Definition of Vertigo: Vertigo, or dizziness, usually results from a disorder in the peripheral vestibular system (i.e., structures of the inner ear). Dizziness also may occur as a result of a disorder in the central vestibular system (i.e., vestibular nerve, brainstem, and cerebellum). In some cases, the cause of vertigo is unknown.

From what you describe, it does sound like the symptoms of an inner ear disorder.  However, if you suffered an injury in your spine, neck, and/or head, this could also cause your symptoms.  You may want to find a good chiropractor to help in this situation.  Also, there is also the chance that whatever your drink was spiked with could have affected the central vestibular system in some way.  One last question, since this incident, have you experiences a marked increase in unexplainable anxiety?  This is another cause of vertigo.

I am going to leave you with the following natural guidelines in dealing with vertigo.  Please take care, and I wish you the very best.

Diet: Avoid caffeine, chocolates, salt, fried foods, nicotine, drugs, alcohol, and aspartame (NutraSweet(TM)).

Flower Essences: Rescue Remedy® is useful for calming accompanying stress. Scleranthus can also be helpful.

Herbs: Ginkgo biloba and ginger can be helpful. Take one 40 mg tablet of ginkgo or two capsules of ginger three times a day.

Homeopathy: Useful homeopathic remedies include Gelsemium, Phosphorus, Cocculus, Aconite, Nat. mur., Sulfur, Silicea, Lycopodium, and Belladonna.

Lifestyle: Stay still during vertigo attacks and avoid rapid body movements, especially of the head. Be sure to reduce stress, and get adequate sleep.

Nutritional Supplementation: Recommended nutrients include Vitamin B complex, vitamin B3 (niacin), vitamin B6, vitamin C plus bioflavonoids and rutin, vitamin E, calcium, choline, and adrenal glandulars.

Alternative Professional Care
If your symptoms persist despite the above measures, seek the help of a qualified health professional. The following professional care therapies have all been shown to be useful for treating vertigo: Acupressure, Acupuncture, Ayurveda, Bodywork, Chiropractic, Craniosacral Therapy, Environmental Medicine, Hypnotherapy, Magnetic Field Therapy, Naturopathic Medicine, Osteopathy, Qigong, Reflexology, and Traditional Chinese Medicine

I spoke with a chiropractor about this for a friend about a week ago.  She has benign positional vertigo and he told me that although she could go in for the Epley manuever she could just as easily perform the exercises at home, if they helped she would know she was correctly diagnosed, if not, she could see if there were some type of misalignment that needed adjustment.  Here is an article that talks about it and gives direction for the exercises...try these and see if it helps.

http://www.tchain.com/otoneurology/disorders/bppv/bppv.html

Interestingly enough, one of the medicinal uses for oleander is against vertigo.  An ethanolic extract of oleander called solutio neriolini is used in Russia for both vertigo and congestive heart symptoms.

Tony