Drug Release

Drug Release

  • Anwar A Hussain added an answer:
    Is it possible for cumulative drug release to exceed 100%?

    Paracetamol suppositories made with PEG 4000 and PEG 6000 as suppository bases undergo dissolution test. After 45 minutes, both batches have mean % of drug release that is higher than 100%.

    PEG 4000- 150% and PEG 6000- 120%

    Why does the cumulative drug release exceed 100%? Is there error during measuring of absorbance or is it some form of degradation or hydrolysis of the medicine during manufacture/storage?

    Anwar A Hussain

    Thank you , The pKa of Paracetamol is more than 9 , and that is why it is a weak acid. The pKb is 3.7. So Paracet. exist in unionized form till pH almost 9. Make a stock solution in a spectral grade methanol , transfer the same volume to six flasks add buffers ranging from pH 3,5,7,8,9, and 11. Immediately scan the solutions using the corresponding  buffer in the blank cell. When you scan start with the high pHs before oxidation starts which takes place at high pHS. for now let is forget the peroxide issue, it is a long story,. Chose a wave length where the PEGS have no absorbance. As long as you get a linear plot between the conc. and the absorbance at that wave length you are ok. Use the same dissolution medium in the reference cell as long as the PGEs have no absorbance at that wave length. Let me know what happen and we go from there . Glad to help.

  • Tarek Mosaid Bedair added an answer:
    Can anyone suggest the best way for this study as i can't see the sirolimus peak after HPLC at 278 nm?

    I coated the metal surface with a mixture of PLLA and sirolimus and i want to study the drug release in human plasma. The loading amount was 125 ug per sample. For the drug release, i immersed the sample in 1 ml of plasma solution and after predetermined time 1d, 3d, 5d, ....... i can't measure the amount of the released sirolimus. could you please inform me how to extract the sirolimus from the plasma solution or any other way?

    Thank you in advance

    Tarek Mosaid Bedair

    Thank you all of your advice

    After searching, i found that the sirolimus is not stable in human plasma solution as the half-life time of sirolimus is only 6 hrs.

  • Delly Ramadon added an answer:
    How do I calculate cumulative drug release?

    I'm doing drug release using Franz diffusion cell. The medium is PBS. I'm taking 500uL samples at predetermined times and replace the amount taken with fresh PBS to maintain the sink condition. I'm not sure how to do a cumulative release plot (amount permeated vs time) because the absorbance data that I've got is going up and down( is that normal?). 

    Delly Ramadon

    The data should be calculated using the real amount in the receptor compartment. You should follow an equation in the article above.

  • Bikash Debnath added an answer:
    What are the problems for gentamicin derivatization?

    I'm working on controlled release of gentamicin from microspheres. To measure the drug amount I use derivatization method which includes ortho-phthalaldehyde, beta-mercaptoethanol, methanol in 0.04M sodium tetraborate. But after derivatization, I couldn't obtain any measurement at 333 nm neither peak. What is the problem that I did wrong?

    Bikash Debnath

    Gentamicin is the cheapest and the first line aminoglycoside antibiotic. Intake the Gentamicin for serious gram negative bacillary infection it has gives relatively more nephrotoxic effect in human. 

  • Nilani Packianathan added an answer:
    How do I detect hydrophobic drug such as curcumin in PBS?

    How can I detect curcumin in PBS? I've run through my samples through HPLC twice but I couldn't detect any curcumin when the absorbance could be detected when I run my samples through UV. I'm doing a drug release study for this. 

    Nilani Packianathan

    Curcumin can be separated from curcumin mixture (a mixture of curcumin, demethoxycurcumin and bisdemethoxycurcumin) by column chromatography by adsorbing the mixture on silica gel using mixtures of solvents like dichloromethane/acetic acid or methanol/chloroform to yield three different fractions. The curcumin fraction is further purified on silica gel using chloroform/dichloromethane and ethanol/methanol mixtures as eluents . Methods for the detection and estimation of curcumin have mostly employed the high performance liquid chromatography (HPLC) technique. In general reverse phase C18 columns are used as stationary phase and different gradients of solvents containing acetonitrile/water or chloroform/methanol have been employed as the mobile phase [21–24]. For detection of curcumin, absorption detectors in the wavelength range from 350 to 450 nm range or in the UV region using a common detection wavelength in the range of 250 to 270 nm is simple and extremely useful.

