Xanthines ,fluidtherapy & mercurials

Presented by :Dr Sunil Boghia

MVSC, BVSc & AH

Xanthines

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These drugs stimulate cardiac functions. Theirdiuretic activity may stem from theresultant increase in renal blood flow andthereby an increase in glomerular filtration rate.

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They also exert a direct action on the renal tubule.Renal response is manifested by anincrease in levels of sodium and chloride in urine.

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• There is no significant change in the urine pH andpotassium excretion appears to berelatively unaffected.• Examples are: Caffeine, Theophylline

Mercurials

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• Diuretic action of mercurials is associatedwith sulphydryl groups and so they inactivatethe sodium transport mechanism of thenephron.• For clinical use, mercurials are obsolete

Alkaslisation of urine

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• Alkalinising agents reduce the irritation of aninflamed urinary tract and discourage thegrowth of certain organisms like E.coli.• Urine can be made alkaline by sodiumbicarbonate intravenous administration or bypotassium citrate oral administration.

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Sodium or potassium citrate is metabolised toform a stable cation (Na+ or K+) and a labileanion (citrate). • Citrate is taken up for use by theTCA. The Na+ or K+ is excreted with the most commonanion (HCO3- • Hence, there will be alkaline urine.

Administration & USE

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To decrease the adverse effects ofsulphonamides alkalinisation is useful.Sulphonamides

are generally insoluble in acid urine. They maythus precipitate out and crystallise.Therefore, to increase solubility, the urine ismade more alkaline.

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To increase the excretion of acidic drugs likeAspirin, salicylates and barbiturates.• Alkalinisation of urine increases the antibacterialactivity of aminoglycosides in urinary tractinfection.

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Alkalinisation of the urine in usuallyrecommended to prevent the recurrence of uratestones in dogs after cystotomy. Sodiumbicarbonate at 0.5 to 1.0 g is given orally thricedaily.

Acidification of urine

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Acidification of urine is used as a test for renaltubular acidosis. Acidification helps in theexcretion of certain drugs like amphetamine,phencyclidine, quinine etc.

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Ammonium chloride, ascorbic acid or calciumchloride can be used to acidify urine. • Ammoniumchloride (NH4Cl) is metabolised in the liver toNH4 and Cl- The Cl- is excreted along with Na+

The base conserving mechanisms secrete H+ and NH4 into the urine

Administration & uses•

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Acidification of urine is used as a test for renal tubular acidosis.Acidification helps in theexcretion of certain drugs like amphetamine, phencyclidine, quinineetc.• Ammonium chloride, ascorbic acid or calcium chloride can be usedto acidify urine.• Ammonium chloride (NH4Cl) is metabolised in the liver to NH andCl- the CTis excreted along with Na+. The base conserving mechanisms secrete H+ and NH4 into the urine

Administration & uses

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Acidification increases action of hexamine,penicillins and tetracyclines in the treatmentof urinary tract infections.• Acidification increases excretion of basic drugslike Pethidine and amphetamine

Ecbolics

• These are agents that bring about increase inuterine contractions.

Oxytocin

• It is hormone of the posterior pituitary receivedfrom the hypothalamus. It has a Majorphysiological role in milk let down and laborinitiation.

Clincals use of Oxytocin

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For labor induction. Given by slow I/v in dextrosesolution.� For mIlk letdown . Only in agalactic animals

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For treatment of uterine inertia and for rapdinvolution of uterus.� To arrest postparturient haemorrhage.� For expulsion of retained placenta.o The dose of oxytocin is 5 - 25 units in bitch, 75 -100 units in cow / mare and 30 -50 units in sow / ewe

Oxytocics

• Other agents which perform similar functionsare also called oxytocics.

Ergot alkaloids

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: Alkaloids from the fungus Claviveps purpurea viz.ergometrine, ergonovine have prominent effect onthe uterus. Not preferred for induction of labour.Generally indicated for postparturienthaemorrhage, rapid involution of uterus, retaineplacenta.

PGF ALPHA 2

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Exerts potent stimulant action on myometrium. Itis also popularly used forits luteolytic effect

Tocolytic

• These are agents that inhibit uterinecontractions. They relax uterine smmothmuscle and may be used to delay labor and tostop threatened abortion.

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Beta2 agonists: Salbutamol, terbutaline, isoxsuprine• Calcium channel blockers: Nifedipine, diltiazem• Oxytocin antagonist: Atosiban

Fluid therapy

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Fluid therapy refers to administration of fluids tocompensate the loss of fluids from thebody due to a variety of conditions leading todehydration. Fluid loss in the body can leadto shock and can become fatal if unattended

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The purpose of fluid therapy is to correctdehydration or overhydration, elctrolyteimbalance and /or acid -base imbalance.

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It is also indicated to correct acidosis/alkalosis,treat shock, give parenteral nourishmentor even stimulate organ function such as kidney.

Fluid volume & type

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The type of solution is to be dictated by history,clinical signs and laboratory examination.• The volume of fluid is determined the need formaintenance as well as the need forreplacement of lost fluid.

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For normal maintenance, a thumb rule of 65 ml /kg /24 hr for adults and 130 ml / kg /24hr for young ones is calculated.

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Based on this, a normal mature dog of 20 kg wouldrequire 1300 ml for 24hr period.• Replacement of fluid loss must be in addition tothe maintenance requirement.• To calculate fluid loss one must estimate thedegree of dehydration.

Choice of fluid