I wonder why are you using a vernier callipers. You should have used a plethysmometer for this purpose.

Now as you have started the study, you can find a uniform scale for all the measurements. I think the volume of liquid displaced by the hind paw would be more useful rather than ur present approach.

Thank you Dr. Alok Nahata.

The problem is I am assessing the efficacy of a topical herbal drug in an aqueous gel base.

when we tried assessing using plethysmograph the gel got washed out.

That was the reason why we looked for an alternative method.

Then we found few articles using vernier caliper. here they have assessed the thickness of paw at 0 and 3 hours of injection of carrageenan. I wrote to the author regarding this. But the author did not respond.

But another author asked me to send the data. I sent a part of data. I did not get reply.

The question is when we are estimating the volume in millimeters using caliper's what is the land mark that has to be used.

we considered rat paw to be square and measured length x breadth x height for all the groups..

We have used fixed landmarks for the measurement.

When we are doing statistical analysis %ge reduction in edema is say +10% in the standard group and - 24% in the test group using the standard formula

Percentage inflammation = {v-vi/vi} x 100

Vi = 0 hour reading

V= 3 hour reading

Percentage inhibition = {1- Percentage swelling of drug treated group} x 100

Percentage swelling of control group

This value is making interpretation difficult.

Can you help me out with this?

Tell me one thing. You are using this 0 and 3 hr protocol just because you can't use plethysmometer and you have to use VC or you would have followed this protocol with plethysmometer also.

O and 3 hour protocol was used with the plethysmometer at the beginning . Then we used 0, 1 2 3 upto 6hours. That is when we identified the problem. then on consultation with the head of Pharmaceutics who suggested to try alternate method we went ahead with 0 and 3hr protocol with VC. The protocol would have been same even if it was with the Plethysmograph.

“A man's errors are his portals of discovery.” James Joyce. I have given all the information to you. I guess if you have answers to my question please give it.

Can you provide the reference you are following for the method using the Vernoer Callipers. A full text article is desired. I want to go through it then I can probably suggest something to you.

Otherwise if possible can you make some changes in your formulation so that it doesn't wash off while using. Herbal drug can also be incorporated in a ointment form in an oily base also so that it is not washed off during the experiment. You can also go for oral administration of the same drug without any problems. This are the last options however. Lets see.

thanks. The Tenoxicam gel PDF which i have attached, is the key article on which I based my methodology. later articles with vernier caliper was used to modify design.

I could add just one attachment. now I am attaching the article on vernier caliper. The main purpose of using our gel is in the mouth around the tooth to treat periodontitis. So we either need an in situ gel or water based aqueous gel which will remain in the gingival sulcus around the rat molars. These are the preliminary studies which I have to do as per the protocol approved by the institutional committe.

I do not know if my idea is right . I am sharing it with you. Can I consider rat paw as two cones superimposed on one another with a common base at the region of metatarsals? But It will mean an entirely different formula. I felt measuring just thickness on the paw in the horizontal plane a unidimensional phenomenon. That is the reason while estimating the volume using VC we considered the rat paw to be a rectangle and we calculated Length x breadth X height.

I am not able to attach the entire pdf so I have copied and pasted a part of it:

PREPARATION AND EVALUATION OF ANTI-INFLAMMATORY ACTIVITY

OF GUGULIPID-LOADED PRONIOSOMAL GEL-CHETNA GOYAL et al. publihed in Acta Poloniae Pharmaceutica ñ Drug Research, Vol. 68 No. 1 pp. 147-150, 2011

Anti-inflammatory activity

The anti-inflammatory activity of gugulipidloaded proniosomal gel formulations was evaluated by the carrageenan-induced rat hind paw edema method (13). The experimental protocol was designed and approval of Institutional Animal Ethics Committee (IAEC) (Reg. No. 0436) was obtained. Healthy Wistar rats of either sex weighing between 150ñ200 g were obtained from the diseasefree small animal house of CCSHAU, Hisar. The animals were housed in institutional animal house

under standard conditions with free access to food and water. Anti-inflammatory activity of the gugulipid-loaded proniosomal gel was compared to the marketed gel of diclofenac (VoveranÆ Emulgel). Fifteen albino Wistar rats were divided into three groups of five animals each as follows:

Group 1 (Control group): animals were treated

with plain proniosomal gel.

Group 2 (Standard group): animals were treated

with diclofenac gel B.P.

Group 3 (PNG2): animals were treated with

gugulipid loaded proniosomal formulation.

Inflammation was induced by sub-plantar carrageenan injection and after 1 hour, formulations were applied topically on the inflamed paw of rats by gently rubbing with index finger and the volume of the paw was measured (12, 13). The thickness of paw was measured at 1 h time intervals till 5 h after carrageenan injection. A digital vernier caliper (Aerospace, China) was used for measuring paw thickness of rats. The percentage inhibition ofinflammation was calculated by the following formula:

Percentage inhibition = [(C-T)/C] ◊ 100]

where C = control paw edema, T = test paw edema.

I think you should also focus on paw thickness rather than volume as all of them have done. Because it is impossible to find the volume using a vernier callipers. You can measure thickness, i agree. but volume, not feasible. For that you need a plethysmometer. So better u also measure paw thickness and interpret your results with that only.

Another approach is if you can cover the rat paw with such a material which covers the gel with itself (doesn't allow it to wash off) and also allow thickness measurement through plethysmometer, then also problem is solved. Alternatively you can apply the gel in a plaster like a bandage and stick it on rats paw. This will also make the measurement possible.

Just try what is feasible at your end. Some innovations need to be done in your case :)

Gud Luck

thanks a lot for your tips.

Regards

Rajesh