2nd term practical labs ( lab 1)
Effects of drugs on blood pressureBlood pressure : a physiological variable, regulated within a narrow range so to provide an adequate perfusion of the tissues.
BL.PR= CO x PR
CO=HR x SV
SV depend on contractility & filling pressure
Filling pressure depend on blood volume and venous tone.
PR depend on arterial resistance.
Main controller of blood pressure
1- sympathetic activity through:α receptors on smooth muscles of blood vessels affecting PR.
β receptors affecting CO.
2-Renine system by affecting GFR & increasing blood volume.
Drugs reducing blood pressure (antihypertensive drugs)
Drugs increasing blood pressure
1- steroids.2-β1 agonist ( ex:dobutamine)
3-α2 blockers(ex: yohimbin)
4-D2-blockers( ex:metoclopromide)
5-Ephedrin.
6- Amphetamin.
Drugs used
1- Ephedrine (15 mg): is a mixed acting adrenergic agonist, it induces the release of NA from presynaptic terminals and activates adrenergic receptors on the postsynaptic membrane.It raises both systolic and diastolic bl.pr by vasoconstriction and cardiac stimulation.
2- chlorpromazine (25 mg):
A neuroleptic drug it blocks D2, α, muscarinic, 5HT & H1 receptors.3-placebo (glucose powder)
Procedure
Double blind placebo controlled technique.Double blind: both the patient and the investigator are kept in ignorance of the treatment.
It is helpful in:
1- to distinguish pharmacodynamic effects from psychological effects of medication.
2-to distinguish the drug effects from disease fluctuations.
3-to avoid false –ve results.
Placebo: is a drug without specific biological activity for the condition treated.
It is used for:
1-as control in scientific evaluation of drugs.
2-to benefit or please the patient by psychological means.
1-In each group 3 students will be volunteers and 3 will be investigators.
2-measure blood pressure every 2 minutes for several times to establish baseline recording.3-using the double blind technique, the volunteers is given one capsule A,B or C orally.
4-measure the blood pressure every 10 minutes for 30 minutes.
5- At the end of the exp. the code is opened.