Advent of novel pharmacokinetic drug enhancers

You may no longer have to worry much about continually loading those pack of drugs in a bid to get cured of an ailment or worried about the easy degradation of drug by the liver enzymes.

Pharmacokinetic enhancers come in handy especially when a drug is easily metabolised (degraded by liver enzymes - the cytochrome family of enzymes) thus the need for continuous administration of the drug but bearing in mind that at some point, the receptors will activate their protective mechanism - tachyphylaxis.

Mechanism of action of pharmacokinetic enhancers

Pharmacokinetic enhancers are a class of drugs regarded as boosters. They help to boost the therapeutic potential of another's drug. They are always given together with the drug of choice.

Upon administration, the pharmacokinetic enhancer operates by interfering or blocking the breakdown of the other drug (especially those that are prone to quick or fast degradation by the liver enzymes).

Because the main or primary drug has been inhibited from quick or undesired degradation, this allows it to remain in the body at longer period and at higher concentration thus, enabling them to fully exert their therapeutic action.

A good example where this drug is used is in HIV treatment regimen. Typical example of a pharmacokinetic enhancer is the Cobicistat (commonly called Tybost). It is a CYP3A inhibitor basically used to enhance the systemic exposure of the HIV drugs - atazanavir or darunavir.

With pharmacokinetic enhancers, drugs especially HIV drugs stay longer and are much effective and are able to evade degradation by the liver enzymes.

Let's go into the second components of Pharmacodynamics

Post receptor effects

After the binding of drugs, events that occur afterwards are regarded as post receptor effects. Receptor must be available and free before a ligand can bind to them.

Just like we earlier established from the law of mass action, the more the receptors are occupied by a ligand or a drug, the greater their Pharmacodynamic effects. This concept is what is referred to as receptor occupancy.

This though doesn't necessarily mean that all the receptor sites must be occupied before a maximum effects is obtained.

Some use signal amplification to get a maximal effect thus sparring some receptor sites. This concept is what is know as spare receptors.

Note that, a drug's Pharmacodynamic effects can be altered or affected due to diseases like genetic mutation, Parkinson's disease, thyrotoxicosis (inflammation of the thyroid gland), myasthenia gravis, and even some type of insulin resistant diabetes mellitus (type 2 diabetes) etc.

Aging and the competition of other drugs for the active site of a receptor can also alter the drugs pharmacodynamic effects.

Drugs that inhibit other drugs during competition for the binding site on a receptor are generally referred to as Antagonist while those that promote binding are called Agonist.

Antagonist are also referred to as inhibitors while agonist are referred to as promoters.

In a situation where two drugs compete for the same active site of a receptor, it leads to what is referred to as competitive inhibition of lesser active drug that is unable to effectively compete.

This is why some drug combination are not always recommended.

You can read this article for more details about drug synergism and notable combinations of drugs you should never try.