    HPLC-diode array and fluorescence detection methods have also been used by several researchers. Liquid chromatography-coupled mass spectrometry has been another versatile tool for detecting curcumin. Of all these the most sensitive methods for detection of curcumin (up to 1 ng/mL) is by fluorescence, by exciting in the 400 to 450 nm region. High-performance-thin layer chromatography methods using aluminium plates precoated with silica gel as stationary phase and chloroform-methanol as solvent have been very useful for both detection and separation.

    Pls refer to research article stated below for further information:

    The Chemistry of Curcumin: From Extraction to Therapeutic Agent
    Kavirayani Indira Priyadarsini

    Molecules 2014, 19, 20091-20112; doi:10.3390/molecules191220091


  • Jaywant Pawar added an answer:
    How can I develop the dissolution medium of poorly water soluble drugs apart from official media given in USP/BP?

    Whether it is necessary to compare my developed formulation with the innovator drug release profile in respective dissolution media?

    How to develop a dissolution media for existing API? I want to study How is the technology or polymer composition helping us to improving drug release pattern?

    Jaywant Pawar

    Thank you Vladimir and Mubashar Rehman Sir for the detailed information. 

  • Mubashar Rehman added an answer:
    Which technique do you suggest to study release of Sorafenib from sorafenib loaded lipidic nanocapsules?

    Hi there. I have encapsulated Sorafenib in lipidic nanocapsules with size of  50 nm. I have planned to study drug release by Sink Conditions through using dialysis membrane (MWCO: 100kD) in "PBS-1% Tween 80" as medium. The problem is that approximately all the released sorafenib attaches on the membrane and does not enter to the medium. What do you suggest to solve this problem? Can I add something like blank lipidic nanocapsules into the medium to increase the mobility of the drug? Thanks a lot.

    Mubashar Rehman

    Can you use any other method than using dialysis tube? If your dissolution study is flexible, you may take very low amount of lipid nanoparticles in eppednorf tubes and add dissolution medium. Place these tube in your test conditions. At different time points, take out one tube. Separate lipid nanoparticles and measure amount of Sorafenib released till this time. This method is sometimes used to determine solubility of proteins.

  • Manuel Roman Pina-Monarrez added an answer:
    Can any body help me to learn how to fit drug release data into Weibull Function in Excel?

    Hi all. I need to fit my drug release data into Weibull function to know about the mechanism of drug release.

    The formula for weibull function is F = 1 − exp(−atb). where F is the drug fraction released at time t, and a and b are constants. b, as a shape parameter, is characterized as exponential (b = 1), sigmoidal (b >1), or parabolic (b < 1).

    Can some one help me HOW to fit or put my drug release data into this formula using microsoft excel sheet?

    Manuel Roman Pina-Monarrez

    Nauman, I am familiar with Murat advised, Only, in the estimation of ln(-ln(1-F(t))), since F(t) is estimated by the median rank given by the Benard's approximation given by F(t)=(i-0.3)/(n+0.4), then the sample size n has big impact in the estimated b and a parameters. Thus, in order to select the right n, you has to determine first the desired or expected reliability percentile R(t), and based on R(t), determine n as n=-1/ln[R(t)]. (see eq.(35) of the reference paper given below).

    In particular, since b is completely determined by the standard deviation of the lifetime data [eq.(41)], and a is completely determined by the mean of the lifetime data [eq.(46)], then, selecting the right n is determinant to accurately estimate the b and a parameters.

    My paper where these issues are addressed and solved is "Weibull and lognormal Taguchi analysis using multiple linear regression". which is uploaded to RG. Please observe that in addition to estimate n correctly, the paper also gives the method to determine b and a for a desired combination of the factors that determine your life times. Thus, if you have the factors that determine the lifetimes you can use them in the estimation of the related Weibull family. Any question related to the paper content or how it could be implemented by using your data, please let me know.

