Succinylcholine, or Suxamethonium chloride, is an 'interesting choice' for this kind or purpose.
As a muscle relaxant with a relatively short duration it will paralyse the victim, cause breathing to stop and then death. Depending on dosage and wether your perpetrator carries a breathing apparatus for mechanical ventilation with him.
If the victim remains conscious she will feel extremely helpless and terrified on the psychological side. Physical reactions during or afterwards might include:
- Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
- Signs of a high potassium level like a heartbeat that does not feel normal; - change in thinking clearly and with logic; feeling weak, lightheaded, or dizzy; feel like passing out; numbness or tingling; or shortness of breath.
- Slow heartbeat.
- Very bad dizziness or passing out.
- Very bad headache.
- Muscle pain.
- Not able to pass urine or change in how much urine is passed.
- A heartbeat that does not feel normal.
- Chest pain or pressure.
- More eye pressure.
- Trouble breathing, slow breathing, or shallow breathing.
- This medicine may cause a very bad and sometimes deadly problem called malignant hyperthermia. Call your doctor right away if you have a fast heartbeat, fast breathing, fever, or spasm or stiffness of the jaw muscles.
(From: drugs.com/succinylcholine more personal "review" stories found here)
But the fun doesn't stop there. From
Generic Name: succinylcholine chloride
Brand Name: Anectine:
The average dose required to produce neuromuscular blockade and to facilitate tracheal intubation is 0.6 mg/kg ANECTINE (succinylcholine chloride) Injection given intravenously. The optimum dose will vary among individuals and may be from 0.3 to 1.1 mg/kg for adults. Following administration of doses in this range, neuromuscular blockade develops in about 1 minute; maximum blockade may persist for about 2 minutes, after which recovery takes place within 4 to 6 minutes. However, very large doses may result in more prolonged blockade. A 5- to 10-mg test dose may be used to determine the sensitivity of the patient and the individual recovery time. […] The dose of succinylcholine administered by infusion depends upon the duration of the surgical procedure and the need for muscle relaxation. The average rate for an adult ranges between 2.5 and 4.3 mg per minute.
Adverse reactions to succinylcholine consist primarily of an extension of its pharmacological actions. Succinylcholine causes profound muscle relaxation resulting in respiratory depression to the point of apnea; this effect may be prolonged. Hypersensitivity reactions, including anaphylaxis, may occur in rare instances. The following additional adverse reactions have been reported: cardiac arrest, malignant hyperthermia, arrhythmias, bradycardia, tachycardia, hypertension, hypotension, hyperkalemia, prolonged respiratory depression or apnea, increased intraocular pressure, muscle fasciculation, jaw rigidity, postoperative muscle pain, rhabdomyolysis with possible myoglobinuric acute renal failure, excessive salivation, and rash.
There have been post-marketing reports of severe allergic reactions (anaphylactic and anaphylactoid reactions) associated with use of neuromuscular blocking agents, including ANECTINE (succinylcholine chloride) . These reactions, in some cases, have been life-threatening and fatal. Because these reactions were reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency
SUCCINYLCHOLINE SHOULD BE USED ONLY BY THOSE SKILLED IN THE MANAGEMENT OF ARTIFICIAL RESPIRATION AND ONLY WHEN FACILITIES ARE INSTANTLY AVAILABLE FOR TRACHEAL INTUBATION AND FOR PROVIDING ADEQUATE VENTILATION OF THE PATIENT, INCLUDING THE ADMINISTRATION OF OXYGEN UNDER POSITIVE PRESSURE AND THE ELIMINATION OF CARBON DIOXIDE. THE CLINICIAN MUST BE PREPARED TO ASSIST OR CONTROL RESPIRATION.
TO AVOID DISTRESS TO THE PATIENT, SUCCINYLCHOLINE SHOULD NOT BE ADMINISTERED BEFORE UNCONSCIOUSNESS HAS BEEN INDUCED. IN EMERGENCY SITUATIONS, HOWEVER, IT MAY BE NECESSARY TO ADMINISTER SUCCINYLCHOLINE BEFORE UNCONSCIOUSNESS IS INDUCED.
SUCCINYLCHOLINE IS METABOLIZED BY PLASMA CHOLINESTERASE AND SHOULD BE USED WITH CAUTION, IF AT ALL, IN PATIENTS KNOWN TO BE OR SUSPECTED OF BEING HOMOZYGOUS FOR THE ATYPICAL PLASMA CHOLINESTERASE GENE.
In conclusion: this will not work very well. Relatively safe and effective in the hands of experts and the right setting, in a criminal plan this will lead to disaster if the plan didn't involve sending the kidnapping victim back in pieces from the start. If you insist on using this drug: for similar effects you might look at curare's effects, which might be easier to come by.