Roxithromycin

It is used to treat respiratory tract, urinary and soft tissue infections. Roxithromycin is derived from erythromycin, containing the same 14-membered lactone ring. However, an N-oxime side chain is attached to the lactone ring.

Roxithromycin has similar antimicrobial spectrum as erythromycin, but is more effective against certain gram-negative bacteria, particularly Legionella pneumophilae.

When taken before a meal, roxithromycin is very rapidly absorbed, and diffused into most tissues and Phagocytes Only a small portion of roxithromycin is metabolised. Most of roxithromycin is secreted unchanged into the bile and some in expired air

PLASMA FRACTIONS:

a) Fresh frozen plasma.

b) Platelets.

c) Plasma concentrates.

d) Non-plasma recombinant factor concentrates.

On the basis of Receptors, drugs can be divided into four groups,

a. agonists

b. antagonists

c. agonist-antagonists

d. partial agonists

a. Agonist

morphine fentanyl pethidine

Action : activation of all receptor subclasses, though, with different affinities

b. Antagonist

Naloxone , Naltrexone

Action :  Devoid of activity at all receptor classes  

c. Partial Agonist: (Mixed Narcotic Agonists/Antagonists)

Pentazocine, Nalbuphine, Butorphanol , Buprenorphine

Action: activity at one or more, but not all receptor types

With regard to partial agonists, receptor theory states that drugs have two independent properties at receptor sites,

a. affinity

The ability, or avidity to bind to the receptor
Proportional to the association rate constant, Ka

b. efficacy

or, intrinsic activity, and is the ability of the D-R complex to initiate a pharmacological effect

Drugs that produce a less than maximal response and, therefore, have a low intrinsic activity are called partial agonists.

These drugs display certain pharmacological features,

a. the slope of the dose-response curve is less than that of a full agonist

b. the dose response curve exhibits a ceiling with the maximal response below that obtainable by a full agonist

c. partial agonists are able to antagonise the effects of large doses of full agonists

Dental implications of these drugs: 

1.    Adverse effects: gingival hyperplasia (phenytoin), osteomalacia (phenytoin, Phenobarbital), blood dyscrasias (all but rare)
2.    Drug interactions: additive CNS depression (anesthetics, anxiolytics, opioid analgesics), induction of hepatic microsomal enzymes (phenytoin, Phenobarbital, carbamazepine), plasma protein binding (phenytoin and valproic acid)
3.    Seizure susceptibility: stress can → seizures

Meperidine (Demerol)

Meperidine is a phenylpiperidine and has a number of congeners. It is mostly effective in the CNS and bowel

• Produces analgesia, sedation, euphoria and respiratory depression.
• Less potent than morphine, 80-100 mg meperidine equals 10 mg morphine.
• Shorter duration of action than morphine (2-4 hrs).
• Meperidine has greater excitatory activity than does morphine and toxicity may lead to convulsions.
• Meperidine appears to have some atropine-like activity.
• Does not constrict the pupils to the same extent as morphine.
• Does not cause as much constipation as morphine.
• Spasmogenic effect on GI and biliary tract smooth muscle is less pronounced than that produced by morphine.
• Not an effective antitussive agent.
• In contrast to morphine, meperidine increases the force of oxytocin-induced contractions of the uterus.
• Often the drug of choice during delivery due to its lack of inhibitory effect on uterine contractions and its relatively short duration of action.
• It has serotonergic activity when combined with monoamine oxidase inhibitors, which can produce serotonin toxicity (clonus, hyperreflexia, hyperthermia, and agitation)

TCI -Target Controlled Infusion

TCI is an infusion system which allows the anaesthetist to select the target blood concentration required for a particular effect and then to control depth of anaesthesia by adjusting the requested target concentration

Mechanism

Instead of setting ml/h or a dose rate (mg/kg/h), the pump can be programmed to target a required blood concentration.

• Effect site concentration targeting is now included for certain pharmacokinetic models.

• The pump will automatically calculate how much is needed as induction and maintenance to maintain that concentration.