by egpat 29-08-2017
Learning pharmacology is a daunting task for many of the beginners as they enter into a world of drugs all with different names, categories, mechanisms and pharmacokinetics. Remembering adverse effects of drugs shows its adverse effects on learning and drug interactions interact with your study. Yet the logic behind the subject makes more pleasure in learning, making pharmacology as one of the top subject in medical world. In this article, we will discuss the most useful tips for effective learning of pharmacology.
First thing to follow to visit the beauty of the subject is to catch the logic. Logical thinking always keeps your mind more active providing you a long term memory in your mind. In terms of pharmacology, we can illustrate logic as a magical drug. It binds to the logical receptors releases basic mediators that inter-link the concepts to produce a pharmacological response ---- A strong grip on the subject.
Let us be more clear with few examples.
Suppose you are studying calcium channel blockers. As you know, all calcium channel blockers are not equal even by their name or even by their location of action. For example, both verapamil and nifedipine are calcium channel blockers but differ in their selectivity. Verapamil is more selective for cardiac muscle whereas nifedipine for vascular smooth muscle. Another drug diltiazem is acting on both cardiac and vascular smooth muscle.
So, if you remember this logic, you can simply answer this question.
Which calcium channel blocker is NOT used for cardiac arrhythmias?
Verapamil Diltiazem Nifedipine
Undoubtedly, the answer is nifedipine. This drug is acting on vascular smooth muscle but not on the cardiac muscle. So it doesn’t decrease the rate of cardiac muscle hence not indicated for cardiac arrhythmias. That’s why class IV antiarrhythmic agents include only verapamil and diltiazem.
Now, let’s see another question on the same concept.
Verapamil is cardioselective, can it be indicated for hypertension?
Again answer is yes. Verapamil acts on cardiac muscle to decrease both rate and force of contraction. This decreases cardiac output as well as pumping pressure. Hence after load decreases consequently blood pressure decreases. So even verapamil is not acting directly on vascular smooth muscle, it can decrease the blood pressure indirectly.
Is that only difference between verapamil and nifedipine ?
No, they not only differ in their location of action but also differ chemically. Verapamil belongs to phenylalkyl amines whereas nifedipine belongs to dihydropyridines. Similarly diltiazem belongs to benzothiazepines. So, all these three drugs are chemically different.
Now we can summarise the concept in single statement.
Phenylalkyl amines like verapamil are cardioselective and dihydropyridines are vascular selective.❞
That’s fine. Again it is well known fact that all the drugs ending with suffix “-dipine” are dihydropyridines. For example, nifedipine, amlodipine, felodipine, isradipine and nimodipine all belong to dihydropyridines.
Why the suffix “-dipine” ?
The suffix dipine was taken from dihyropyripine.
To learn more on the important suffixes and drug categories, see
Now, let’s extend the concept.
Will verapamil and nifedipine produce same or different effects ?
Obviously, in few actions they are similar and in few they are different and even quite opposite. For example, both block calcium channels and both decrease blood pressure. But in other actions they are different.
Nifedipine, as it is a direct vasodilator, increases capillary permeability and produces ankle swelling. This effect is not shown by verapamil as it doesn’t act on vascular smooth muscle.
Similarly, verapamil acts on cardiac muscle decreasing heart rate leading to bradycardia. Nifedipine produces quite opposite effect, of course, by reflex action.
Nifedipine is a vasodilator that produces hypotension and decreases perfusion pressure. The later results in activation of baroreceptors and release of catechol amines which act on heart increasing the rate, leading to reflex tachycardia.
Verapamil produces bradycardia and nifedipine produces reflex tachycardia.❞
Next part in learning the concept is to understand the basics. If you know the proper reason behind a pharmacological action or adverse effect, you can easily visualise similar things anywhere you find in pharmacology and can easily justify the reason.
Salbutamol and ephedrine both are bronchodilators but later produces pronounced effect on blood pressure and tachycardia. Why?
The simple answer is selectivity. Salbutamol is a selective adrenergic agonist that specifically acts on β2 receptors which are abundant on bronchial smooth muscle. Hence it acts as bronchodilator and indicated in asthma.
On the other hand, ephedrine acts both on α and β receptors non-selectively. It increases blood pressure by acting on α1 receptors and produces tachycardia by acting on β1 receptors. Its bronchodilatory action is due to β2 receptors.
That’s why now a days, salbutamol is indicated for asthma but not the ephedrine.