    Good luck.

  • Sonal Mazumder added an answer:
    What concentration of nanoparticles should be used for release studies - Is sink condition the determining factor?

    How important it is to maintain sink conditions during drug release studies from nanoparticles? What should be the concentration of pure drug and drug in nanoparticles in the buffer to start with? Is there a way to decide that? I have drug incorporated in polymeric nanoparticles.

    Sonal Mazumder

    Got it!

    Thank you.

  • Adeel Masood Butt added an answer:
    Why is important to lyophilize drug-loaded micelles before drug release curves?

    I have drug loaded polymeric micelles, and i read in some papers that lyophilized and other non-lyophilized before the drug reléase.

    Adeel Masood Butt

    Usually we lyophilize the samples for stability and storage. As you can not keep the micelles in solutions for long time (for storage), so it is better to freeze-dry. Then you can use the freshly prepared micelle solutions for release experiments or for any other required assay.

    Hope this helps

  • Poulami Majumder added an answer:
    How do I assure a sustained release for a weakly basic hydrophobic drug?

    I am trying to make a sustained release system of a hydrophobic drug (significantly soluble in DMSO only, not in methanol/acetonitrile/choloroform, etc). The drug is NOT aromatic but has a nitrogen and pka ~ 8.3. It always leads to a burst release when I tried to encapsulate within neutral liposomes composed of DOPC/DOPE/Cholesterol, etc. I dissolved the drug in DMSO, mixed app. amount (10:1 lipid: drug in w:w) with other co-lipids, swelled overnight with water and removed unentrapped drug by centrifugation. Encapsulation efficiency was ~50-60%. But it was released entirely within 3 h. Then I tried to use the citrate salt of the drug (water solubility ~ 1 mg/ml) for remote loading into the neutral liposomes (DOPE/DOPC in 1:1) after forming transmembrane pH gradient. Now, I found no encapulsation at all. Please suggest something so that I am able to reduce the burst release for the drug. Any help is appreciated. Thanks!

    Poulami Majumder

    Hi Rahul,

    Many thanks for your extensive reply. My drug is a nitrogen base containing pyrimidine and piperidine rings with a mol wt of 313 for the free base form. The drug is really leaky because my first trial was to load it into a hydrogel for making a sustained release system and that too did not work for the drug, so I decided to load into the liposomes first and then put the liposomal drug into the hydrogel.

    I tried the following:

    1. to load the free base form in the lipid bilayer. It shows ~ 80% encapsulation.

    2. Loaded an inclusion complex of the drug with beta-cyclodextrin into liposomal aq core with ee of ~ 60%

    3. Loaded the water soluble citrate salt of the drug (solubility 1 mg/ml) into the aq core and had ee of ~ 50%.

    But none of these does not lead to any improvement of the burst release profile when I put the liposomal drug into the hydrogel. So, I decided to check with transmembrane gradient.

    Many thanks for your suggestions. Hopefully this time it would turn out well.

  • Lefnaoui Sonia added an answer:
    How can I increase solubility of my hydrophobic drug (Log P = 5.09) for in vitro drug release and permeation study?

    I've prepared nanoemulsion and need to measure the release and permeation of that formulation using franz diffuiosn cell. I've found some of the researchers added SDS (sodium dodecyl sulphate, 2%) or ethanol in PBS 7.4? Which one is the best? Is there any guideline that I can follow for this experiment? My drug is very hydrophobic (0.039 ng/ml - solubility in water) and high solubility in methanol and ethanol. Thanks a lot.

    Lefnaoui Sonia

    L'ethanol est plus approprié pour votre étude.

  • Çağla Çibuk added an answer:
    What is the reason that the release does not continue? (controlled drug release, HPMC matrix, cefazolin)

    I am working on drug delivery behaviour of cefazolin by using HPMC as a matrix. In vitro release of cefazolin from HPMC carried out at 37 C in SBF pH 7.4. 55% of the loaded drug was released within 6 hours and after that we did not observed any release. We did not explain this peculiar behaviour.
    We think that either cefazolin are trapped within the HPMC matrix or it degrades and we can not observe the change in concentration.

