NEET MDS Lessons
Pharmacology
First Generation Cephalosporins
Prototype Drugs are CEFAZOLIN (for IV use) and CEPHALEXIN (oral use).
1. Staph. aureus - excellent activity against b-lactamase-producing strains
Not effective against methicillin-resistant Staph. aureus & epidermidis
2. Streptococci - excellent activity versus Streptococcus sp.
Not effective against penicillin-resistant Strep. pneumoniae
3. Other Gm + bacteria - excellent activity except for Enterococcus sp.
4. Moderate activity against gram negative bacteria.
Caution: resistance may occur in all cases.
Susceptible organisms include:
E. coli
Proteus mirabilis
Indole + Proteus sp. (many strains resistant)
Haemophilus influenzae (some strains resistant)
Neisseria sp. (some gonococci resistant)
Uses
1. Upper respiratory tract infections due to Staph. and Strep.
2. Lower respiratory tract infections due to susceptible bacteria e.g. Strep.pneumoniae in penicillin-allergic patient (previous rash)
3. Uncomplicated urinary tract infections (Cephalexin)
4. Surgical prophylaxis for orthopedic and cardiovascular operations (cefazolin preferred because of longer half-life)
5. Staphylococcal infections of skin and skin structure
Ketoconazole
synthetic antifungal drug
used for infections such as athlete's foot, ringworm, candidiasis (yeast infection or thrush), jock itch.
Ketoconazole is used to treat eumycetoma, the fungal form of mycetoma.
MOA: Ketoconazole is imidazole structured, and interferes with the fungal synthesis of ergosterol, the main constituent of cell membranes, as well as certain enzymes. It is specific for fungi, as mammalian cell membranes contain no ergosterol.
Sensitive fungi Ketoconazole inhibits growth of dermatophytes and yeast species (such as Candida albicans).
Hydromorphone
- About 8-10 times more potent than morphine when given intravenously.
- Slightly shorter duration of action.
- More soluble than morphine, thus higher concentrations may be injected if necessary.
- Better oral/parenteral absorption ratio than morphine, but not as good as codeine or oxycodone.
- It is used for the treatment of moderate to severe pain
Biguanides
metformin
Mechanism
↓ gluconeogenesis
appears to inhibit complex 1 of respiratory chain
↑ insulin sensitivity
↑ glycolysis
↓ serum glucose levels
↓ postprandial glucose levels
Clinical use
first-line therapy in type II DM
Toxicity
no hypoglycemia
no weight gain
lactic acidosis is most serious side effect
contraindicated in renal failure
ANTIASTHMATIC AGENTS
Classification for antiasthmatic drugs.
I. Bronchodilators
i. Sympathomimetics (adrenergic receptor agonists)
Adrenaline, ephedrine, isoprenaline, orciprenaline, salbutamol, terbutaline, salmeterol, bambuterol
ii. Methylxanthines (theophylline and its derivatives)
Theophylline
Hydroxyethyl theophylline
Theophylline ethanolate of piperazine
iii. Anticholinergics
Atropine methonitrate
Ipratropium bromide
II. Mast cell stabilizer
Sodium cromoglycate
Ketotifen
III. Corticosteroids
Beclomethasone dipropionate
Beclomethasone (200 µg) with salbutamol
IV. Leukotriene pathway inhibitors
Montelukast
Zafirlukast
BradyKinin
An endogenous vasodilator occurring in blood vessel walls.
At least two distinct receptor types, B1 and B2, appear to exist for BradyKinin
Roles of bradykinin:
1) Mediator of inflammation and pain.
2) Regulation of microcirculation.
3) Their production is interrelated with clotting and fibrinolysin systems.
4) Responsible for circulatory change after birth.
5) Involved in shock and some immune reactions.
Phenobarbital (Luminal): for generalized tonic-clonic and partial seizures (not used for absence seizures)
Mechanism: enhances GABA inhibition (↑ open time of Cl channels in presence of GABA)
Side effects: sedation, ataxia, cognitive impairment, induction of hepatic microsomal enzymes