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Pharmacology

Chloramphenicol

derived from the bacterium Streptomyces venezuelae

Chloramphenicol is effective against a wide variety of microorganisms, but due to serious side-effects (e.g., damage to the bone marrow, including aplastic anemia) in humans, it is usually reserved for the treatment of serious and life-threatening infections (e.g., typhoid fever). It is used in treatment of cholera, as it destroys the

vibrios and decreases the diarrhoea. It is effective against tetracycline-resistant vibrios.It is also used in eye drops or ointment to treat bacterial conjunctivitis.

Mechanism and Resistance Chloramphenicol stops bacterial growth by binding to the bacterial ribosome (blocking peptidyl transferase) and inhibiting protein synthesis.

Chloramphenicol irreversibly binds to a receptor site on the 50S subunit of the bacterial ribosome, inhibiting peptidyl transferase. This inhibition consequently results in the prevention of amino acid transfer to growing peptide chains, ultimately leading to inhibition of protein formation.

Spectrum of activity: Broad-spectrum

Effect on bacteria: Bacteriostatic

GENERAL ANESTHETICS

General anesthesia often involves more than one drug to get different, favourable effects.
Premedication is often used to:
1. Treat anxiety - Benzodiazapenes
2. Reduce pain - Opiod anaglesics such as morphine
3. Produce muscle paralysis -E.g. Tubocurare
4. Reduce secretions
Induction of anesthesia is often done via intravenous anesthetics, which are quick and easy to administer.
Maintenance of anesthesia involves inhalation agents.

Prototype Agents:
Volatile Anesthetics:
•    Nitrous Oxide
•    Ether
•    Halothane
•    Enflurane
•    Isoflurane

Injectable Anesthetics:
•    Thiopental 
•    Ketamine
•    Etomidate
•    Propofol 
•    Midazolam
 

Codeine

Codeine is methyl morphine, with a methyl substitution on the phenolic hydroxyl group of morphine. It is more lipophilic than morphine and thus crosses the blood–brain barrier faster.

  • classified as a simple, or mild analgesic, codeine is often used in low doses as an oral analgesic has a much better oral/parenteral absorption ratio than morphine.
  • Effective for mild to moderate pain.
  • Constipation occurs
  • Dizziness may occur in ambulatory patients.
  • More potent histamine-releasing action than does morphine.
  • Should not be administered by IV injection.
  • Extremely effective antitussive agent and is used therapeutically for suppressing cough.
  • In contrast to morphine, codeine overdose can occasionally lead to the production of seizures.
  • Seizures can be treated with barbiturates.
  • Respiratory depression can be counteracted with Naloxone.
  • orally, 30 mg of codeine is equi-analgesic to 600 mg of aspirin, however, the effects of the two are additive, and occasionally synergistic

Class IV Calcium Channel Blockers
• Block the movement of calcium into conductile and contractile myocardial cells 
• Treatment: treatment of supraventricular tachycardia 
– Diltiazem 
– Verapamil 

Adverse Effects 
• Adverse effects associated with vasodilation of blood vessels throughout the body. 
• CNS – dizziness, weakness, fatigue, depression and headache, 
• GI upset, nausea, and vomiting. 
• Hypotension CHF, shock arrhythmias, and edema 
 

Oxycodone  
About equal potency to morphine. Very effective orally.

It is combined with aspirin or acetaminophen for the treatment of moderate pain and is available orally

Oxycodone is a semisynthetic compound derived from thebaine, with agonist activity primarily at mu receptors.

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

 Other sedatives: carisoprodol, cyclobenzaprine, and methocarbamol are used for muscle relaxation.

Baclofen
1. Used in spasticity states to relax skeletal muscle.
2. Occasionally used in trigeminal neuralgia.


Antihistamines (first-generation H1 receptor blockers)
1. Used for sedation (e.g., diphenhydramine).

Ethyl alcohol

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