition of
minerals.
Clinical Implications
Understanding Calculus Formation:
Knowledge of the mechanisms behind calculus mineralization can help
dental professionals develop effective strategies for preventing and
managing calculus formation.
Preventive Measures:
Maintaining good oral hygiene practices can help reduce plaque
accumulation and the conditions that favor mineralization, such as
stagnation of saliva and elevated pH.
Treatment Approaches:
Understanding the role of enzymes and proteins in calculus formation
may lead to the development of therapeutic agents that inhibit
mineralization or promote the dissolution of existing calculus.
Research Directions:
Further research into the specific seeding agents and the
biochemical processes involved in calculus formation may provide new
insights into preventing and treating periodontal disease.
Liver Diseases
General Pathology
1. Pyogenic liver abscesses may be caused by E. coli, Klebsiella, Streptococcus, Staphylococcus, Bacteroides, Pseudomonas, and fungi.
Parasitic infections
1. Schistosomiasis is caused by different organisms in different parts of the world.
a. Clinical features include splenomegaly, portal hypertension, and ascites. Lesions are caused by the immune response to ova.
2. Amebiasis is caused by Entamoeba histolytica.
a. Clinical features include bloody diarrhea, pain, fever, jaundice, and hepatomegaly.
Drug-induced liver damage may be caused by agents that are direct hepatotoxins, such as carbon tetrachloride, acetaminophen, methotrexate, anabolic steroids, and oral contraceptive pills.