Questions tagged [pharmacokinetics]

The branch of pharmacology studying the absorption, metabolism and excretion of drugs.

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How is Gliclazide SR and Metformin SR a rational fixed dose combination? And should it be taken before or after meals? [closed]

(Assuming the doses are right) since Gliclazide is a sulfonylurea which should be given before meals and metformin, a biguanide, which should be given after meals, isn't irrational due to different ...
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How are drugs distributed in regards to bone marrow?

I know that as volumes of distribution increase they correspond to the blood, then the vascular rich group (heart, kidneys, liver, brain if BBB permeable), then muscle then adipose. But things like ...
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What is the role of plasminogen used in the preparation of APSAC? (Anisoylated Plasminogen Streptokinase Activator Complex)

What is the role of plasminogen in APSAC, and how is there indirect activation of plasmin through APSAC? Reference https://www.sciencedirect.com/topics/chemistry/fibrinolytic-agent
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What happens to drug metabolism when CYP450 enzymes are presented with two substrates

What happens when two substances, both substrates for Cytochrome P450 metabolism, are both present in the bloodstream? For example, with sertraline and cannabidiol (CBD), if someone took a sertraline ...
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71 views

Is an X ml dose of a drug at 50% bioavailability roughly equivalent to a 2X ml dose at 25% bioavailability?

For the sake of simplicity, assume: The two doses are the same drug metabolized in the exact same way, and the only difference is the amount that reaches the bloodstream (and thereafter the brain). ...
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What is the motivation behind fluorinated pharmaceuticals?

From what little research I've done, it appears that a significant portion of modern psychoactive drugs are fluorinated in one way or another (for example, Buproprion, Fluvoxamine, or any number of ...
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329 views

Does Povidone-Iodine that penetrates through the skin stays in the body (cells, liver etc)?

Here it says on povidone-iodine: "Route of Elimination: Povidone-Iodine is intended for topical application and is not eliminated" "Clearance: Povidone-Iodine is intended for topical ...
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50 views

Does body fat percentage effect storage of fat soluble compounds?

Would a person with a higher body fat percentage store more of a fat soluble compound, or store for a longer time, than a person with a lower body fat percentage if they both consumed the same amount ...
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Is lysergic acid diethylamide (LSD) metabolized in the body?

Is LSD broken down into other compounds by enzymes or hormones? If so, at what point and where in the body does this happen? I researched several papers appearing in a google search, but unfortunately ...
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What is the concentration/molecules per cell of iodothyronine deiodinase in a cell?

I'm trying to parameterize an in silico model and need the approximate concentration (M), or molecules per cell, of iodothyronine deiodinase type II (D2) enzyme in a human cell, ideally a glial cell. ...
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2k views

How to make GABA pass the blood brain barrier?

I thought of methylating GABA at the gamma amino group in order to make it pass the blood brain barrier, but would it work? The goal is to make a sedative. Like GHB or benzodiazepines (I know that ...
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165 views

How did Shulgin take cognizance of the dosage of a new substance?

We know that Alexander Shulgin synthesized MDMA, 2C compounds and several other tryptamine derivatives and phenethylamines. But how did he find out that the average dosage of an unknown compound is X ...
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How could this molecule affect the body? (Lysergic acid derivative)

First of all, could you please help me name this molecule? I think the name of it is something like this: N,N-pentamethylene lysergic acid. Secondly, my main question is what could be the pharmacology ...
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Why was the intramuscular route selected for palivizumab administration to infants, instead of the subcutaneous route?

The majority of monoclonal antibodies administered by an extravascular route to adults are administered subcutaneously. Does anyone know or have hypotheses about the reasoning behind why palivizumab ...
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How does having spare receptors change ED50 in an irreversible agonist

Competitive antagonists increase the ED50 while the Emax remains the same. Irreversible antagonists do not change the ED50 while decreases the Emax. Katzung pharmacology, says that the irreversible ...
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437 views

Derivation for drug half life

The formula in textbooks for $t_{\frac{1}{2}}$ of a drug following first order elimination is generally given as $$t_{\frac{1}{2}}= \frac {\ln(2).V_d}{Cl}$$where $V_d$ is the volume of distribution ...
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212 views

Estimation of tissue-partition coefficients and clearance for liposomic nanoparticles

I am working on developing a PBPK model for liposomic nanoparticles used to deliver drugs to fells in the bloodstream. However, I do not have any in vivo data or in vitro data. Given only chemical and ...
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110 views

Cell nanoparticle dynamics within blood

I am trying to mathematically model the dynamics of a particular cell in circulation and its binding to another nanoparticle that is intravenously injected. The concentration of this cell is very low (...
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80 views

Can 5 alpha reductase inhibitor drugs work for life or do they lose effectiveness?

Do 5 alpha reductase inhibitor drugs like finasteride and dutasteride lose their effectiveness over time? Why do some drugs, like in an HIV regimen, work for a prolonged time without tolerance whereas ...
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570 views

calculate elimination rate constant [duplicate]

A patient diagnosed with cancer takes antiproliferative drugs. Suppose the intake of drug(dose) is 250mg and excreted amount 125 mg. Amount of excreted drug as metabolites 1 and 2 are 75mg and 50mg. ...
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276 views

Why is alcohol such a weak drug?