Now, let’s dwell more deep into the concept. Ephedrine acts on β1 as well as β2 but former produces contraction of heart while later produces relaxation of bronchioles. How ?
First point we should note is that
All beta receptors are coupled with increase in cAMP.
So ephedrine acts both on β1 as well as β2 receptors to increase cAMP but former produces contraction and later produces relaxation due to their difference in contractile mechanism.
In another words,
cAMP produces contraction in the heart but relaxation in the smooth muscle.❞
So, whatever the drugs that increase cAMP levels in cardiac muscle produce contraction and in smooth muscle produce relaxation.
For example, drugs like dobutamine , amrinone and milrinone increase cAMP levels in the heart resulting in increased force of contraction hence used as cardiac stimulant in heart failure.
Similarly, drugs like theophylline, sildenafil and organic nitrates all increase cAMP/cGMP levels in smooth muscle and produce relaxation.
While you study pharmacology you should be highly familiar with all the drug names, pharmacological categories or classes by their drug targets. You should analyse the drug names and compare with similar or confusing drug names to make your concept more clear and transparent in your mind.
For example, you can observe two drugs amiodarone and amiloride which somewhat spell alike. The former is potassium channel blocker whereas the later is potassium sparing diuretic. So, both the drugs are pharmacologically different and you should not confuse with them.
Sometimes, learning classifications give you more information. For instance, you know drugs like ondansetron, granisetron and tropisetron are antiemetics classified as 5-HT3 antagonists. Similarly, drugs like sumatriptan, rizatriptan and elmitriptan are anti-migraine agents and classified as 5-HT1D agonists. Both are acting on 5-HT receptors but their sub receptors are different and one is acting as antagonist and another as agonist.
So learning classifications is very important to master the subject. At the following link you can find list of pharmacological classifications.
Interlinking the concepts from various topics make your memory more strong and less volatile. It let’s you compare and contrast the key points and bring you an analysed output into your mind which can be stored for a longer time. One of the advantage with this interlinking is it avoids confusion and retrieves the entire concept with a single key in your hand.
Suppose you are studying loop diuretics. These drugs on long term can produce ototoxicity leading to gradual hearing loss in the patients. Now search for any list of other drugs produce similar effect. You can find the well known aminoglycosides such as streptomycin, neomycin and amikacin etc. These drugs also produces ototoxicity leading to vestibular disturbances and hearing loss.
Loop diuretics and aminoglycosides both produce ototoxicity and hence should not be combined.
Some times you can also find the contrast in the concept. For example, ACE inhibitrs like captopril and enalapril produce renal failure leading to accumulation of potassium and hyperkalemia. Hence these drugs should not be given with potassium supplements when used for longer periods.
At the same time, polyene antibiotics like amphotericin produce hypokalemia hence should be given with potassium supplements.
Potassium supplements should be given with amphotericin but should be avoided with ACE inhibitors.
Reasoning a key point will increase your analysing capacity and your ability to apply the concept in the real time. You should ask yourself few questions while learning searching for the right reason at every key point.
Let’s have one example. AS we have already discussed earlier, increase in cAMP within the heart increases cardiac contraction. Is its inverse true? Drugs decrease cAMP within the heart decrease rate of contraction? Is there any such drug or mediator?
If you question like this, you can find the reasoning.
Yes, increase in cAMP within the heart increases contraction and a decrease in cAMP results in a fall in the rate of contraction. Drugs like adrenaline and dobutamine increase cAMP and hence a raise in cardiac contraction whereas acetylcholine decreases cAMP and produces fall in cardiac contraction. The former drugs are adrenergic agonists acting through β1 receptors and the later is a cholinergic agonist act through M2 receptors
β1 receptors are coupled with increase in cAMP while M2 receptors are coupled with decrease in cAMP both acting quite oppositely.
Visual presentation is always appealing, provides everlasting memory and even more informative, easy to revise rapidly compared with textual presentation. You can bring the entire concept into the nut shell within an infographic and can stress on key points for better understanding of the concepts.
You can use few shortcuts of your own yet logical and easy to remember. Undoubtedly, these graphs or flow charts can help you a lot in the exam and sometimes when you try to retrieve a particular point during your exams, you can visualise the point virtually along with its location whether left side or right side, either corner or middle you placed in the graph. That’s the power of visual presentation.
So, after preparing a particular topic, try to prepare by your own either a graph, flow chart or a table to summarise what you have learnt and to make you feel more confident.
Here is an example of such infographic.
So, these are the essential tips you can follow to make learning a fun and more interesting. Share with your friends if you like this post.