Agriculture Reference
In-Depth Information
Clinical Properties — Rauwolfia is undoubtedly the most effective and the most widely used
plant antihypertensive agent. The drug exerts its hypotensive effects slowly, but the effects persist
for a few weeks. Rauwolfia therapy produces reduction of congestion of the head, vertigo, cardiac
oppression, and general restlessness. 10 Although Rauwolfia is very effective in controlling most of
the symptomatic manifestations of hypertension, adequate reduction in blood pressure is achieved
in only about 40% of mild and 30% of medium-severe cases of hypertension. 10 The drug cannot
compete with the more powerful ganglion-blocking agents (such as guanethidine and hexametho-
nium) in the treatment of severe and malignant hypertension. Rauwolfia is not suitable for such
conditions and for cases requiring rapid lowering of the blood pressure.
The drug has been formulated with β-blockers, diuretics, or convallaria glycosides. In summary,
the clinical indications of Rauwolfia are as follows:
1. It is the drug of choice in medium-severe primary hypertension. The drug should be given over a
prolonged period, usually up to 6 months and even 1 year.
2. It is effective as an oral antihypertensive but has slow onset of action. The usual regimen is to begin
therapy with small doses followed by a gradual dose increase until there is a reduction in blood pres-
sure or the advent of undesirable side effects, which will necessitate lowering the dose.
3. For hypertension therapy, it has the advantage of oral administration and is available in many bio-
equivalent dosage forms.
4. Rauwolfia is neither a cure for hypertension nor a prophylaxis for the progression of the disease. At
a dose of 2-6 mg of the crude drug in divided doses, Rauwolfia ameliorates most of the subjective
symptoms of hypertension.
The drug is available in the following forms:
1. Powdered Rauwolfia serpentine ( U.S. Pharmacopoeia ; Indian Pharmacopoeia ): This consists of
R. serpentine roots reduced to fine or very fine powder and adjusted to contain 0.15% to 0.2% of
reserpine-like alkaloids, calculated as reserpine.
2. Rauwolfia dry extract ( Indian Pharmacopoeia ): The drug is prepared by percolation of roots of R.
serpentine with 90% of alcohol and the percolate concentrated under reduced pressure (<60°C) to
yield a soft extract. The product is adsorbed to starch and dried. It is standardized to contain 4% w/w
of total Rauwolfia alkaloids; the usual dose is 15 to 16 mg.
3. Rauwolfia liquid extract ( Indian Pharmacopoeia ): This is prepared by percolation as in item 2, but
no starch is added, and it is not concentrated. The standardized extract contains 1% w/v of the total
alkaloids; the dose is 0.2 to 0.5 ml.
4. Alseroxylon: This is the feebly basic fraction of the alcoholic extract of Rauwolfia containing reser-
pine rescinnamine and deserpidine. The standardized drug contains at least 5 mg/ml of reserpine-
like alkaloids.
Pharmacokinetics — When ingested, Rauwolfia is slow in onset of antihypertensive effects
due to the time required (several days) to deplete existing stores of norepinephrine. One week or
more may be required to realize the full antihypertensive effect of drug.
Toxicity — Rauwolfia alkaloids are known to cause mental depression, which may persist for
several months after the drug has been withdrawn. The drug should be discontinued at the first sign
of despondency, early morning insomnia, loss of appetite, impotence, or self-deprecation. Severe
cases resulting in maniac depression or suicidal tendencies are extremely rare. The drug is contrain-
dicated in patients with a past history of bronchial asthma or allergy, active peptic ulcer, ulcerative
colitis, or pheochromocytoma and in patients receiving electroconvulsive therapy. The safety and
efficacy of its use in pregnancy, lactation, and children have not been established. Chronic toxicity
and interaction with other drugs are similar to reserpine.
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