    Çağla Çibuk

    Thanks to all of you for your answers, I will consider your thoughts.

  • Nguyen Thuy-Duong Thi added an answer:
    Ask for recommendation of using Tris-HCl solution for releasing test?

    I want to check the releasing rate of Ca from my bio-material sample by using Tris-HCl solution (pH=7.4). However, I can not figure out which concentration of Tris-HCl solution is close to body fluid. Could you give me some recommendations?

    Any help would be respected.

    Thank you!

    Nguyen Thuy-Duong Thi

    I want to detect the release of Ca from bioactive surface in physiological conditions without inorganic components. The release (dissolution) of Ca in SBF or other solution containing inorganic components effects on the release of Ca due to other phenomena: precipitation and ion exchange, Thus, Tris-HCl solution looks like to be suitable... 

  • Ahmed Agiba added an answer:
    Can it be claimed that cyclodextrin based polymer shows enhanced drug release due to inclusion complex formation?

    I have prepared a polymer using cyclodxtrin as a crosslinker. After loading of a drug into cyclodextrin based polymer matrix, the drug showed enhanced drug release as compare to polymer without cyclodextrin. There are reports which describes that my model drug forms inclusion complex with cyclodextrin.

    Ahmed Agiba

    inclusion complexation of a drug with B-cyclodextrin loaded into a hydrophilic mucoadhesice polymer is considered one of the methods to ehance solubility, bioavailability and stability of drugs, particularly poorly soluble drugs.

  • Jeffrey J Weimer added an answer:
    How can I determine the n exponent of korsmeyer peppas?

    If I have an equation of korsmeyer chart ( log cumulative %drug release and log time) is y = 5.1 x + 3.2 and R2 = 0.8038

    how can determine the n exponent to determine the mechanism of release ?

    Jeffrey J Weimer

    "You can take two points of time with their respective Mt to complete the equation and isolate the k in each."

    Two points may give the slope and intercept of a line or solve two equations for two unknowns. It is however a sloppy approach to take in this case. The suggested method should be used only to obtain a first guess. The rigorous approach for a publication-quality report is to use non-linear regression fitting methods to get the parameters and their uncertainties.

    We have inexpensive (free), intuitive, user-friendly desktop computational applications today that can perform rigorous data analysis and return fitting values with their confidence limits in the blink of an eye. Why do folks still insist on doing data analysis as though all they have with them is an abacas or hard-copy graph paper?

  • Anu Rosina added an answer:
    Can we crush a sustained release tablet?
    Is it possible for a person to crush a sustained release tablet for fast action?
    Anu Rosina

    crushing a sustained release tablet affects the drug release in which the drug is designed to release slowly in a specific period of time & results in rapid release of the drug and also affects site specific delivery of certain drugs

  • Abbas Raza added an answer:
    Does anyone know about silastic tubing for implants in mice?

    Hi there,

    i am looking for some guidelines to using silastic tubing for implanting hormones in mice. I need to provide 50ug of drug released every day. Has anyone worked with them and would be willing to guide me the required specifications for this dosage? 



    Abbas Raza

    that's an excellent piece of info. thank you!

  • Sree Gayathri asked a question:
    How do I analyze the mechanism of drug release-rate kinetics? Is it first order or zero order kinetic by looking at the drug release results?

    How do I analyze the mechanism of drug release-rate kinetics? Is it first order or zero order kinetic by looking at the drug release results?

  • kRISHNA CHAITANYA Telaprolu added an answer:
    In drug release calculations, does dilution factor have any role in it?

    nanoparticle drug release


    yes that's correct and follow the same for entire drug release, notice down the conversion to mg or micro gram as per your std calibration curve

  • Mohammed adnan Mezaal added an answer:
    Whats the difference between cumulative drug release(%) and drug release(%)? How might I calculate drug release using a formula)?