Most day to day drugs such as caffeine and paracetamol require a dosage in milligrams to have the desired effect. Why then, does it take many tens of grams of alcohol to have a tangible/noticeable ...
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355 views

Difference between the inactivation of neurotransmitters and hormones

Neurotransmitters must be somehow removed from the synapse once they’ve produced a post-synaptic potential, whether it be through enzymatic breakdown, diffusion, reuptake or another mechanism. However,...
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876 views

How to determine sensitivity in a dose-response curve?

In a dose-response curve the % inhibition can be plotted against concentration antagonist. In our case, the effect of the antagonist is tested in different genetic variants of a microbe. When trying ...
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How do macromolecules (large drugs) in the eye reach the bloodstream and what are the relative significances of these pathways?

I am considering the elimination pathways for antibodies (50-150 kDa) from the vitreous humour to the blood stream. My overarching question is what is the most significant route such antibodies could ...
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Infection of urinary tract if the pH of urine is made alkaline

It is very well known that drugs like phenobarbiton,morphine are unionized, lipid soluble.So,in case if there is toxicity due to these drugs,the only way to save the patient is make the pH of urine ...
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4k views

How to calculate biological half life of a drug that is dose dependent?

I would like to calculate the half-life of a biological drug. This biological drug is said to have a biological half-life of: ...
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349 views

Given an EC50 value, how do I reproduce the sigmoidal curve from which this was calculated?

All-trans retinoic acid (atRA) is a potent ligand for a nuclear receptor called retinoic acid receptor alpha (RARa). The concentration of atRA at which RARa is half maximal is 19nM. The dose-response ...
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282 views

Is there a specific mechanism for the delivery of pain medication?

For example, when one takes aspirin or ibuprofen does the chemical get dispersed to all pain receptor? My question really is, how does the chemical know where to target in the body? I figure wherever ...
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Protein-Bound Drugs in Kwashiorkor

Kwashiorkor is characterised by decreased serum protein (including serum albumin) due to poor dietary protein intake. What is the effect of this lowered serum protein on highly-protein-bound drugs? ...
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4k views

How does food intake affect medicine? Why pill instructions recommends taking them before (after) meal?

Even simple vitamins seem to have this in the instruction. Why is is so? Is there some simple model of how do pills interact with food? Does it depend on the food type? (What about drinks?) Should ...
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negatively charged albumin as major carrier of acidic/negative charged drugs in blood

I reading that orsomucoid (alpha-1-acid glycoprotein) is the major carrier of positively charged (basic) drugs in the blood, while albumin carries negatively charged (acidic) and drugs with neutral ...
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Anesthetics, specifically inhaled anesthetics

I have had a look at previous inhaled anesthetics and many of them appear to be fluorocarbons. What could be the mechanism behind fluorine's anesthetic properties? Is it the specific bonding pattern ...
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Does THC excretion increase if urine volume increases?

In regards to the body metabolizing and excreting THC: if urination is increased as a result of drinking lots of fluids, does that mean that more THC is leaving the body? To rephrase the question, is ...
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1answer
353 views

What is the most common way of administering loop diuretics and what is their time course of action?

I am reviewing some material on loop diuretics, and I am curious to know how these drugs are administered. Also, I am interested in knowing their time course of action once they are administered into ...
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Why do different pain killers have different effects on people?

I've noticed some pain killers working great for me, while others have no effect. Works for me Aspirin APC † Naproxen Doesn't work for me Paracetamol Diclofenac Tramadol I doubt there is ...
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Thermochemistry of gabapentin

So I am taking a new class at my institution called Theoretic Nuclear Thermochemical Pharmacology, (I know big name, it's an elective from a real pioneering fronteirsman in our department :P) and I am ...
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80 views

How are drug metabolism and detection related?

If someone is taking treatment for a psychiatric disorder (e.g. diazepine), then would traces of the metabolized drug be detectable in their sweat or saliva? Any links to resources regarding this, ...
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Pharmacokinetics: why do certain drugs follow zero-order kinetics?

I understand that alcohol and phenytoin are two examples of drugs that follow zero-order kinetics. Why do these two particular drugs follow zero-order kinetics as opposed to first-order kinetics?
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886 views

Pharmacology Half Life Calculation

I'm really stuck on this question. I'm being asked to find the half life of a drug. The Vd is 50L/kg. The clearance is 0.1 L/hr/kg. The patient weighs 70 kg. Equation is: T1/2 (halflife) = 0.693 * ...
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What is the physiological difference between snorting/swallowing cocaine

I know that mucosa inside the nose absorbs cocaine molecules when snorting cocaine, but what difference is there compared to swallowing? Also more cocaine administration equals more cocaine molecules ...
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Why can't sodium butyrate be delivered orally in humans and other mammals?

I think I know why -- bioavailability problems but since I have no firm evidence to support this theory I thought I would ask the biology stackexchange community for their input. I'd like some firm ...