INDICATIONS     CONTRA-INDICATIONS     DOSAGE     SIDE-EFFECTS     PREGNANCY     OVERDOSE     IDENTIFICATION     PATIENT INFORMATION

Logo HYPOTEN L
SCHEDULING STATUS:
S4

PROPRIETARY NAME
(and dosage form):

HYPOTEN L
Freeze-dried powder

COMPOSITION:
Per vial:
Sodium nitroprusside         100 mg

PHARMACOLOGICAL CLASSIFICATION:
A. 7.1.3 Other hypotensives

PHARMACOLOGICAL ACTION:
Sodium Nitroprusside (Hypoten L) is a powerful vasodilator. The effects of the nitroprusside ion are similar to those of nitrite, in that it acts directly on the smooth muscle of blood vessels - probably due to the Fe-NO grouping. Both resistance and capacitance vessels are affected. Vascular resistance is decreased less in the renal than in the femoral and mesenteric vascular beds. The effects of nitroprusside are quite transient, due to its rapid conversion in the body to thiocyanate. The effect of nitroprusside on smooth muscle other than vascular is not known.

INDICATIONS:
For the immediate reduction of blood pressure as emergency treatment for patients in hypertensive encephalopathy, intracranial haemorrhage, head injury, hypertension complicated by acute heart failure and associated pulmonary edema, pheochromocytoma and toxemia of pregnancy. In skilled and experienced hands Hypoten L may be used for controlled hypotension during surgery where the technique is clearly indicated. Hypoten L can improve left vertricular function following acute myocardial infarction. It has had a preliminary but encouraging trial in patients with chronic refractory heart failure.

CONTRA-INDICATIONS:
Hypoten L should not be used in the treatment of compensatory hypertension, e.g. arteriovenous shunt, coarctation of aorta nor is it indicated for chronic use. Hypoten L should not be given to children until its safety, proper administration and dosage for paediatric use have been determined.

DOSAGE AND DIRECTIONS FOR USE:
Dissolve the contents of one vial in 5 mL of sterile dextrose solution and dilute to 1000 mL with sterile dextrose solution. The diluted solution is infused at a rate of 5 - 150 drops per minute until the desired systolic pressure is obtained. Blood pressure will return to normal 6 - 10 minutes after discontinuing the infusion.
The hypotensive response to Hypoten L is very rapid, as is the rise in blood pressure on stopping the infusion. Therefore adequate facilities in terms of personnel and equipment for frequent monitoring of blood pressure should be available. Because of its rapid onset of action and its potency, Hypoten L should preferably be administered by devices that could allow precise adjustment of the flow rate such as an infusion pump or microdrip regulator. Dilutions of Hypoten L should not be kept for longer than 4 hours. If the infusion is highly coloured (blue, green or dark red), it must be discarded. Solutions should be protected from light.

SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Nausea, retching, diaphoresis, headache, palpitations, dizziness, apprehension, muscle twitching, retrosternal discomfort and abdominal pain have been observed. All these symptoms disappear with appropriate slowing or temporary interruption of the infusion. If excessive amounts of Hypoten L are given, collapse as well as toxic side effects (e.g. tinnitus, blurred vision, delirium) may occur as a result of too high plasma thiocyanate levels, although these symptoms may also be due to the underlying disease. Determination of the thiocyanate concentration may help in determining the cause. With gross overdosages, cyanide intoxication is possible (dizziness, rapid breathing, headache, sleepiness, tachycardia, unconsciousness, cramps). The safety of Hypoten L for women who are pregnant or in whom pregnancy cannot be ruled out has not been established. It should therefore be used in such cases only after the expected therapeutic benefit to the mother has been weighed against the possible hazard to the fetus. Hypoten L should be used with appropriate caution and initially in low doses for elderly patients since they may be more sensitive to the drug's hypotensive effects.
Ganglionic blocking agents are known to augment the hypotensive effect of Hypoten L. During infusion the heartrate and bloodpressure must be carefully monitored. Thiocyanate inhibits both uptake and binding of iodine. Therefore use caution in giving the preparation to patients with hypothyroidism. Elimination of thiocyanate is dependant on adequate renal function and so care must be exercised in patients with severe renal insufficiency, for extended treatment of such patients, blood levels of thiocyanate should be determined daily and should not exceed 10 mg per 100 mL.

KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
The first signs of sodium nitroprusside overdosage are those of profound hypotension. Metabolic acidosis may be an early indication of this overdosage. This may be associated with or followed by dyspnea, headache, vomiting, dizziness, ataxia and loss of consciousness. Sodium nitroprusside should then be immediately discontinued.
Massive overdosage may also produce signs similar to those of cyanide poisoning with coma, imperceptible pulse, absent reflexes, widely dilated pupils, pink colour, distant heart sounds, hypotension and very shallow breathing. Oxygen alone will not provide relief. Nitrites should be administered to induce methemoglobin formation. Methemoglobin in turn, combines with cyanide bound to cytochrome oxidase to liberate cytrochrome oxidase and form a non-toxic complex, cyanmethemoglobin. Cyanide then gradually dissociates from the latter and is converted by administration of thiosulphate to sodium thiocyanate in the presence of rhodanese.
Treatment:
In cases of massive overdosage when signs of cyanide toxicity are present use the following regimen:
1. Discontinue administration of Hypoten L.
2. Administer amyl nitrite inhalations for 15 - 30 seconds each minute until a 3 % sodium nitrite solution can be prepared for administration.
3. Sodium nitrite 3 % solution should be injected intravenously at a rate not exceeding 2,5 -5,0 mL/minute up to a total dose of 10 - 15 mL with careful monitoring of the blood pressure.
4. Following the above steps, inject sodium thiosulphate intravenously 12,5 g in 50 mL of 5 % dextrose in water over a 10 minute period.
5. Since signs of overdosage may reappear, the patient must be observed for several hours.
6. If signs of overdosage reappear, sodium nitrite and sodium thiosulphate injections are repeated at one-half of the above doses.
7. During the administration of nitrites and later when thiocyanate formation is taking place blood pressure may drop but can be corrected with vasopressor agents.

IDENTIFICATION:
Orange brown plug in amber vial.

PRESENTATION:
Vials each containing 100 mg sodium nitroprusside. Packed in outer containers containing 10 vials.

STORAGE INSTRUCTIONS:
Store at 4°C. Protect from light. The solution should be protected from light and must be destroyed 4 hours after preparation.
KEEP OUT OF REACH OF CHILDREN.

REGISTRATION NUMBER:
G/7.1.3/1

NAME AND BUSINESS ADDRESS OF THE APPLICANT:
ADCOCK INGRAM LIMITED
Adcock Ingram Park
17 Harrison Avenue
Bryanston Ext. 77
Private Bag X69
Bryanston, 2021

DATE OF PUBLICATION OF THIS PACKAGE INSERT:
13 June 1974

New addition to this site: May 2004
Source: Pharmaceutical Industry

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