    I am studying nanoparticle drug release

    Mohammed adnan Mezaal

    You may read this article . I have explained in details the kinetics of drug release in the aquous media. If you need further help let me know please. Layered Double Hydroxides Nanohybrid Intercalation with Folic Acid Used as Delivery System and their Controlled Release Properties. DOI: 10.1007/s13369-012-0403-2. M A Mezaal

  • Sachin Surwase added an answer:
    What would be the hydrophilic drug release pattern from PEG-PLGA polymer? Will it be decreasing since its very soluble in water?

    Nanoparticle drug release.

    Sachin Surwase

    You can say it as a "burst release" due to adsorbed or weakly bound drug.

  • Cristian Hugo Gil added an answer:
    Is there anybody working with Norgestomet / Altrenogest controlled release formulations?
    We are studying release profiles in PLGA and silicon implants. Any help would be great for us.
    Cristian Hugo Gil

    We think we understand shape and structure from carrier. Question is, we are not sure of amount and use of Propyleneglycol in matrix. As it is highly hydrophilic, maybe it is used to make device more hydrophylic, or to dissolve Norgestomet in it. Any help on this subject, I shall appreciate very much. Thanks a lot!

  • Raphael Henrique Marques Marcilli added an answer:
    What are the causes of burst drug release ??

    i want to know the factors control the burst effect in a modified drug release systems ?

    Raphael Henrique Marques Marcilli

    adicional information
    Temperature, pH or some reductor or oxidizing agente can promote the bust release for example, the critical point is to know the release mechanism of your drug. I've worked with S-nitrosothiol group releasing, in this case a reductor agents, like ascorbic acid, promote a bust release by the reduction of bond S-N.

  • Shafi ullah Khan added an answer:
    What will be the release mechanism of the drug and what will be the effect of pH on drug release?

    If polyoxometalate (anion) is electro-statically binded with the a cationic polymer using acrylic acid as a monomer.

    what will be the release mechanism of the drug and what will be the effect of pH on drug release?

    Normally a drug is loaded in free form in polymeric network (hydrogel) and release mechanism is by diffusion process. Here the drug by itself is the part of hydrogel system and is electro-statically binded with the polymer.

    Shafi ullah Khan

    Thanks Alot Raphael Henrique Marques Marcilli,Jeannine Coburn and Abdelkader BOUAZIZ 

  • Saadi Bin Qasim added an answer:
    Why do we take the absorbance of drug once during dissolution of capsule? What would be the equation for calculating the comulative % of drug release?

    Why do we take the absorbance of drug once during dissolution of capsule? What would be the equation for calculating the cumulative % of drug release?

    I did the percentage of drug release for amoxicillin capsule.

    Saadi Bin Qasim

    Hi Rashaduz,

    This is one of the most mindboggling questions I cracked, Preffered to stick to % recovery though

  • Abbas Rahdar added an answer:
    Drug Release Profile
    I work on temperature sensitive liposomes and I encapsulate calcein to get the release profile. But each time I measure the dye release using fluorometer, the fluorescence intensity decreases as I increase the temperature.

    Can someone suggest to me a better method to measure the drug release? How can I ensure that free calcein has been completely removed after purification? Gel filtration alone doesn't work for me.
    Abbas Rahdar

    Dear Mercedes,

    please sugget me several fluorescent dye that be soluble in water and micelle systems.

    All the best,


  • Mala Menon added an answer:
    How can I calculate the % of drug released during dissolution studies?

    Can anybody provide me the equation by which i can calculate the percentage of drug release during dissolution of a solid oral dosage form?

    Mala Menon

    Dear Ashraf,

    1) You need to have a suitable analytical technique (UV spectrophotometry or HPLC) and standard plot of your drug  in the dissolution medium you are using for the release studies.

    2) During  dissolution studies you will be withdrawing various aliquots and analyzing the drug content in them by your method.

    3) From calibration/std plot find out amount in the withdrawn aliquots.

    4) By simple mathematics you can calculate the amount in total dissolution medium  (900ml). From 2nd reading onwards, you need to add the cumulative amounts released in the withdrawn volumes.

    5) Then you can compute 5 released at each time point based on total drug (label claim) in your solid oral dosage form.

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