Source and chemistry
Natural alkaloid obtained from root of plant “rauwolfia serpentina” (snake root) which is abundant in the subcontinent (“chandan booti”)
Non polar, so can cross BBB rapidly. Central and peripheral action occurs (unlike guanethidine).
Mechanism of action
- Acting on Mg++- ATP pump, blocks it irreversibly (which is required for uptake of biogenic amines from cytoplasm into storage vesicles), thus depletion and decreased uptake of biogenic amines occurs in both central and peripheral neurons. As a result degradation of biogenic amines occurs.
- Serotonin decreased
- Conversion of dopamine into NE cannot take place, so synthesis of VMAT s required.
The drug crosses blood brain barrier.
Decreases blood pressure. The fall is gradual as the drug blocks storage pumps both centrally and peripherally acting drug. Surprisingly no or mild postural hypotension is seen. This is because centrally acting drugs do not produce postural hypotension. Baroreceptor sensitivity is increased even further (some spare baroreceptors).
Decrease in dopamine produces antipsychotic effects
Decrease in NE produces antihypertensive effects
Decrease in serotonin produces antiemetic effects.
1. Hypertension (0.25 mg/day very low dose)
Two entities affect CNS, depression on one hand and psychosis on other. Depression is because of decrease in biogenic amines while psychosis is always due to increase in number of biogenic amines (amphetamines). All drugs or conditions decreasing the levels produce depression. Reserpine depletes the stores of these biogenic amines, and was used in older days as antipsychotic.
3. Anti emetic
- depression (producing suicidal tendencies, one reason why use discontinued)
- extra pyramidal effects decreasing the levels of biogenic amines in nigrostriatal pathway (due to decrease in dopamine, parkinsonism like symptoms)
(block sympathetic system peripherally)
- Acidity (contraindicated in ulcers)
(due to increased blood flow)
Decrease in libido
Interferes with action of drugs used in Parkinsonism like levo dopa.
|M.A.O- Reuptake 1||Blockage Mg++ ATP pump|
|Pharmacological Actions- tiphasic, biphasic, monophasic response||Gradual fall in blood pressure|
|Postural hypotension||No or mild postural hypotension|
|No suicidal tendencies||Suicidal tendencies|